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2 T H E /proc F I L E S Y S T E M
3 ------------------------------------------------------------------------------
4 /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
7 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9 ------------------------------------------------------------------------------
10 Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12 ------------------------------------------------------------------------------
13 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
15 Table of Contents
16 -----------------
18 0 Preface
19 0.1 Introduction/Credits
20 0.2 Legal Stuff
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
24 1.2 Kernel data
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
27 1.5 SCSI info
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
33 2 Modifying System Parameters
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
37 score
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45 3.9 /proc/<pid>/map_files - Information about memory mapped files
46 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
48 4 Configuring procfs
49 4.1 Mount options
51 ------------------------------------------------------------------------------
52 Preface
53 ------------------------------------------------------------------------------
55 0.1 Introduction/Credits
56 ------------------------
58 This documentation is part of a soon (or so we hope) to be released book on
59 the SuSE Linux distribution. As there is no complete documentation for the
60 /proc file system and we've used many freely available sources to write these
61 chapters, it seems only fair to give the work back to the Linux community.
62 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
63 afraid it's still far from complete, but we hope it will be useful. As far as
64 we know, it is the first 'all-in-one' document about the /proc file system. It
65 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
66 SPARC, AXP, etc., features, you probably won't find what you are looking for.
67 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
68 additions and patches are welcome and will be added to this document if you
69 mail them to Bodo.
71 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
72 other people for help compiling this documentation. We'd also like to extend a
73 special thank you to Andi Kleen for documentation, which we relied on heavily
74 to create this document, as well as the additional information he provided.
75 Thanks to everybody else who contributed source or docs to the Linux kernel
76 and helped create a great piece of software... :)
78 If you have any comments, corrections or additions, please don't hesitate to
79 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
80 document.
82 The latest version of this document is available online at
83 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
85 If the above direction does not works for you, you could try the kernel
86 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
87 comandante@zaralinux.com.
89 0.2 Legal Stuff
90 ---------------
92 We don't guarantee the correctness of this document, and if you come to us
93 complaining about how you screwed up your system because of incorrect
94 documentation, we won't feel responsible...
96 ------------------------------------------------------------------------------
97 CHAPTER 1: COLLECTING SYSTEM INFORMATION
98 ------------------------------------------------------------------------------
100 ------------------------------------------------------------------------------
101 In This Chapter
102 ------------------------------------------------------------------------------
103 * Investigating the properties of the pseudo file system /proc and its
104 ability to provide information on the running Linux system
105 * Examining /proc's structure
106 * Uncovering various information about the kernel and the processes running
107 on the system
108 ------------------------------------------------------------------------------
111 The proc file system acts as an interface to internal data structures in the
112 kernel. It can be used to obtain information about the system and to change
113 certain kernel parameters at runtime (sysctl).
115 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
116 show you how you can use /proc/sys to change settings.
118 1.1 Process-Specific Subdirectories
119 -----------------------------------
121 The directory /proc contains (among other things) one subdirectory for each
122 process running on the system, which is named after the process ID (PID).
124 The link self points to the process reading the file system. Each process
125 subdirectory has the entries listed in Table 1-1.
128 Table 1-1: Process specific entries in /proc
129 ..............................................................................
130 File Content
131 clear_refs Clears page referenced bits shown in smaps output
132 cmdline Command line arguments
133 cpu Current and last cpu in which it was executed (2.4)(smp)
134 cwd Link to the current working directory
135 environ Values of environment variables
136 exe Link to the executable of this process
137 fd Directory, which contains all file descriptors
138 maps Memory maps to executables and library files (2.4)
139 mem Memory held by this process
140 root Link to the root directory of this process
141 stat Process status
142 statm Process memory status information
143 status Process status in human readable form
144 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
145 symbol the task is blocked in - or "0" if not blocked.
146 pagemap Page table
147 stack Report full stack trace, enable via CONFIG_STACKTRACE
148 smaps an extension based on maps, showing the memory consumption of
149 each mapping and flags associated with it
150 numa_maps an extension based on maps, showing the memory locality and
151 binding policy as well as mem usage (in pages) of each mapping.
152 ..............................................................................
154 For example, to get the status information of a process, all you have to do is
155 read the file /proc/PID/status:
157 >cat /proc/self/status
158 Name: cat
159 State: R (running)
160 Tgid: 5452
161 Pid: 5452
162 PPid: 743
163 TracerPid: 0 (2.4)
164 Uid: 501 501 501 501
165 Gid: 100 100 100 100
166 FDSize: 256
167 Groups: 100 14 16
168 VmPeak: 5004 kB
169 VmSize: 5004 kB
170 VmLck: 0 kB
171 VmHWM: 476 kB
172 VmRSS: 476 kB
173 RssAnon: 352 kB
174 RssFile: 120 kB
175 RssShmem: 4 kB
176 VmData: 156 kB
177 VmStk: 88 kB
178 VmExe: 68 kB
179 VmLib: 1412 kB
180 VmPTE: 20 kb
181 VmSwap: 0 kB
182 HugetlbPages: 0 kB
183 Threads: 1
184 SigQ: 0/28578
185 SigPnd: 0000000000000000
186 ShdPnd: 0000000000000000
187 SigBlk: 0000000000000000
188 SigIgn: 0000000000000000
189 SigCgt: 0000000000000000
190 CapInh: 00000000fffffeff
191 CapPrm: 0000000000000000
192 CapEff: 0000000000000000
193 CapBnd: ffffffffffffffff
194 NoNewPrivs: 0
195 Seccomp: 0
196 voluntary_ctxt_switches: 0
197 nonvoluntary_ctxt_switches: 1
199 This shows you nearly the same information you would get if you viewed it with
200 the ps command. In fact, ps uses the proc file system to obtain its
201 information. But you get a more detailed view of the process by reading the
202 file /proc/PID/status. It fields are described in table 1-2.
204 The statm file contains more detailed information about the process
205 memory usage. Its seven fields are explained in Table 1-3. The stat file
206 contains details information about the process itself. Its fields are
207 explained in Table 1-4.
209 (for SMP CONFIG users)
210 For making accounting scalable, RSS related information are handled in an
211 asynchronous manner and the value may not be very precise. To see a precise
212 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
213 It's slow but very precise.
215 Table 1-2: Contents of the status files (as of 4.8)
216 ..............................................................................
217 Field Content
218 Name filename of the executable
219 Umask file mode creation mask
220 State state (R is running, S is sleeping, D is sleeping
221 in an uninterruptible wait, Z is zombie,
222 T is traced or stopped)
223 Tgid thread group ID
224 Ngid NUMA group ID (0 if none)
225 Pid process id
226 PPid process id of the parent process
227 TracerPid PID of process tracing this process (0 if not)
228 Uid Real, effective, saved set, and file system UIDs
229 Gid Real, effective, saved set, and file system GIDs
230 FDSize number of file descriptor slots currently allocated
231 Groups supplementary group list
232 NStgid descendant namespace thread group ID hierarchy
233 NSpid descendant namespace process ID hierarchy
234 NSpgid descendant namespace process group ID hierarchy
235 NSsid descendant namespace session ID hierarchy
236 VmPeak peak virtual memory size
237 VmSize total program size
238 VmLck locked memory size
239 VmPin pinned memory size
240 VmHWM peak resident set size ("high water mark")
241 VmRSS size of memory portions. It contains the three
242 following parts (VmRSS = RssAnon + RssFile + RssShmem)
243 RssAnon size of resident anonymous memory
244 RssFile size of resident file mappings
245 RssShmem size of resident shmem memory (includes SysV shm,
246 mapping of tmpfs and shared anonymous mappings)
247 VmData size of private data segments
248 VmStk size of stack segments
249 VmExe size of text segment
250 VmLib size of shared library code
251 VmPTE size of page table entries
252 VmPMD size of second level page tables
253 VmSwap amount of swap used by anonymous private data
254 (shmem swap usage is not included)
255 HugetlbPages size of hugetlb memory portions
256 Threads number of threads
257 SigQ number of signals queued/max. number for queue
258 SigPnd bitmap of pending signals for the thread
259 ShdPnd bitmap of shared pending signals for the process
260 SigBlk bitmap of blocked signals
261 SigIgn bitmap of ignored signals
262 SigCgt bitmap of caught signals
263 CapInh bitmap of inheritable capabilities
264 CapPrm bitmap of permitted capabilities
265 CapEff bitmap of effective capabilities
266 CapBnd bitmap of capabilities bounding set
267 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
268 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
269 Cpus_allowed mask of CPUs on which this process may run
270 Cpus_allowed_list Same as previous, but in "list format"
271 Mems_allowed mask of memory nodes allowed to this process
272 Mems_allowed_list Same as previous, but in "list format"
273 voluntary_ctxt_switches number of voluntary context switches
274 nonvoluntary_ctxt_switches number of non voluntary context switches
275 ..............................................................................
277 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
278 ..............................................................................
279 Field Content
280 size total program size (pages) (same as VmSize in status)
281 resident size of memory portions (pages) (same as VmRSS in status)
282 shared number of pages that are shared (i.e. backed by a file, same
283 as RssFile+RssShmem in status)
284 trs number of pages that are 'code' (not including libs; broken,
285 includes data segment)
286 lrs number of pages of library (always 0 on 2.6)
287 drs number of pages of data/stack (including libs; broken,
288 includes library text)
289 dt number of dirty pages (always 0 on 2.6)
290 ..............................................................................
293 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
294 ..............................................................................
295 Field Content
296 pid process id
297 tcomm filename of the executable
298 state state (R is running, S is sleeping, D is sleeping in an
299 uninterruptible wait, Z is zombie, T is traced or stopped)
300 ppid process id of the parent process
301 pgrp pgrp of the process
302 sid session id
303 tty_nr tty the process uses
304 tty_pgrp pgrp of the tty
305 flags task flags
306 min_flt number of minor faults
307 cmin_flt number of minor faults with child's
308 maj_flt number of major faults
309 cmaj_flt number of major faults with child's
310 utime user mode jiffies
311 stime kernel mode jiffies
312 cutime user mode jiffies with child's
313 cstime kernel mode jiffies with child's
314 priority priority level
315 nice nice level
316 num_threads number of threads
317 it_real_value (obsolete, always 0)
318 start_time time the process started after system boot
319 vsize virtual memory size
320 rss resident set memory size
321 rsslim current limit in bytes on the rss
322 start_code address above which program text can run
323 end_code address below which program text can run
324 start_stack address of the start of the main process stack
325 esp current value of ESP
326 eip current value of EIP
327 pending bitmap of pending signals
328 blocked bitmap of blocked signals
329 sigign bitmap of ignored signals
330 sigcatch bitmap of caught signals
331 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
332 0 (place holder)
333 0 (place holder)
334 exit_signal signal to send to parent thread on exit
335 task_cpu which CPU the task is scheduled on
336 rt_priority realtime priority
337 policy scheduling policy (man sched_setscheduler)
338 blkio_ticks time spent waiting for block IO
339 gtime guest time of the task in jiffies
340 cgtime guest time of the task children in jiffies
341 start_data address above which program data+bss is placed
342 end_data address below which program data+bss is placed
343 start_brk address above which program heap can be expanded with brk()
344 arg_start address above which program command line is placed
345 arg_end address below which program command line is placed
346 env_start address above which program environment is placed
347 env_end address below which program environment is placed
348 exit_code the thread's exit_code in the form reported by the waitpid system call
349 ..............................................................................
351 The /proc/PID/maps file containing the currently mapped memory regions and
352 their access permissions.
354 The format is:
356 address perms offset dev inode pathname
358 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
359 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
360 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
361 a7cb1000-a7cb2000 ---p 00000000 00:00 0
362 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
363 a7eb2000-a7eb3000 ---p 00000000 00:00 0
364 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
365 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
366 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
367 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
368 a800b000-a800e000 rw-p 00000000 00:00 0
369 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
370 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
371 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
372 a8024000-a8027000 rw-p 00000000 00:00 0
373 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
374 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
375 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
376 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
377 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
379 where "address" is the address space in the process that it occupies, "perms"
380 is a set of permissions:
382 r = read
383 w = write
384 x = execute
385 s = shared
386 p = private (copy on write)
388 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
389 "inode" is the inode on that device. 0 indicates that no inode is associated
390 with the memory region, as the case would be with BSS (uninitialized data).
391 The "pathname" shows the name associated file for this mapping. If the mapping
392 is not associated with a file:
394 [heap] = the heap of the program
395 [stack] = the stack of the main process
396 [vdso] = the "virtual dynamic shared object",
397 the kernel system call handler
399 or if empty, the mapping is anonymous.
401 The /proc/PID/smaps is an extension based on maps, showing the memory
402 consumption for each of the process's mappings. For each of mappings there
403 is a series of lines such as the following:
405 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
406 Size: 1084 kB
407 Rss: 892 kB
408 Pss: 374 kB
409 Shared_Clean: 892 kB
410 Shared_Dirty: 0 kB
411 Private_Clean: 0 kB
412 Private_Dirty: 0 kB
413 Referenced: 892 kB
414 Anonymous: 0 kB
415 AnonHugePages: 0 kB
416 ShmemPmdMapped: 0 kB
417 Shared_Hugetlb: 0 kB
418 Private_Hugetlb: 0 kB
419 Swap: 0 kB
420 SwapPss: 0 kB
421 KernelPageSize: 4 kB
422 MMUPageSize: 4 kB
423 Locked: 0 kB
424 VmFlags: rd ex mr mw me dw
426 the first of these lines shows the same information as is displayed for the
427 mapping in /proc/PID/maps. The remaining lines show the size of the mapping
428 (size), the amount of the mapping that is currently resident in RAM (RSS), the
429 process' proportional share of this mapping (PSS), the number of clean and
430 dirty private pages in the mapping.
432 The "proportional set size" (PSS) of a process is the count of pages it has
433 in memory, where each page is divided by the number of processes sharing it.
434 So if a process has 1000 pages all to itself, and 1000 shared with one other
435 process, its PSS will be 1500.
436 Note that even a page which is part of a MAP_SHARED mapping, but has only
437 a single pte mapped, i.e. is currently used by only one process, is accounted
438 as private and not as shared.
439 "Referenced" indicates the amount of memory currently marked as referenced or
440 accessed.
441 "Anonymous" shows the amount of memory that does not belong to any file. Even
442 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
443 and a page is modified, the file page is replaced by a private anonymous copy.
444 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
445 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
446 huge pages.
447 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
448 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
449 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
450 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
451 For shmem mappings, "Swap" includes also the size of the mapped (and not
452 replaced by copy-on-write) part of the underlying shmem object out on swap.
453 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
454 does not take into account swapped out page of underlying shmem objects.
455 "Locked" indicates whether the mapping is locked in memory or not.
457 "VmFlags" field deserves a separate description. This member represents the kernel
458 flags associated with the particular virtual memory area in two letter encoded
459 manner. The codes are the following:
460 rd - readable
461 wr - writeable
462 ex - executable
463 sh - shared
464 mr - may read
465 mw - may write
466 me - may execute
467 ms - may share
468 gd - stack segment growns down
469 pf - pure PFN range
470 dw - disabled write to the mapped file
471 lo - pages are locked in memory
472 io - memory mapped I/O area
473 sr - sequential read advise provided
474 rr - random read advise provided
475 dc - do not copy area on fork
476 de - do not expand area on remapping
477 ac - area is accountable
478 nr - swap space is not reserved for the area
479 ht - area uses huge tlb pages
480 ar - architecture specific flag
481 dd - do not include area into core dump
482 sd - soft-dirty flag
483 mm - mixed map area
484 hg - huge page advise flag
485 nh - no-huge page advise flag
486 mg - mergable advise flag
488 Note that there is no guarantee that every flag and associated mnemonic will
489 be present in all further kernel releases. Things get changed, the flags may
490 be vanished or the reverse -- new added.
492 This file is only present if the CONFIG_MMU kernel configuration option is
493 enabled.
495 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
496 output can be achieved only in the single read call).
497 This typically manifests when doing partial reads of these files while the
498 memory map is being modified. Despite the races, we do provide the following
499 guarantees:
501 1) The mapped addresses never go backwards, which implies no two
502 regions will ever overlap.
503 2) If there is something at a given vaddr during the entirety of the
504 life of the smaps/maps walk, there will be some output for it.
507 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
508 bits on both physical and virtual pages associated with a process, and the
509 soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
510 To clear the bits for all the pages associated with the process
511 > echo 1 > /proc/PID/clear_refs
513 To clear the bits for the anonymous pages associated with the process
514 > echo 2 > /proc/PID/clear_refs
516 To clear the bits for the file mapped pages associated with the process
517 > echo 3 > /proc/PID/clear_refs
519 To clear the soft-dirty bit
520 > echo 4 > /proc/PID/clear_refs
522 To reset the peak resident set size ("high water mark") to the process's
523 current value:
524 > echo 5 > /proc/PID/clear_refs
526 Any other value written to /proc/PID/clear_refs will have no effect.
528 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
529 using /proc/kpageflags and number of times a page is mapped using
530 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
532 The /proc/pid/numa_maps is an extension based on maps, showing the memory
533 locality and binding policy, as well as the memory usage (in pages) of
534 each mapping. The output follows a general format where mapping details get
535 summarized separated by blank spaces, one mapping per each file line:
537 address policy mapping details
539 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
540 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
541 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
542 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
543 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
544 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
545 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
546 320698b000 default file=/lib64/libc-2.12.so
547 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
548 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
549 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
550 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
551 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
552 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
553 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
554 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
556 Where:
557 "address" is the starting address for the mapping;
558 "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
559 "mapping details" summarizes mapping data such as mapping type, page usage counters,
560 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
561 size, in KB, that is backing the mapping up.
563 1.2 Kernel data
564 ---------------
566 Similar to the process entries, the kernel data files give information about
567 the running kernel. The files used to obtain this information are contained in
568 /proc and are listed in Table 1-5. Not all of these will be present in your
569 system. It depends on the kernel configuration and the loaded modules, which
570 files are there, and which are missing.
572 Table 1-5: Kernel info in /proc
573 ..............................................................................
574 File Content
575 apm Advanced power management info
576 buddyinfo Kernel memory allocator information (see text) (2.5)
577 bus Directory containing bus specific information
578 cmdline Kernel command line
579 cpuinfo Info about the CPU
580 devices Available devices (block and character)
581 dma Used DMS channels
582 filesystems Supported filesystems
583 driver Various drivers grouped here, currently rtc (2.4)
584 execdomains Execdomains, related to security (2.4)
585 fb Frame Buffer devices (2.4)
586 fs File system parameters, currently nfs/exports (2.4)
587 ide Directory containing info about the IDE subsystem
588 interrupts Interrupt usage
589 iomem Memory map (2.4)
590 ioports I/O port usage
591 irq Masks for irq to cpu affinity (2.4)(smp?)
592 isapnp ISA PnP (Plug&Play) Info (2.4)
593 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
594 kmsg Kernel messages
595 ksyms Kernel symbol table
596 loadavg Load average of last 1, 5 & 15 minutes
597 locks Kernel locks
598 meminfo Memory info
599 misc Miscellaneous
600 modules List of loaded modules
601 mounts Mounted filesystems
602 net Networking info (see text)
603 pagetypeinfo Additional page allocator information (see text) (2.5)
604 partitions Table of partitions known to the system
605 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
606 decoupled by lspci (2.4)
607 rtc Real time clock
608 scsi SCSI info (see text)
609 slabinfo Slab pool info
610 softirqs softirq usage
611 stat Overall statistics
612 swaps Swap space utilization
613 sys See chapter 2
614 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
615 tty Info of tty drivers
616 uptime Wall clock since boot, combined idle time of all cpus
617 version Kernel version
618 video bttv info of video resources (2.4)
619 vmallocinfo Show vmalloced areas
620 ..............................................................................
622 You can, for example, check which interrupts are currently in use and what
623 they are used for by looking in the file /proc/interrupts:
625 > cat /proc/interrupts
626 CPU0
627 0: 8728810 XT-PIC timer
628 1: 895 XT-PIC keyboard
629 2: 0 XT-PIC cascade
630 3: 531695 XT-PIC aha152x
631 4: 2014133 XT-PIC serial
632 5: 44401 XT-PIC pcnet_cs
633 8: 2 XT-PIC rtc
634 11: 8 XT-PIC i82365
635 12: 182918 XT-PIC PS/2 Mouse
636 13: 1 XT-PIC fpu
637 14: 1232265 XT-PIC ide0
638 15: 7 XT-PIC ide1
639 NMI: 0
641 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
642 output of a SMP machine):
644 > cat /proc/interrupts
646 CPU0 CPU1
647 0: 1243498 1214548 IO-APIC-edge timer
648 1: 8949 8958 IO-APIC-edge keyboard
649 2: 0 0 XT-PIC cascade
650 5: 11286 10161 IO-APIC-edge soundblaster
651 8: 1 0 IO-APIC-edge rtc
652 9: 27422 27407 IO-APIC-edge 3c503
653 12: 113645 113873 IO-APIC-edge PS/2 Mouse
654 13: 0 0 XT-PIC fpu
655 14: 22491 24012 IO-APIC-edge ide0
656 15: 2183 2415 IO-APIC-edge ide1
657 17: 30564 30414 IO-APIC-level eth0
658 18: 177 164 IO-APIC-level bttv
659 NMI: 2457961 2457959
660 LOC: 2457882 2457881
661 ERR: 2155
663 NMI is incremented in this case because every timer interrupt generates a NMI
664 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
666 LOC is the local interrupt counter of the internal APIC of every CPU.
668 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
669 connects the CPUs in a SMP system. This means that an error has been detected,
670 the IO-APIC automatically retry the transmission, so it should not be a big
671 problem, but you should read the SMP-FAQ.
673 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
674 /proc/interrupts to display every IRQ vector in use by the system, not
675 just those considered 'most important'. The new vectors are:
677 THR -- interrupt raised when a machine check threshold counter
678 (typically counting ECC corrected errors of memory or cache) exceeds
679 a configurable threshold. Only available on some systems.
681 TRM -- a thermal event interrupt occurs when a temperature threshold
682 has been exceeded for the CPU. This interrupt may also be generated
683 when the temperature drops back to normal.
685 SPU -- a spurious interrupt is some interrupt that was raised then lowered
686 by some IO device before it could be fully processed by the APIC. Hence
687 the APIC sees the interrupt but does not know what device it came from.
688 For this case the APIC will generate the interrupt with a IRQ vector
689 of 0xff. This might also be generated by chipset bugs.
691 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
692 sent from one CPU to another per the needs of the OS. Typically,
693 their statistics are used by kernel developers and interested users to
694 determine the occurrence of interrupts of the given type.
696 The above IRQ vectors are displayed only when relevant. For example,
697 the threshold vector does not exist on x86_64 platforms. Others are
698 suppressed when the system is a uniprocessor. As of this writing, only
699 i386 and x86_64 platforms support the new IRQ vector displays.
701 Of some interest is the introduction of the /proc/irq directory to 2.4.
702 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
703 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
704 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
705 prof_cpu_mask.
707 For example
708 > ls /proc/irq/
709 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
710 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
711 > ls /proc/irq/0/
712 smp_affinity
714 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
715 IRQ, you can set it by doing:
717 > echo 1 > /proc/irq/10/smp_affinity
719 This means that only the first CPU will handle the IRQ, but you can also echo
720 5 which means that only the first and third CPU can handle the IRQ.
722 The contents of each smp_affinity file is the same by default:
724 > cat /proc/irq/0/smp_affinity
725 ffffffff
727 There is an alternate interface, smp_affinity_list which allows specifying
728 a cpu range instead of a bitmask:
730 > cat /proc/irq/0/smp_affinity_list
731 1024-1031
733 The default_smp_affinity mask applies to all non-active IRQs, which are the
734 IRQs which have not yet been allocated/activated, and hence which lack a
735 /proc/irq/[0-9]* directory.
737 The node file on an SMP system shows the node to which the device using the IRQ
738 reports itself as being attached. This hardware locality information does not
739 include information about any possible driver locality preference.
741 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
742 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
744 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
745 between all the CPUs which are allowed to handle it. As usual the kernel has
746 more info than you and does a better job than you, so the defaults are the
747 best choice for almost everyone. [Note this applies only to those IO-APIC's
748 that support "Round Robin" interrupt distribution.]
750 There are three more important subdirectories in /proc: net, scsi, and sys.
751 The general rule is that the contents, or even the existence of these
752 directories, depend on your kernel configuration. If SCSI is not enabled, the
753 directory scsi may not exist. The same is true with the net, which is there
754 only when networking support is present in the running kernel.
756 The slabinfo file gives information about memory usage at the slab level.
757 Linux uses slab pools for memory management above page level in version 2.2.
758 Commonly used objects have their own slab pool (such as network buffers,
759 directory cache, and so on).
761 ..............................................................................
763 > cat /proc/buddyinfo
765 Node 0, zone DMA 0 4 5 4 4 3 ...
766 Node 0, zone Normal 1 0 0 1 101 8 ...
767 Node 0, zone HighMem 2 0 0 1 1 0 ...
769 External fragmentation is a problem under some workloads, and buddyinfo is a
770 useful tool for helping diagnose these problems. Buddyinfo will give you a
771 clue as to how big an area you can safely allocate, or why a previous
772 allocation failed.
774 Each column represents the number of pages of a certain order which are
775 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
776 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
777 available in ZONE_NORMAL, etc...
779 More information relevant to external fragmentation can be found in
780 pagetypeinfo.
782 > cat /proc/pagetypeinfo
783 Page block order: 9
784 Pages per block: 512
786 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
787 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
788 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
789 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
790 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
791 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
792 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
793 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
794 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
795 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
796 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
798 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
799 Node 0, zone DMA 2 0 5 1 0
800 Node 0, zone DMA32 41 6 967 2 0
802 Fragmentation avoidance in the kernel works by grouping pages of different
803 migrate types into the same contiguous regions of memory called page blocks.
804 A page block is typically the size of the default hugepage size e.g. 2MB on
805 X86-64. By keeping pages grouped based on their ability to move, the kernel
806 can reclaim pages within a page block to satisfy a high-order allocation.
808 The pagetypinfo begins with information on the size of a page block. It
809 then gives the same type of information as buddyinfo except broken down
810 by migrate-type and finishes with details on how many page blocks of each
811 type exist.
813 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
814 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
815 make an estimate of the likely number of huge pages that can be allocated
816 at a given point in time. All the "Movable" blocks should be allocatable
817 unless memory has been mlock()'d. Some of the Reclaimable blocks should
818 also be allocatable although a lot of filesystem metadata may have to be
819 reclaimed to achieve this.
821 ..............................................................................
823 meminfo:
825 Provides information about distribution and utilization of memory. This
826 varies by architecture and compile options. The following is from a
827 16GB PIII, which has highmem enabled. You may not have all of these fields.
829 > cat /proc/meminfo
831 MemTotal: 16344972 kB
832 MemFree: 13634064 kB
833 MemAvailable: 14836172 kB
834 Buffers: 3656 kB
835 Cached: 1195708 kB
836 SwapCached: 0 kB
837 Active: 891636 kB
838 Inactive: 1077224 kB
839 HighTotal: 15597528 kB
840 HighFree: 13629632 kB
841 LowTotal: 747444 kB
842 LowFree: 4432 kB
843 SwapTotal: 0 kB
844 SwapFree: 0 kB
845 Dirty: 968 kB
846 Writeback: 0 kB
847 AnonPages: 861800 kB
848 Mapped: 280372 kB
849 Shmem: 644 kB
850 Slab: 284364 kB
851 SReclaimable: 159856 kB
852 SUnreclaim: 124508 kB
853 PageTables: 24448 kB
854 NFS_Unstable: 0 kB
855 Bounce: 0 kB
856 WritebackTmp: 0 kB
857 CommitLimit: 7669796 kB
858 Committed_AS: 100056 kB
859 VmallocTotal: 112216 kB
860 VmallocUsed: 428 kB
861 VmallocChunk: 111088 kB
862 AnonHugePages: 49152 kB
863 ShmemHugePages: 0 kB
864 ShmemPmdMapped: 0 kB
867 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
868 bits and the kernel binary code)
869 MemFree: The sum of LowFree+HighFree
870 MemAvailable: An estimate of how much memory is available for starting new
871 applications, without swapping. Calculated from MemFree,
872 SReclaimable, the size of the file LRU lists, and the low
873 watermarks in each zone.
874 The estimate takes into account that the system needs some
875 page cache to function well, and that not all reclaimable
876 slab will be reclaimable, due to items being in use. The
877 impact of those factors will vary from system to system.
878 Buffers: Relatively temporary storage for raw disk blocks
879 shouldn't get tremendously large (20MB or so)
880 Cached: in-memory cache for files read from the disk (the
881 pagecache). Doesn't include SwapCached
882 SwapCached: Memory that once was swapped out, is swapped back in but
883 still also is in the swapfile (if memory is needed it
884 doesn't need to be swapped out AGAIN because it is already
885 in the swapfile. This saves I/O)
886 Active: Memory that has been used more recently and usually not
887 reclaimed unless absolutely necessary.
888 Inactive: Memory which has been less recently used. It is more
889 eligible to be reclaimed for other purposes
890 HighTotal:
891 HighFree: Highmem is all memory above ~860MB of physical memory
892 Highmem areas are for use by userspace programs, or
893 for the pagecache. The kernel must use tricks to access
894 this memory, making it slower to access than lowmem.
895 LowTotal:
896 LowFree: Lowmem is memory which can be used for everything that
897 highmem can be used for, but it is also available for the
898 kernel's use for its own data structures. Among many
899 other things, it is where everything from the Slab is
900 allocated. Bad things happen when you're out of lowmem.
901 SwapTotal: total amount of swap space available
902 SwapFree: Memory which has been evicted from RAM, and is temporarily
903 on the disk
904 Dirty: Memory which is waiting to get written back to the disk
905 Writeback: Memory which is actively being written back to the disk
906 AnonPages: Non-file backed pages mapped into userspace page tables
907 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
908 Mapped: files which have been mmaped, such as libraries
909 Shmem: Total memory used by shared memory (shmem) and tmpfs
910 ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
911 with huge pages
912 ShmemPmdMapped: Shared memory mapped into userspace with huge pages
913 Slab: in-kernel data structures cache
914 SReclaimable: Part of Slab, that might be reclaimed, such as caches
915 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
916 PageTables: amount of memory dedicated to the lowest level of page
917 tables.
918 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
919 storage
920 Bounce: Memory used for block device "bounce buffers"
921 WritebackTmp: Memory used by FUSE for temporary writeback buffers
922 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
923 this is the total amount of memory currently available to
924 be allocated on the system. This limit is only adhered to
925 if strict overcommit accounting is enabled (mode 2 in
926 'vm.overcommit_memory').
927 The CommitLimit is calculated with the following formula:
928 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
929 overcommit_ratio / 100 + [total swap pages]
930 For example, on a system with 1G of physical RAM and 7G
931 of swap with a `vm.overcommit_ratio` of 30 it would
932 yield a CommitLimit of 7.3G.
933 For more details, see the memory overcommit documentation
934 in vm/overcommit-accounting.
935 Committed_AS: The amount of memory presently allocated on the system.
936 The committed memory is a sum of all of the memory which
937 has been allocated by processes, even if it has not been
938 "used" by them as of yet. A process which malloc()'s 1G
939 of memory, but only touches 300M of it will show up as
940 using 1G. This 1G is memory which has been "committed" to
941 by the VM and can be used at any time by the allocating
942 application. With strict overcommit enabled on the system
943 (mode 2 in 'vm.overcommit_memory'),allocations which would
944 exceed the CommitLimit (detailed above) will not be permitted.
945 This is useful if one needs to guarantee that processes will
946 not fail due to lack of memory once that memory has been
947 successfully allocated.
948 VmallocTotal: total size of vmalloc memory area
949 VmallocUsed: amount of vmalloc area which is used
950 VmallocChunk: largest contiguous block of vmalloc area which is free
952 ..............................................................................
954 vmallocinfo:
956 Provides information about vmalloced/vmaped areas. One line per area,
957 containing the virtual address range of the area, size in bytes,
958 caller information of the creator, and optional information depending
959 on the kind of area :
961 pages=nr number of pages
962 phys=addr if a physical address was specified
963 ioremap I/O mapping (ioremap() and friends)
964 vmalloc vmalloc() area
965 vmap vmap()ed pages
966 user VM_USERMAP area
967 vpages buffer for pages pointers was vmalloced (huge area)
968 N<node>=nr (Only on NUMA kernels)
969 Number of pages allocated on memory node <node>
971 > cat /proc/vmallocinfo
972 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
973 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
974 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
975 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
976 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
977 phys=7fee8000 ioremap
978 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
979 phys=7fee7000 ioremap
980 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
981 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
982 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
983 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
984 pages=2 vmalloc N1=2
985 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
986 /0x130 [x_tables] pages=4 vmalloc N0=4
987 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
988 pages=14 vmalloc N2=14
989 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
990 pages=4 vmalloc N1=4
991 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
992 pages=2 vmalloc N1=2
993 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
994 pages=10 vmalloc N0=10
996 ..............................................................................
998 softirqs:
1000 Provides counts of softirq handlers serviced since boot time, for each cpu.
1002 > cat /proc/softirqs
1003 CPU0 CPU1 CPU2 CPU3
1004 HI: 0 0 0 0
1005 TIMER: 27166 27120 27097 27034
1006 NET_TX: 0 0 0 17
1007 NET_RX: 42 0 0 39
1008 BLOCK: 0 0 107 1121
1009 TASKLET: 0 0 0 290
1010 SCHED: 27035 26983 26971 26746
1011 HRTIMER: 0 0 0 0
1012 RCU: 1678 1769 2178 2250
1015 1.3 IDE devices in /proc/ide
1016 ----------------------------
1018 The subdirectory /proc/ide contains information about all IDE devices of which
1019 the kernel is aware. There is one subdirectory for each IDE controller, the
1020 file drivers and a link for each IDE device, pointing to the device directory
1021 in the controller specific subtree.
1023 The file drivers contains general information about the drivers used for the
1024 IDE devices:
1026 > cat /proc/ide/drivers
1027 ide-cdrom version 4.53
1028 ide-disk version 1.08
1030 More detailed information can be found in the controller specific
1031 subdirectories. These are named ide0, ide1 and so on. Each of these
1032 directories contains the files shown in table 1-6.
1035 Table 1-6: IDE controller info in /proc/ide/ide?
1036 ..............................................................................
1037 File Content
1038 channel IDE channel (0 or 1)
1039 config Configuration (only for PCI/IDE bridge)
1040 mate Mate name
1041 model Type/Chipset of IDE controller
1042 ..............................................................................
1044 Each device connected to a controller has a separate subdirectory in the
1045 controllers directory. The files listed in table 1-7 are contained in these
1046 directories.
1049 Table 1-7: IDE device information
1050 ..............................................................................
1051 File Content
1052 cache The cache
1053 capacity Capacity of the medium (in 512Byte blocks)
1054 driver driver and version
1055 geometry physical and logical geometry
1056 identify device identify block
1057 media media type
1058 model device identifier
1059 settings device setup
1060 smart_thresholds IDE disk management thresholds
1061 smart_values IDE disk management values
1062 ..............................................................................
1064 The most interesting file is settings. This file contains a nice overview of
1065 the drive parameters:
1067 # cat /proc/ide/ide0/hda/settings
1068 name value min max mode
1069 ---- ----- --- --- ----
1070 bios_cyl 526 0 65535 rw
1071 bios_head 255 0 255 rw
1072 bios_sect 63 0 63 rw
1073 breada_readahead 4 0 127 rw
1074 bswap 0 0 1 r
1075 file_readahead 72 0 2097151 rw
1076 io_32bit 0 0 3 rw
1077 keepsettings 0 0 1 rw
1078 max_kb_per_request 122 1 127 rw
1079 multcount 0 0 8 rw
1080 nice1 1 0 1 rw
1081 nowerr 0 0 1 rw
1082 pio_mode write-only 0 255 w
1083 slow 0 0 1 rw
1084 unmaskirq 0 0 1 rw
1085 using_dma 0 0 1 rw
1088 1.4 Networking info in /proc/net
1089 --------------------------------
1091 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1092 additional values you get for IP version 6 if you configure the kernel to
1093 support this. Table 1-9 lists the files and their meaning.
1096 Table 1-8: IPv6 info in /proc/net
1097 ..............................................................................
1098 File Content
1099 udp6 UDP sockets (IPv6)
1100 tcp6 TCP sockets (IPv6)
1101 raw6 Raw device statistics (IPv6)
1102 igmp6 IP multicast addresses, which this host joined (IPv6)
1103 if_inet6 List of IPv6 interface addresses
1104 ipv6_route Kernel routing table for IPv6
1105 rt6_stats Global IPv6 routing tables statistics
1106 sockstat6 Socket statistics (IPv6)
1107 snmp6 Snmp data (IPv6)
1108 ..............................................................................
1111 Table 1-9: Network info in /proc/net
1112 ..............................................................................
1113 File Content
1114 arp Kernel ARP table
1115 dev network devices with statistics
1116 dev_mcast the Layer2 multicast groups a device is listening too
1117 (interface index, label, number of references, number of bound
1118 addresses).
1119 dev_stat network device status
1120 ip_fwchains Firewall chain linkage
1121 ip_fwnames Firewall chain names
1122 ip_masq Directory containing the masquerading tables
1123 ip_masquerade Major masquerading table
1124 netstat Network statistics
1125 raw raw device statistics
1126 route Kernel routing table
1127 rpc Directory containing rpc info
1128 rt_cache Routing cache
1129 snmp SNMP data
1130 sockstat Socket statistics
1131 tcp TCP sockets
1132 udp UDP sockets
1133 unix UNIX domain sockets
1134 wireless Wireless interface data (Wavelan etc)
1135 igmp IP multicast addresses, which this host joined
1136 psched Global packet scheduler parameters.
1137 netlink List of PF_NETLINK sockets
1138 ip_mr_vifs List of multicast virtual interfaces
1139 ip_mr_cache List of multicast routing cache
1140 ..............................................................................
1142 You can use this information to see which network devices are available in
1143 your system and how much traffic was routed over those devices:
1145 > cat /proc/net/dev
1146 Inter-|Receive |[...
1147 face |bytes packets errs drop fifo frame compressed multicast|[...
1148 lo: 908188 5596 0 0 0 0 0 0 [...
1149 ppp0:15475140 20721 410 0 0 410 0 0 [...
1150 eth0: 614530 7085 0 0 0 0 0 1 [...
1152 ...] Transmit
1153 ...] bytes packets errs drop fifo colls carrier compressed
1154 ...] 908188 5596 0 0 0 0 0 0
1155 ...] 1375103 17405 0 0 0 0 0 0
1156 ...] 1703981 5535 0 0 0 3 0 0
1158 In addition, each Channel Bond interface has its own directory. For
1159 example, the bond0 device will have a directory called /proc/net/bond0/.
1160 It will contain information that is specific to that bond, such as the
1161 current slaves of the bond, the link status of the slaves, and how
1162 many times the slaves link has failed.
1164 1.5 SCSI info
1165 -------------
1167 If you have a SCSI host adapter in your system, you'll find a subdirectory
1168 named after the driver for this adapter in /proc/scsi. You'll also see a list
1169 of all recognized SCSI devices in /proc/scsi:
1171 >cat /proc/scsi/scsi
1172 Attached devices:
1173 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1174 Vendor: IBM Model: DGHS09U Rev: 03E0
1175 Type: Direct-Access ANSI SCSI revision: 03
1176 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1177 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1178 Type: CD-ROM ANSI SCSI revision: 02
1181 The directory named after the driver has one file for each adapter found in
1182 the system. These files contain information about the controller, including
1183 the used IRQ and the IO address range. The amount of information shown is
1184 dependent on the adapter you use. The example shows the output for an Adaptec
1185 AHA-2940 SCSI adapter:
1187 > cat /proc/scsi/aic7xxx/0
1189 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1190 Compile Options:
1191 TCQ Enabled By Default : Disabled
1192 AIC7XXX_PROC_STATS : Disabled
1193 AIC7XXX_RESET_DELAY : 5
1194 Adapter Configuration:
1195 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1196 Ultra Wide Controller
1197 PCI MMAPed I/O Base: 0xeb001000
1198 Adapter SEEPROM Config: SEEPROM found and used.
1199 Adaptec SCSI BIOS: Enabled
1200 IRQ: 10
1201 SCBs: Active 0, Max Active 2,
1202 Allocated 15, HW 16, Page 255
1203 Interrupts: 160328
1204 BIOS Control Word: 0x18b6
1205 Adapter Control Word: 0x005b
1206 Extended Translation: Enabled
1207 Disconnect Enable Flags: 0xffff
1208 Ultra Enable Flags: 0x0001
1209 Tag Queue Enable Flags: 0x0000
1210 Ordered Queue Tag Flags: 0x0000
1211 Default Tag Queue Depth: 8
1212 Tagged Queue By Device array for aic7xxx host instance 0:
1213 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1214 Actual queue depth per device for aic7xxx host instance 0:
1215 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1216 Statistics:
1217 (scsi0:0:0:0)
1218 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1219 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1220 Total transfers 160151 (74577 reads and 85574 writes)
1221 (scsi0:0:6:0)
1222 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1223 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1224 Total transfers 0 (0 reads and 0 writes)
1227 1.6 Parallel port info in /proc/parport
1228 ---------------------------------------
1230 The directory /proc/parport contains information about the parallel ports of
1231 your system. It has one subdirectory for each port, named after the port
1232 number (0,1,2,...).
1234 These directories contain the four files shown in Table 1-10.
1237 Table 1-10: Files in /proc/parport
1238 ..............................................................................
1239 File Content
1240 autoprobe Any IEEE-1284 device ID information that has been acquired.
1241 devices list of the device drivers using that port. A + will appear by the
1242 name of the device currently using the port (it might not appear
1243 against any).
1244 hardware Parallel port's base address, IRQ line and DMA channel.
1245 irq IRQ that parport is using for that port. This is in a separate
1246 file to allow you to alter it by writing a new value in (IRQ
1247 number or none).
1248 ..............................................................................
1250 1.7 TTY info in /proc/tty
1251 -------------------------
1253 Information about the available and actually used tty's can be found in the
1254 directory /proc/tty.You'll find entries for drivers and line disciplines in
1255 this directory, as shown in Table 1-11.
1258 Table 1-11: Files in /proc/tty
1259 ..............................................................................
1260 File Content
1261 drivers list of drivers and their usage
1262 ldiscs registered line disciplines
1263 driver/serial usage statistic and status of single tty lines
1264 ..............................................................................
1266 To see which tty's are currently in use, you can simply look into the file
1267 /proc/tty/drivers:
1269 > cat /proc/tty/drivers
1270 pty_slave /dev/pts 136 0-255 pty:slave
1271 pty_master /dev/ptm 128 0-255 pty:master
1272 pty_slave /dev/ttyp 3 0-255 pty:slave
1273 pty_master /dev/pty 2 0-255 pty:master
1274 serial /dev/cua 5 64-67 serial:callout
1275 serial /dev/ttyS 4 64-67 serial
1276 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1277 /dev/ptmx /dev/ptmx 5 2 system
1278 /dev/console /dev/console 5 1 system:console
1279 /dev/tty /dev/tty 5 0 system:/dev/tty
1280 unknown /dev/tty 4 1-63 console
1283 1.8 Miscellaneous kernel statistics in /proc/stat
1284 -------------------------------------------------
1286 Various pieces of information about kernel activity are available in the
1287 /proc/stat file. All of the numbers reported in this file are aggregates
1288 since the system first booted. For a quick look, simply cat the file:
1290 > cat /proc/stat
1291 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1292 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1293 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1294 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1295 ctxt 1990473
1296 btime 1062191376
1297 processes 2915
1298 procs_running 1
1299 procs_blocked 0
1300 softirq 183433 0 21755 12 39 1137 231 21459 2263
1302 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1303 lines. These numbers identify the amount of time the CPU has spent performing
1304 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1305 second). The meanings of the columns are as follows, from left to right:
1307 - user: normal processes executing in user mode
1308 - nice: niced processes executing in user mode
1309 - system: processes executing in kernel mode
1310 - idle: twiddling thumbs
1311 - iowait: In a word, iowait stands for waiting for I/O to complete. But there
1312 are several problems:
1313 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1314 waiting for I/O to complete. When cpu goes into idle state for
1315 outstanding task io, another task will be scheduled on this CPU.
1316 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1317 on any CPU, so the iowait of each CPU is difficult to calculate.
1318 3. The value of iowait field in /proc/stat will decrease in certain
1319 conditions.
1320 So, the iowait is not reliable by reading from /proc/stat.
1321 - irq: servicing interrupts
1322 - softirq: servicing softirqs
1323 - steal: involuntary wait
1324 - guest: running a normal guest
1325 - guest_nice: running a niced guest
1327 The "intr" line gives counts of interrupts serviced since boot time, for each
1328 of the possible system interrupts. The first column is the total of all
1329 interrupts serviced including unnumbered architecture specific interrupts;
1330 each subsequent column is the total for that particular numbered interrupt.
1331 Unnumbered interrupts are not shown, only summed into the total.
1333 The "ctxt" line gives the total number of context switches across all CPUs.
1335 The "btime" line gives the time at which the system booted, in seconds since
1336 the Unix epoch.
1338 The "processes" line gives the number of processes and threads created, which
1339 includes (but is not limited to) those created by calls to the fork() and
1340 clone() system calls.
1342 The "procs_running" line gives the total number of threads that are
1343 running or ready to run (i.e., the total number of runnable threads).
1345 The "procs_blocked" line gives the number of processes currently blocked,
1346 waiting for I/O to complete.
1348 The "softirq" line gives counts of softirqs serviced since boot time, for each
1349 of the possible system softirqs. The first column is the total of all
1350 softirqs serviced; each subsequent column is the total for that particular
1351 softirq.
1354 1.9 Ext4 file system parameters
1355 -------------------------------
1357 Information about mounted ext4 file systems can be found in
1358 /proc/fs/ext4. Each mounted filesystem will have a directory in
1359 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1360 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1361 in Table 1-12, below.
1363 Table 1-12: Files in /proc/fs/ext4/<devname>
1364 ..............................................................................
1365 File Content
1366 mb_groups details of multiblock allocator buddy cache of free blocks
1367 ..............................................................................
1369 2.0 /proc/consoles
1370 ------------------
1371 Shows registered system console lines.
1373 To see which character device lines are currently used for the system console
1374 /dev/console, you may simply look into the file /proc/consoles:
1376 > cat /proc/consoles
1377 tty0 -WU (ECp) 4:7
1378 ttyS0 -W- (Ep) 4:64
1380 The columns are:
1382 device name of the device
1383 operations R = can do read operations
1384 W = can do write operations
1385 U = can do unblank
1386 flags E = it is enabled
1387 C = it is preferred console
1388 B = it is primary boot console
1389 p = it is used for printk buffer
1390 b = it is not a TTY but a Braille device
1391 a = it is safe to use when cpu is offline
1392 major:minor major and minor number of the device separated by a colon
1394 ------------------------------------------------------------------------------
1395 Summary
1396 ------------------------------------------------------------------------------
1397 The /proc file system serves information about the running system. It not only
1398 allows access to process data but also allows you to request the kernel status
1399 by reading files in the hierarchy.
1401 The directory structure of /proc reflects the types of information and makes
1402 it easy, if not obvious, where to look for specific data.
1403 ------------------------------------------------------------------------------
1405 ------------------------------------------------------------------------------
1406 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1407 ------------------------------------------------------------------------------
1409 ------------------------------------------------------------------------------
1410 In This Chapter
1411 ------------------------------------------------------------------------------
1412 * Modifying kernel parameters by writing into files found in /proc/sys
1413 * Exploring the files which modify certain parameters
1414 * Review of the /proc/sys file tree
1415 ------------------------------------------------------------------------------
1418 A very interesting part of /proc is the directory /proc/sys. This is not only
1419 a source of information, it also allows you to change parameters within the
1420 kernel. Be very careful when attempting this. You can optimize your system,
1421 but you can also cause it to crash. Never alter kernel parameters on a
1422 production system. Set up a development machine and test to make sure that
1423 everything works the way you want it to. You may have no alternative but to
1424 reboot the machine once an error has been made.
1426 To change a value, simply echo the new value into the file. An example is
1427 given below in the section on the file system data. You need to be root to do
1428 this. You can create your own boot script to perform this every time your
1429 system boots.
1431 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1432 general things in the operation of the Linux kernel. Since some of the files
1433 can inadvertently disrupt your system, it is advisable to read both
1434 documentation and source before actually making adjustments. In any case, be
1435 very careful when writing to any of these files. The entries in /proc may
1436 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1437 review the kernel documentation in the directory /usr/src/linux/Documentation.
1438 This chapter is heavily based on the documentation included in the pre 2.2
1439 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1441 Please see: Documentation/sysctl/ directory for descriptions of these
1442 entries.
1444 ------------------------------------------------------------------------------
1445 Summary
1446 ------------------------------------------------------------------------------
1447 Certain aspects of kernel behavior can be modified at runtime, without the
1448 need to recompile the kernel, or even to reboot the system. The files in the
1449 /proc/sys tree can not only be read, but also modified. You can use the echo
1450 command to write value into these files, thereby changing the default settings
1451 of the kernel.
1452 ------------------------------------------------------------------------------
1454 ------------------------------------------------------------------------------
1455 CHAPTER 3: PER-PROCESS PARAMETERS
1456 ------------------------------------------------------------------------------
1458 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1459 --------------------------------------------------------------------------------
1461 These file can be used to adjust the badness heuristic used to select which
1462 process gets killed in out of memory conditions.
1464 The badness heuristic assigns a value to each candidate task ranging from 0
1465 (never kill) to 1000 (always kill) to determine which process is targeted. The
1466 units are roughly a proportion along that range of allowed memory the process
1467 may allocate from based on an estimation of its current memory and swap use.
1468 For example, if a task is using all allowed memory, its badness score will be
1469 1000. If it is using half of its allowed memory, its score will be 500.
1471 There is an additional factor included in the badness score: the current memory
1472 and swap usage is discounted by 3% for root processes.
1474 The amount of "allowed" memory depends on the context in which the oom killer
1475 was called. If it is due to the memory assigned to the allocating task's cpuset
1476 being exhausted, the allowed memory represents the set of mems assigned to that
1477 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1478 memory represents the set of mempolicy nodes. If it is due to a memory
1479 limit (or swap limit) being reached, the allowed memory is that configured
1480 limit. Finally, if it is due to the entire system being out of memory, the
1481 allowed memory represents all allocatable resources.
1483 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1484 is used to determine which task to kill. Acceptable values range from -1000
1485 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1486 polarize the preference for oom killing either by always preferring a certain
1487 task or completely disabling it. The lowest possible value, -1000, is
1488 equivalent to disabling oom killing entirely for that task since it will always
1489 report a badness score of 0.
1491 Consequently, it is very simple for userspace to define the amount of memory to
1492 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1493 example, is roughly equivalent to allowing the remainder of tasks sharing the
1494 same system, cpuset, mempolicy, or memory controller resources to use at least
1495 50% more memory. A value of -500, on the other hand, would be roughly
1496 equivalent to discounting 50% of the task's allowed memory from being considered
1497 as scoring against the task.
1499 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1500 be used to tune the badness score. Its acceptable values range from -16
1501 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1502 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1503 scaled linearly with /proc/<pid>/oom_score_adj.
1505 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1506 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1507 requires CAP_SYS_RESOURCE.
1509 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1510 generation children with separate address spaces instead, if possible. This
1511 avoids servers and important system daemons from being killed and loses the
1512 minimal amount of work.
1515 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1516 -------------------------------------------------------------
1518 This file can be used to check the current score used by the oom-killer is for
1519 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1520 process should be killed in an out-of-memory situation.
1523 3.3 /proc/<pid>/io - Display the IO accounting fields
1524 -------------------------------------------------------
1526 This file contains IO statistics for each running process
1528 Example
1529 -------
1531 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1532 [1] 3828
1534 test:/tmp # cat /proc/3828/io
1535 rchar: 323934931
1536 wchar: 323929600
1537 syscr: 632687
1538 syscw: 632675
1539 read_bytes: 0
1540 write_bytes: 323932160
1541 cancelled_write_bytes: 0
1544 Description
1545 -----------
1547 rchar
1548 -----
1550 I/O counter: chars read
1551 The number of bytes which this task has caused to be read from storage. This
1552 is simply the sum of bytes which this process passed to read() and pread().
1553 It includes things like tty IO and it is unaffected by whether or not actual
1554 physical disk IO was required (the read might have been satisfied from
1555 pagecache)
1558 wchar
1559 -----
1561 I/O counter: chars written
1562 The number of bytes which this task has caused, or shall cause to be written
1563 to disk. Similar caveats apply here as with rchar.
1566 syscr
1567 -----
1569 I/O counter: read syscalls
1570 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1571 and pread().
1574 syscw
1575 -----
1577 I/O counter: write syscalls
1578 Attempt to count the number of write I/O operations, i.e. syscalls like
1579 write() and pwrite().
1582 read_bytes
1583 ----------
1585 I/O counter: bytes read
1586 Attempt to count the number of bytes which this process really did cause to
1587 be fetched from the storage layer. Done at the submit_bio() level, so it is
1588 accurate for block-backed filesystems. <please add status regarding NFS and
1589 CIFS at a later time>
1592 write_bytes
1593 -----------
1595 I/O counter: bytes written
1596 Attempt to count the number of bytes which this process caused to be sent to
1597 the storage layer. This is done at page-dirtying time.
1600 cancelled_write_bytes
1601 ---------------------
1603 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1604 then deletes the file, it will in fact perform no writeout. But it will have
1605 been accounted as having caused 1MB of write.
1606 In other words: The number of bytes which this process caused to not happen,
1607 by truncating pagecache. A task can cause "negative" IO too. If this task
1608 truncates some dirty pagecache, some IO which another task has been accounted
1609 for (in its write_bytes) will not be happening. We _could_ just subtract that
1610 from the truncating task's write_bytes, but there is information loss in doing
1611 that.
1614 Note
1615 ----
1617 At its current implementation state, this is a bit racy on 32-bit machines: if
1618 process A reads process B's /proc/pid/io while process B is updating one of
1619 those 64-bit counters, process A could see an intermediate result.
1622 More information about this can be found within the taskstats documentation in
1623 Documentation/accounting.
1625 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1626 ---------------------------------------------------------------
1627 When a process is dumped, all anonymous memory is written to a core file as
1628 long as the size of the core file isn't limited. But sometimes we don't want
1629 to dump some memory segments, for example, huge shared memory or DAX.
1630 Conversely, sometimes we want to save file-backed memory segments into a core
1631 file, not only the individual files.
1633 /proc/<pid>/coredump_filter allows you to customize which memory segments
1634 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1635 of memory types. If a bit of the bitmask is set, memory segments of the
1636 corresponding memory type are dumped, otherwise they are not dumped.
1638 The following 9 memory types are supported:
1639 - (bit 0) anonymous private memory
1640 - (bit 1) anonymous shared memory
1641 - (bit 2) file-backed private memory
1642 - (bit 3) file-backed shared memory
1643 - (bit 4) ELF header pages in file-backed private memory areas (it is
1644 effective only if the bit 2 is cleared)
1645 - (bit 5) hugetlb private memory
1646 - (bit 6) hugetlb shared memory
1647 - (bit 7) DAX private memory
1648 - (bit 8) DAX shared memory
1650 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1651 are always dumped regardless of the bitmask status.
1653 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1654 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1656 The default value of coredump_filter is 0x33; this means all anonymous memory
1657 segments, ELF header pages and hugetlb private memory are dumped.
1659 If you don't want to dump all shared memory segments attached to pid 1234,
1660 write 0x31 to the process's proc file.
1662 $ echo 0x31 > /proc/1234/coredump_filter
1664 When a new process is created, the process inherits the bitmask status from its
1665 parent. It is useful to set up coredump_filter before the program runs.
1666 For example:
1668 $ echo 0x7 > /proc/self/coredump_filter
1669 $ ./some_program
1671 3.5 /proc/<pid>/mountinfo - Information about mounts
1672 --------------------------------------------------------
1674 This file contains lines of the form:
1676 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1677 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1679 (1) mount ID: unique identifier of the mount (may be reused after umount)
1680 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1681 (3) major:minor: value of st_dev for files on filesystem
1682 (4) root: root of the mount within the filesystem
1683 (5) mount point: mount point relative to the process's root
1684 (6) mount options: per mount options
1685 (7) optional fields: zero or more fields of the form "tag[:value]"
1686 (8) separator: marks the end of the optional fields
1687 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1688 (10) mount source: filesystem specific information or "none"
1689 (11) super options: per super block options
1691 Parsers should ignore all unrecognised optional fields. Currently the
1692 possible optional fields are:
1694 shared:X mount is shared in peer group X
1695 master:X mount is slave to peer group X
1696 propagate_from:X mount is slave and receives propagation from peer group X (*)
1697 unbindable mount is unbindable
1699 (*) X is the closest dominant peer group under the process's root. If
1700 X is the immediate master of the mount, or if there's no dominant peer
1701 group under the same root, then only the "master:X" field is present
1702 and not the "propagate_from:X" field.
1704 For more information on mount propagation see:
1706 Documentation/filesystems/sharedsubtree.txt
1709 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1710 --------------------------------------------------------
1711 These files provide a method to access a tasks comm value. It also allows for
1712 a task to set its own or one of its thread siblings comm value. The comm value
1713 is limited in size compared to the cmdline value, so writing anything longer
1714 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1715 comm value.
1718 3.7 /proc/<pid>/task/<tid>/children - Information about task children
1719 -------------------------------------------------------------------------
1720 This file provides a fast way to retrieve first level children pids
1721 of a task pointed by <pid>/<tid> pair. The format is a space separated
1722 stream of pids.
1724 Note the "first level" here -- if a child has own children they will
1725 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1726 to obtain the descendants.
1728 Since this interface is intended to be fast and cheap it doesn't
1729 guarantee to provide precise results and some children might be
1730 skipped, especially if they've exited right after we printed their
1731 pids, so one need to either stop or freeze processes being inspected
1732 if precise results are needed.
1735 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1736 ---------------------------------------------------------------
1737 This file provides information associated with an opened file. The regular
1738 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1739 represents the current offset of the opened file in decimal form [see lseek(2)
1740 for details], 'flags' denotes the octal O_xxx mask the file has been
1741 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1742 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1743 for details].
1745 A typical output is
1747 pos: 0
1748 flags: 0100002
1749 mnt_id: 19
1751 All locks associated with a file descriptor are shown in its fdinfo too.
1753 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1755 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1756 pair provide additional information particular to the objects they represent.
1758 Eventfd files
1759 ~~~~~~~~~~~~~
1760 pos: 0
1761 flags: 04002
1762 mnt_id: 9
1763 eventfd-count: 5a
1765 where 'eventfd-count' is hex value of a counter.
1767 Signalfd files
1768 ~~~~~~~~~~~~~~
1769 pos: 0
1770 flags: 04002
1771 mnt_id: 9
1772 sigmask: 0000000000000200
1774 where 'sigmask' is hex value of the signal mask associated
1775 with a file.
1777 Epoll files
1778 ~~~~~~~~~~~
1779 pos: 0
1780 flags: 02
1781 mnt_id: 9
1782 tfd: 5 events: 1d data: ffffffffffffffff
1784 where 'tfd' is a target file descriptor number in decimal form,
1785 'events' is events mask being watched and the 'data' is data
1786 associated with a target [see epoll(7) for more details].
1788 Fsnotify files
1789 ~~~~~~~~~~~~~~
1790 For inotify files the format is the following
1792 pos: 0
1793 flags: 02000000
1794 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1796 where 'wd' is a watch descriptor in decimal form, ie a target file
1797 descriptor number, 'ino' and 'sdev' are inode and device where the
1798 target file resides and the 'mask' is the mask of events, all in hex
1799 form [see inotify(7) for more details].
1801 If the kernel was built with exportfs support, the path to the target
1802 file is encoded as a file handle. The file handle is provided by three
1803 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1804 format.
1806 If the kernel is built without exportfs support the file handle won't be
1807 printed out.
1809 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1811 For fanotify files the format is
1813 pos: 0
1814 flags: 02
1815 mnt_id: 9
1816 fanotify flags:10 event-flags:0
1817 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1818 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1820 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1821 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1822 flags associated with mark which are tracked separately from events
1823 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1824 mask and 'ignored_mask' is the mask of events which are to be ignored.
1825 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1826 does provide information about flags and mask used in fanotify_mark
1827 call [see fsnotify manpage for details].
1829 While the first three lines are mandatory and always printed, the rest is
1830 optional and may be omitted if no marks created yet.
1832 Timerfd files
1833 ~~~~~~~~~~~~~
1835 pos: 0
1836 flags: 02
1837 mnt_id: 9
1838 clockid: 0
1839 ticks: 0
1840 settime flags: 01
1841 it_value: (0, 49406829)
1842 it_interval: (1, 0)
1844 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1845 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1846 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1847 details]. 'it_value' is remaining time until the timer exiration.
1848 'it_interval' is the interval for the timer. Note the timer might be set up
1849 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1850 still exhibits timer's remaining time.
1852 3.9 /proc/<pid>/map_files - Information about memory mapped files
1853 ---------------------------------------------------------------------
1854 This directory contains symbolic links which represent memory mapped files
1855 the process is maintaining. Example output:
1857 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1858 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1859 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1860 | ...
1861 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1862 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1864 The name of a link represents the virtual memory bounds of a mapping, i.e.
1865 vm_area_struct::vm_start-vm_area_struct::vm_end.
1867 The main purpose of the map_files is to retrieve a set of memory mapped
1868 files in a fast way instead of parsing /proc/<pid>/maps or
1869 /proc/<pid>/smaps, both of which contain many more records. At the same
1870 time one can open(2) mappings from the listings of two processes and
1871 comparing their inode numbers to figure out which anonymous memory areas
1872 are actually shared.
1874 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
1875 ---------------------------------------------------------
1876 This file provides the value of the task's timerslack value in nanoseconds.
1877 This value specifies a amount of time that normal timers may be deferred
1878 in order to coalesce timers and avoid unnecessary wakeups.
1880 This allows a task's interactivity vs power consumption trade off to be
1881 adjusted.
1883 Writing 0 to the file will set the tasks timerslack to the default value.
1885 Valid values are from 0 - ULLONG_MAX
1887 An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1888 permissions on the task specified to change its timerslack_ns value.
1891 ------------------------------------------------------------------------------
1892 Configuring procfs
1893 ------------------------------------------------------------------------------
1895 4.1 Mount options
1896 ---------------------
1898 The following mount options are supported:
1900 hidepid= Set /proc/<pid>/ access mode.
1901 gid= Set the group authorized to learn processes information.
1903 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1904 (default).
1906 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1907 own. Sensitive files like cmdline, sched*, status are now protected against
1908 other users. This makes it impossible to learn whether any user runs
1909 specific program (given the program doesn't reveal itself by its behaviour).
1910 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1911 poorly written programs passing sensitive information via program arguments are
1912 now protected against local eavesdroppers.
1914 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1915 users. It doesn't mean that it hides a fact whether a process with a specific
1916 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1917 but it hides process' uid and gid, which may be learned by stat()'ing
1918 /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1919 information about running processes, whether some daemon runs with elevated
1920 privileges, whether other user runs some sensitive program, whether other users
1921 run any program at all, etc.
1923 gid= defines a group authorized to learn processes information otherwise
1924 prohibited by hidepid=. If you use some daemon like identd which needs to learn
1925 information about processes information, just add identd to this group.