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1 ------------------------------------------------------------------------------
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
47 4 Configuring procfs
48 4.1 Mount options
50 ------------------------------------------------------------------------------
51 Preface
52 ------------------------------------------------------------------------------
54 0.1 Introduction/Credits
55 ------------------------
57 This documentation is part of a soon (or so we hope) to be released book on
58 the SuSE Linux distribution. As there is no complete documentation for the
59 /proc file system and we've used many freely available sources to write these
60 chapters, it seems only fair to give the work back to the Linux community.
61 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
62 afraid it's still far from complete, but we hope it will be useful. As far as
63 we know, it is the first 'all-in-one' document about the /proc file system. It
64 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
65 SPARC, AXP, etc., features, you probably won't find what you are looking for.
66 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
67 additions and patches are welcome and will be added to this document if you
68 mail them to Bodo.
70 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
71 other people for help compiling this documentation. We'd also like to extend a
72 special thank you to Andi Kleen for documentation, which we relied on heavily
73 to create this document, as well as the additional information he provided.
74 Thanks to everybody else who contributed source or docs to the Linux kernel
75 and helped create a great piece of software... :)
77 If you have any comments, corrections or additions, please don't hesitate to
78 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
79 document.
81 The latest version of this document is available online at
82 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
84 If the above direction does not works for you, you could try the kernel
85 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
86 comandante@zaralinux.com.
88 0.2 Legal Stuff
89 ---------------
91 We don't guarantee the correctness of this document, and if you come to us
92 complaining about how you screwed up your system because of incorrect
93 documentation, we won't feel responsible...
95 ------------------------------------------------------------------------------
96 CHAPTER 1: COLLECTING SYSTEM INFORMATION
97 ------------------------------------------------------------------------------
99 ------------------------------------------------------------------------------
100 In This Chapter
101 ------------------------------------------------------------------------------
102 * Investigating the properties of the pseudo file system /proc and its
103 ability to provide information on the running Linux system
104 * Examining /proc's structure
105 * Uncovering various information about the kernel and the processes running
106 on the system
107 ------------------------------------------------------------------------------
110 The proc file system acts as an interface to internal data structures in the
111 kernel. It can be used to obtain information about the system and to change
112 certain kernel parameters at runtime (sysctl).
114 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
115 show you how you can use /proc/sys to change settings.
117 1.1 Process-Specific Subdirectories
118 -----------------------------------
120 The directory /proc contains (among other things) one subdirectory for each
121 process running on the system, which is named after the process ID (PID).
123 The link self points to the process reading the file system. Each process
124 subdirectory has the entries listed in Table 1-1.
127 Table 1-1: Process specific entries in /proc
128 ..............................................................................
129 File Content
130 clear_refs Clears page referenced bits shown in smaps output
131 cmdline Command line arguments
132 cpu Current and last cpu in which it was executed (2.4)(smp)
133 cwd Link to the current working directory
134 environ Values of environment variables
135 exe Link to the executable of this process
136 fd Directory, which contains all file descriptors
137 maps Memory maps to executables and library files (2.4)
138 mem Memory held by this process
139 root Link to the root directory of this process
140 stat Process status
141 statm Process memory status information
142 status Process status in human readable form
143 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
144 symbol the task is blocked in - or "0" if not blocked.
145 pagemap Page table
146 stack Report full stack trace, enable via CONFIG_STACKTRACE
147 smaps a extension based on maps, showing the memory consumption of
148 each mapping and flags associated with it
149 numa_maps an extension based on maps, showing the memory locality and
150 binding policy as well as mem usage (in pages) of each mapping.
151 ..............................................................................
153 For example, to get the status information of a process, all you have to do is
154 read the file /proc/PID/status:
156 >cat /proc/self/status
157 Name: cat
158 State: R (running)
159 Tgid: 5452
160 Pid: 5452
161 PPid: 743
162 TracerPid: 0 (2.4)
163 Uid: 501 501 501 501
164 Gid: 100 100 100 100
165 FDSize: 256
166 Groups: 100 14 16
167 VmPeak: 5004 kB
168 VmSize: 5004 kB
169 VmLck: 0 kB
170 VmHWM: 476 kB
171 VmRSS: 476 kB
172 VmData: 156 kB
173 VmStk: 88 kB
174 VmExe: 68 kB
175 VmLib: 1412 kB
176 VmPTE: 20 kb
177 VmSwap: 0 kB
178 HugetlbPages: 0 kB
179 Threads: 1
180 SigQ: 0/28578
181 SigPnd: 0000000000000000
182 ShdPnd: 0000000000000000
183 SigBlk: 0000000000000000
184 SigIgn: 0000000000000000
185 SigCgt: 0000000000000000
186 CapInh: 00000000fffffeff
187 CapPrm: 0000000000000000
188 CapEff: 0000000000000000
189 CapBnd: ffffffffffffffff
190 Seccomp: 0
191 voluntary_ctxt_switches: 0
192 nonvoluntary_ctxt_switches: 1
194 This shows you nearly the same information you would get if you viewed it with
195 the ps command. In fact, ps uses the proc file system to obtain its
196 information. But you get a more detailed view of the process by reading the
197 file /proc/PID/status. It fields are described in table 1-2.
199 The statm file contains more detailed information about the process
200 memory usage. Its seven fields are explained in Table 1-3. The stat file
201 contains details information about the process itself. Its fields are
202 explained in Table 1-4.
204 (for SMP CONFIG users)
205 For making accounting scalable, RSS related information are handled in an
206 asynchronous manner and the value may not be very precise. To see a precise
207 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
208 It's slow but very precise.
210 Table 1-2: Contents of the status files (as of 4.1)
211 ..............................................................................
212 Field Content
213 Name filename of the executable
214 State state (R is running, S is sleeping, D is sleeping
215 in an uninterruptible wait, Z is zombie,
216 T is traced or stopped)
217 Tgid thread group ID
218 Ngid NUMA group ID (0 if none)
219 Pid process id
220 PPid process id of the parent process
221 TracerPid PID of process tracing this process (0 if not)
222 Uid Real, effective, saved set, and file system UIDs
223 Gid Real, effective, saved set, and file system GIDs
224 FDSize number of file descriptor slots currently allocated
225 Groups supplementary group list
226 NStgid descendant namespace thread group ID hierarchy
227 NSpid descendant namespace process ID hierarchy
228 NSpgid descendant namespace process group ID hierarchy
229 NSsid descendant namespace session ID hierarchy
230 VmPeak peak virtual memory size
231 VmSize total program size
232 VmLck locked memory size
233 VmHWM peak resident set size ("high water mark")
234 VmRSS size of memory portions
235 VmData size of data, stack, and text segments
236 VmStk size of data, stack, and text segments
237 VmExe size of text segment
238 VmLib size of shared library code
239 VmPTE size of page table entries
240 VmPMD size of second level page tables
241 VmSwap size of swap usage (the number of referred swapents)
242 HugetlbPages size of hugetlb memory portions
243 Threads number of threads
244 SigQ number of signals queued/max. number for queue
245 SigPnd bitmap of pending signals for the thread
246 ShdPnd bitmap of shared pending signals for the process
247 SigBlk bitmap of blocked signals
248 SigIgn bitmap of ignored signals
249 SigCgt bitmap of caught signals
250 CapInh bitmap of inheritable capabilities
251 CapPrm bitmap of permitted capabilities
252 CapEff bitmap of effective capabilities
253 CapBnd bitmap of capabilities bounding set
254 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
255 Cpus_allowed mask of CPUs on which this process may run
256 Cpus_allowed_list Same as previous, but in "list format"
257 Mems_allowed mask of memory nodes allowed to this process
258 Mems_allowed_list Same as previous, but in "list format"
259 voluntary_ctxt_switches number of voluntary context switches
260 nonvoluntary_ctxt_switches number of non voluntary context switches
261 ..............................................................................
263 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
264 ..............................................................................
265 Field Content
266 size total program size (pages) (same as VmSize in status)
267 resident size of memory portions (pages) (same as VmRSS in status)
268 shared number of pages that are shared (i.e. backed by a file)
269 trs number of pages that are 'code' (not including libs; broken,
270 includes data segment)
271 lrs number of pages of library (always 0 on 2.6)
272 drs number of pages of data/stack (including libs; broken,
273 includes library text)
274 dt number of dirty pages (always 0 on 2.6)
275 ..............................................................................
278 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
279 ..............................................................................
280 Field Content
281 pid process id
282 tcomm filename of the executable
283 state state (R is running, S is sleeping, D is sleeping in an
284 uninterruptible wait, Z is zombie, T is traced or stopped)
285 ppid process id of the parent process
286 pgrp pgrp of the process
287 sid session id
288 tty_nr tty the process uses
289 tty_pgrp pgrp of the tty
290 flags task flags
291 min_flt number of minor faults
292 cmin_flt number of minor faults with child's
293 maj_flt number of major faults
294 cmaj_flt number of major faults with child's
295 utime user mode jiffies
296 stime kernel mode jiffies
297 cutime user mode jiffies with child's
298 cstime kernel mode jiffies with child's
299 priority priority level
300 nice nice level
301 num_threads number of threads
302 it_real_value (obsolete, always 0)
303 start_time time the process started after system boot
304 vsize virtual memory size
305 rss resident set memory size
306 rsslim current limit in bytes on the rss
307 start_code address above which program text can run
308 end_code address below which program text can run
309 start_stack address of the start of the main process stack
310 esp current value of ESP
311 eip current value of EIP
312 pending bitmap of pending signals
313 blocked bitmap of blocked signals
314 sigign bitmap of ignored signals
315 sigcatch bitmap of caught signals
316 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
317 0 (place holder)
318 0 (place holder)
319 exit_signal signal to send to parent thread on exit
320 task_cpu which CPU the task is scheduled on
321 rt_priority realtime priority
322 policy scheduling policy (man sched_setscheduler)
323 blkio_ticks time spent waiting for block IO
324 gtime guest time of the task in jiffies
325 cgtime guest time of the task children in jiffies
326 start_data address above which program data+bss is placed
327 end_data address below which program data+bss is placed
328 start_brk address above which program heap can be expanded with brk()
329 arg_start address above which program command line is placed
330 arg_end address below which program command line is placed
331 env_start address above which program environment is placed
332 env_end address below which program environment is placed
333 exit_code the thread's exit_code in the form reported by the waitpid system call
334 ..............................................................................
336 The /proc/PID/maps file containing the currently mapped memory regions and
337 their access permissions.
339 The format is:
341 address perms offset dev inode pathname
343 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
344 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
345 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
346 a7cb1000-a7cb2000 ---p 00000000 00:00 0
347 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
348 a7eb2000-a7eb3000 ---p 00000000 00:00 0
349 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
350 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
351 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
352 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
353 a800b000-a800e000 rw-p 00000000 00:00 0
354 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
355 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
356 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
357 a8024000-a8027000 rw-p 00000000 00:00 0
358 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
359 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
360 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
361 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
362 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
364 where "address" is the address space in the process that it occupies, "perms"
365 is a set of permissions:
367 r = read
368 w = write
369 x = execute
370 s = shared
371 p = private (copy on write)
373 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
374 "inode" is the inode on that device. 0 indicates that no inode is associated
375 with the memory region, as the case would be with BSS (uninitialized data).
376 The "pathname" shows the name associated file for this mapping. If the mapping
377 is not associated with a file:
379 [heap] = the heap of the program
380 [stack] = the stack of the main process
381 [vdso] = the "virtual dynamic shared object",
382 the kernel system call handler
384 or if empty, the mapping is anonymous.
386 The /proc/PID/smaps is an extension based on maps, showing the memory
387 consumption for each of the process's mappings. For each of mappings there
388 is a series of lines such as the following:
390 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
391 Size: 1084 kB
392 Rss: 892 kB
393 Pss: 374 kB
394 Shared_Clean: 892 kB
395 Shared_Dirty: 0 kB
396 Private_Clean: 0 kB
397 Private_Dirty: 0 kB
398 Referenced: 892 kB
399 Anonymous: 0 kB
400 AnonHugePages: 0 kB
401 Shared_Hugetlb: 0 kB
402 Private_Hugetlb: 0 kB
403 Swap: 0 kB
404 SwapPss: 0 kB
405 KernelPageSize: 4 kB
406 MMUPageSize: 4 kB
407 Locked: 0 kB
408 VmFlags: rd ex mr mw me dw
410 the first of these lines shows the same information as is displayed for the
411 mapping in /proc/PID/maps. The remaining lines show the size of the mapping
412 (size), the amount of the mapping that is currently resident in RAM (RSS), the
413 process' proportional share of this mapping (PSS), the number of clean and
414 dirty private pages in the mapping.
416 The "proportional set size" (PSS) of a process is the count of pages it has
417 in memory, where each page is divided by the number of processes sharing it.
418 So if a process has 1000 pages all to itself, and 1000 shared with one other
419 process, its PSS will be 1500.
420 Note that even a page which is part of a MAP_SHARED mapping, but has only
421 a single pte mapped, i.e. is currently used by only one process, is accounted
422 as private and not as shared.
423 "Referenced" indicates the amount of memory currently marked as referenced or
424 accessed.
425 "Anonymous" shows the amount of memory that does not belong to any file. Even
426 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
427 and a page is modified, the file page is replaced by a private anonymous copy.
428 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
429 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
430 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
431 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
432 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
433 "SwapPss" shows proportional swap share of this mapping.
434 "Locked" indicates whether the mapping is locked in memory or not.
436 "VmFlags" field deserves a separate description. This member represents the kernel
437 flags associated with the particular virtual memory area in two letter encoded
438 manner. The codes are the following:
439 rd - readable
440 wr - writeable
441 ex - executable
442 sh - shared
443 mr - may read
444 mw - may write
445 me - may execute
446 ms - may share
447 gd - stack segment growns down
448 pf - pure PFN range
449 dw - disabled write to the mapped file
450 lo - pages are locked in memory
451 io - memory mapped I/O area
452 sr - sequential read advise provided
453 rr - random read advise provided
454 dc - do not copy area on fork
455 de - do not expand area on remapping
456 ac - area is accountable
457 nr - swap space is not reserved for the area
458 ht - area uses huge tlb pages
459 ar - architecture specific flag
460 dd - do not include area into core dump
461 sd - soft-dirty flag
462 mm - mixed map area
463 hg - huge page advise flag
464 nh - no-huge page advise flag
465 mg - mergable advise flag
467 Note that there is no guarantee that every flag and associated mnemonic will
468 be present in all further kernel releases. Things get changed, the flags may
469 be vanished or the reverse -- new added.
471 This file is only present if the CONFIG_MMU kernel configuration option is
472 enabled.
474 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
475 bits on both physical and virtual pages associated with a process, and the
476 soft-dirty bit on pte (see Documentation/vm/soft-dirty.txt for details).
477 To clear the bits for all the pages associated with the process
478 > echo 1 > /proc/PID/clear_refs
480 To clear the bits for the anonymous pages associated with the process
481 > echo 2 > /proc/PID/clear_refs
483 To clear the bits for the file mapped pages associated with the process
484 > echo 3 > /proc/PID/clear_refs
486 To clear the soft-dirty bit
487 > echo 4 > /proc/PID/clear_refs
489 To reset the peak resident set size ("high water mark") to the process's
490 current value:
491 > echo 5 > /proc/PID/clear_refs
493 Any other value written to /proc/PID/clear_refs will have no effect.
495 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
496 using /proc/kpageflags and number of times a page is mapped using
497 /proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.
499 The /proc/pid/numa_maps is an extension based on maps, showing the memory
500 locality and binding policy, as well as the memory usage (in pages) of
501 each mapping. The output follows a general format where mapping details get
502 summarized separated by blank spaces, one mapping per each file line:
504 address policy mapping details
506 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
507 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
508 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
509 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
510 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
511 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
512 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
513 320698b000 default file=/lib64/libc-2.12.so
514 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
515 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
516 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
517 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
518 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
519 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
520 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
521 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
523 Where:
524 "address" is the starting address for the mapping;
525 "policy" reports the NUMA memory policy set for the mapping (see vm/numa_memory_policy.txt);
526 "mapping details" summarizes mapping data such as mapping type, page usage counters,
527 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
528 size, in KB, that is backing the mapping up.
530 1.2 Kernel data
531 ---------------
533 Similar to the process entries, the kernel data files give information about
534 the running kernel. The files used to obtain this information are contained in
535 /proc and are listed in Table 1-5. Not all of these will be present in your
536 system. It depends on the kernel configuration and the loaded modules, which
537 files are there, and which are missing.
539 Table 1-5: Kernel info in /proc
540 ..............................................................................
541 File Content
542 apm Advanced power management info
543 buddyinfo Kernel memory allocator information (see text) (2.5)
544 bus Directory containing bus specific information
545 cmdline Kernel command line
546 cpuinfo Info about the CPU
547 devices Available devices (block and character)
548 dma Used DMS channels
549 filesystems Supported filesystems
550 driver Various drivers grouped here, currently rtc (2.4)
551 execdomains Execdomains, related to security (2.4)
552 fb Frame Buffer devices (2.4)
553 fs File system parameters, currently nfs/exports (2.4)
554 ide Directory containing info about the IDE subsystem
555 interrupts Interrupt usage
556 iomem Memory map (2.4)
557 ioports I/O port usage
558 irq Masks for irq to cpu affinity (2.4)(smp?)
559 isapnp ISA PnP (Plug&Play) Info (2.4)
560 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
561 kmsg Kernel messages
562 ksyms Kernel symbol table
563 loadavg Load average of last 1, 5 & 15 minutes
564 locks Kernel locks
565 meminfo Memory info
566 misc Miscellaneous
567 modules List of loaded modules
568 mounts Mounted filesystems
569 net Networking info (see text)
570 pagetypeinfo Additional page allocator information (see text) (2.5)
571 partitions Table of partitions known to the system
572 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
573 decoupled by lspci (2.4)
574 rtc Real time clock
575 scsi SCSI info (see text)
576 slabinfo Slab pool info
577 softirqs softirq usage
578 stat Overall statistics
579 swaps Swap space utilization
580 sys See chapter 2
581 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
582 tty Info of tty drivers
583 uptime Wall clock since boot, combined idle time of all cpus
584 version Kernel version
585 video bttv info of video resources (2.4)
586 vmallocinfo Show vmalloced areas
587 ..............................................................................
589 You can, for example, check which interrupts are currently in use and what
590 they are used for by looking in the file /proc/interrupts:
592 > cat /proc/interrupts
593 CPU0
594 0: 8728810 XT-PIC timer
595 1: 895 XT-PIC keyboard
596 2: 0 XT-PIC cascade
597 3: 531695 XT-PIC aha152x
598 4: 2014133 XT-PIC serial
599 5: 44401 XT-PIC pcnet_cs
600 8: 2 XT-PIC rtc
601 11: 8 XT-PIC i82365
602 12: 182918 XT-PIC PS/2 Mouse
603 13: 1 XT-PIC fpu
604 14: 1232265 XT-PIC ide0
605 15: 7 XT-PIC ide1
606 NMI: 0
608 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
609 output of a SMP machine):
611 > cat /proc/interrupts
613 CPU0 CPU1
614 0: 1243498 1214548 IO-APIC-edge timer
615 1: 8949 8958 IO-APIC-edge keyboard
616 2: 0 0 XT-PIC cascade
617 5: 11286 10161 IO-APIC-edge soundblaster
618 8: 1 0 IO-APIC-edge rtc
619 9: 27422 27407 IO-APIC-edge 3c503
620 12: 113645 113873 IO-APIC-edge PS/2 Mouse
621 13: 0 0 XT-PIC fpu
622 14: 22491 24012 IO-APIC-edge ide0
623 15: 2183 2415 IO-APIC-edge ide1
624 17: 30564 30414 IO-APIC-level eth0
625 18: 177 164 IO-APIC-level bttv
626 NMI: 2457961 2457959
627 LOC: 2457882 2457881
628 ERR: 2155
630 NMI is incremented in this case because every timer interrupt generates a NMI
631 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
633 LOC is the local interrupt counter of the internal APIC of every CPU.
635 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
636 connects the CPUs in a SMP system. This means that an error has been detected,
637 the IO-APIC automatically retry the transmission, so it should not be a big
638 problem, but you should read the SMP-FAQ.
640 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
641 /proc/interrupts to display every IRQ vector in use by the system, not
642 just those considered 'most important'. The new vectors are:
644 THR -- interrupt raised when a machine check threshold counter
645 (typically counting ECC corrected errors of memory or cache) exceeds
646 a configurable threshold. Only available on some systems.
648 TRM -- a thermal event interrupt occurs when a temperature threshold
649 has been exceeded for the CPU. This interrupt may also be generated
650 when the temperature drops back to normal.
652 SPU -- a spurious interrupt is some interrupt that was raised then lowered
653 by some IO device before it could be fully processed by the APIC. Hence
654 the APIC sees the interrupt but does not know what device it came from.
655 For this case the APIC will generate the interrupt with a IRQ vector
656 of 0xff. This might also be generated by chipset bugs.
658 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
659 sent from one CPU to another per the needs of the OS. Typically,
660 their statistics are used by kernel developers and interested users to
661 determine the occurrence of interrupts of the given type.
663 The above IRQ vectors are displayed only when relevant. For example,
664 the threshold vector does not exist on x86_64 platforms. Others are
665 suppressed when the system is a uniprocessor. As of this writing, only
666 i386 and x86_64 platforms support the new IRQ vector displays.
668 Of some interest is the introduction of the /proc/irq directory to 2.4.
669 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
670 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
671 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
672 prof_cpu_mask.
674 For example
675 > ls /proc/irq/
676 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
677 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
678 > ls /proc/irq/0/
679 smp_affinity
681 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
682 IRQ, you can set it by doing:
684 > echo 1 > /proc/irq/10/smp_affinity
686 This means that only the first CPU will handle the IRQ, but you can also echo
687 5 which means that only the first and fourth CPU can handle the IRQ.
689 The contents of each smp_affinity file is the same by default:
691 > cat /proc/irq/0/smp_affinity
692 ffffffff
694 There is an alternate interface, smp_affinity_list which allows specifying
695 a cpu range instead of a bitmask:
697 > cat /proc/irq/0/smp_affinity_list
698 1024-1031
700 The default_smp_affinity mask applies to all non-active IRQs, which are the
701 IRQs which have not yet been allocated/activated, and hence which lack a
702 /proc/irq/[0-9]* directory.
704 The node file on an SMP system shows the node to which the device using the IRQ
705 reports itself as being attached. This hardware locality information does not
706 include information about any possible driver locality preference.
708 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
709 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
711 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
712 between all the CPUs which are allowed to handle it. As usual the kernel has
713 more info than you and does a better job than you, so the defaults are the
714 best choice for almost everyone. [Note this applies only to those IO-APIC's
715 that support "Round Robin" interrupt distribution.]
717 There are three more important subdirectories in /proc: net, scsi, and sys.
718 The general rule is that the contents, or even the existence of these
719 directories, depend on your kernel configuration. If SCSI is not enabled, the
720 directory scsi may not exist. The same is true with the net, which is there
721 only when networking support is present in the running kernel.
723 The slabinfo file gives information about memory usage at the slab level.
724 Linux uses slab pools for memory management above page level in version 2.2.
725 Commonly used objects have their own slab pool (such as network buffers,
726 directory cache, and so on).
728 ..............................................................................
730 > cat /proc/buddyinfo
732 Node 0, zone DMA 0 4 5 4 4 3 ...
733 Node 0, zone Normal 1 0 0 1 101 8 ...
734 Node 0, zone HighMem 2 0 0 1 1 0 ...
736 External fragmentation is a problem under some workloads, and buddyinfo is a
737 useful tool for helping diagnose these problems. Buddyinfo will give you a
738 clue as to how big an area you can safely allocate, or why a previous
739 allocation failed.
741 Each column represents the number of pages of a certain order which are
742 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
743 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
744 available in ZONE_NORMAL, etc...
746 More information relevant to external fragmentation can be found in
747 pagetypeinfo.
749 > cat /proc/pagetypeinfo
750 Page block order: 9
751 Pages per block: 512
753 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
754 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
755 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
756 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
757 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
758 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
759 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
760 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
761 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
762 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
763 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
765 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
766 Node 0, zone DMA 2 0 5 1 0
767 Node 0, zone DMA32 41 6 967 2 0
769 Fragmentation avoidance in the kernel works by grouping pages of different
770 migrate types into the same contiguous regions of memory called page blocks.
771 A page block is typically the size of the default hugepage size e.g. 2MB on
772 X86-64. By keeping pages grouped based on their ability to move, the kernel
773 can reclaim pages within a page block to satisfy a high-order allocation.
775 The pagetypinfo begins with information on the size of a page block. It
776 then gives the same type of information as buddyinfo except broken down
777 by migrate-type and finishes with details on how many page blocks of each
778 type exist.
780 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
781 from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
782 make an estimate of the likely number of huge pages that can be allocated
783 at a given point in time. All the "Movable" blocks should be allocatable
784 unless memory has been mlock()'d. Some of the Reclaimable blocks should
785 also be allocatable although a lot of filesystem metadata may have to be
786 reclaimed to achieve this.
788 ..............................................................................
790 meminfo:
792 Provides information about distribution and utilization of memory. This
793 varies by architecture and compile options. The following is from a
794 16GB PIII, which has highmem enabled. You may not have all of these fields.
796 > cat /proc/meminfo
798 MemTotal: 16344972 kB
799 MemFree: 13634064 kB
800 MemAvailable: 14836172 kB
801 Buffers: 3656 kB
802 Cached: 1195708 kB
803 SwapCached: 0 kB
804 Active: 891636 kB
805 Inactive: 1077224 kB
806 HighTotal: 15597528 kB
807 HighFree: 13629632 kB
808 LowTotal: 747444 kB
809 LowFree: 4432 kB
810 SwapTotal: 0 kB
811 SwapFree: 0 kB
812 Dirty: 968 kB
813 Writeback: 0 kB
814 AnonPages: 861800 kB
815 Mapped: 280372 kB
816 Slab: 284364 kB
817 SReclaimable: 159856 kB
818 SUnreclaim: 124508 kB
819 PageTables: 24448 kB
820 NFS_Unstable: 0 kB
821 Bounce: 0 kB
822 WritebackTmp: 0 kB
823 CommitLimit: 7669796 kB
824 Committed_AS: 100056 kB
825 VmallocTotal: 112216 kB
826 VmallocUsed: 428 kB
827 VmallocChunk: 111088 kB
828 AnonHugePages: 49152 kB
830 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
831 bits and the kernel binary code)
832 MemFree: The sum of LowFree+HighFree
833 MemAvailable: An estimate of how much memory is available for starting new
834 applications, without swapping. Calculated from MemFree,
835 SReclaimable, the size of the file LRU lists, and the low
836 watermarks in each zone.
837 The estimate takes into account that the system needs some
838 page cache to function well, and that not all reclaimable
839 slab will be reclaimable, due to items being in use. The
840 impact of those factors will vary from system to system.
841 Buffers: Relatively temporary storage for raw disk blocks
842 shouldn't get tremendously large (20MB or so)
843 Cached: in-memory cache for files read from the disk (the
844 pagecache). Doesn't include SwapCached
845 SwapCached: Memory that once was swapped out, is swapped back in but
846 still also is in the swapfile (if memory is needed it
847 doesn't need to be swapped out AGAIN because it is already
848 in the swapfile. This saves I/O)
849 Active: Memory that has been used more recently and usually not
850 reclaimed unless absolutely necessary.
851 Inactive: Memory which has been less recently used. It is more
852 eligible to be reclaimed for other purposes
853 HighTotal:
854 HighFree: Highmem is all memory above ~860MB of physical memory
855 Highmem areas are for use by userspace programs, or
856 for the pagecache. The kernel must use tricks to access
857 this memory, making it slower to access than lowmem.
858 LowTotal:
859 LowFree: Lowmem is memory which can be used for everything that
860 highmem can be used for, but it is also available for the
861 kernel's use for its own data structures. Among many
862 other things, it is where everything from the Slab is
863 allocated. Bad things happen when you're out of lowmem.
864 SwapTotal: total amount of swap space available
865 SwapFree: Memory which has been evicted from RAM, and is temporarily
866 on the disk
867 Dirty: Memory which is waiting to get written back to the disk
868 Writeback: Memory which is actively being written back to the disk
869 AnonPages: Non-file backed pages mapped into userspace page tables
870 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
871 Mapped: files which have been mmaped, such as libraries
872 Slab: in-kernel data structures cache
873 SReclaimable: Part of Slab, that might be reclaimed, such as caches
874 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
875 PageTables: amount of memory dedicated to the lowest level of page
876 tables.
877 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
878 storage
879 Bounce: Memory used for block device "bounce buffers"
880 WritebackTmp: Memory used by FUSE for temporary writeback buffers
881 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
882 this is the total amount of memory currently available to
883 be allocated on the system. This limit is only adhered to
884 if strict overcommit accounting is enabled (mode 2 in
885 'vm.overcommit_memory').
886 The CommitLimit is calculated with the following formula:
887 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
888 overcommit_ratio / 100 + [total swap pages]
889 For example, on a system with 1G of physical RAM and 7G
890 of swap with a `vm.overcommit_ratio` of 30 it would
891 yield a CommitLimit of 7.3G.
892 For more details, see the memory overcommit documentation
893 in vm/overcommit-accounting.
894 Committed_AS: The amount of memory presently allocated on the system.
895 The committed memory is a sum of all of the memory which
896 has been allocated by processes, even if it has not been
897 "used" by them as of yet. A process which malloc()'s 1G
898 of memory, but only touches 300M of it will show up as
899 using 1G. This 1G is memory which has been "committed" to
900 by the VM and can be used at any time by the allocating
901 application. With strict overcommit enabled on the system
902 (mode 2 in 'vm.overcommit_memory'),allocations which would
903 exceed the CommitLimit (detailed above) will not be permitted.
904 This is useful if one needs to guarantee that processes will
905 not fail due to lack of memory once that memory has been
906 successfully allocated.
907 VmallocTotal: total size of vmalloc memory area
908 VmallocUsed: amount of vmalloc area which is used
909 VmallocChunk: largest contiguous block of vmalloc area which is free
911 ..............................................................................
913 vmallocinfo:
915 Provides information about vmalloced/vmaped areas. One line per area,
916 containing the virtual address range of the area, size in bytes,
917 caller information of the creator, and optional information depending
918 on the kind of area :
920 pages=nr number of pages
921 phys=addr if a physical address was specified
922 ioremap I/O mapping (ioremap() and friends)
923 vmalloc vmalloc() area
924 vmap vmap()ed pages
925 user VM_USERMAP area
926 vpages buffer for pages pointers was vmalloced (huge area)
927 N<node>=nr (Only on NUMA kernels)
928 Number of pages allocated on memory node <node>
930 > cat /proc/vmallocinfo
931 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
932 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
933 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
934 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
935 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
936 phys=7fee8000 ioremap
937 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
938 phys=7fee7000 ioremap
939 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
940 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
941 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
942 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
943 pages=2 vmalloc N1=2
944 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
945 /0x130 [x_tables] pages=4 vmalloc N0=4
946 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
947 pages=14 vmalloc N2=14
948 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
949 pages=4 vmalloc N1=4
950 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
951 pages=2 vmalloc N1=2
952 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
953 pages=10 vmalloc N0=10
955 ..............................................................................
957 softirqs:
959 Provides counts of softirq handlers serviced since boot time, for each cpu.
961 > cat /proc/softirqs
962 CPU0 CPU1 CPU2 CPU3
963 HI: 0 0 0 0
964 TIMER: 27166 27120 27097 27034
965 NET_TX: 0 0 0 17
966 NET_RX: 42 0 0 39
967 BLOCK: 0 0 107 1121
968 TASKLET: 0 0 0 290
969 SCHED: 27035 26983 26971 26746
970 HRTIMER: 0 0 0 0
971 RCU: 1678 1769 2178 2250
974 1.3 IDE devices in /proc/ide
975 ----------------------------
977 The subdirectory /proc/ide contains information about all IDE devices of which
978 the kernel is aware. There is one subdirectory for each IDE controller, the
979 file drivers and a link for each IDE device, pointing to the device directory
980 in the controller specific subtree.
982 The file drivers contains general information about the drivers used for the
983 IDE devices:
985 > cat /proc/ide/drivers
986 ide-cdrom version 4.53
987 ide-disk version 1.08
989 More detailed information can be found in the controller specific
990 subdirectories. These are named ide0, ide1 and so on. Each of these
991 directories contains the files shown in table 1-6.
994 Table 1-6: IDE controller info in /proc/ide/ide?
995 ..............................................................................
996 File Content
997 channel IDE channel (0 or 1)
998 config Configuration (only for PCI/IDE bridge)
999 mate Mate name
1000 model Type/Chipset of IDE controller
1001 ..............................................................................
1003 Each device connected to a controller has a separate subdirectory in the
1004 controllers directory. The files listed in table 1-7 are contained in these
1005 directories.
1008 Table 1-7: IDE device information
1009 ..............................................................................
1010 File Content
1011 cache The cache
1012 capacity Capacity of the medium (in 512Byte blocks)
1013 driver driver and version
1014 geometry physical and logical geometry
1015 identify device identify block
1016 media media type
1017 model device identifier
1018 settings device setup
1019 smart_thresholds IDE disk management thresholds
1020 smart_values IDE disk management values
1021 ..............................................................................
1023 The most interesting file is settings. This file contains a nice overview of
1024 the drive parameters:
1026 # cat /proc/ide/ide0/hda/settings
1027 name value min max mode
1028 ---- ----- --- --- ----
1029 bios_cyl 526 0 65535 rw
1030 bios_head 255 0 255 rw
1031 bios_sect 63 0 63 rw
1032 breada_readahead 4 0 127 rw
1033 bswap 0 0 1 r
1034 file_readahead 72 0 2097151 rw
1035 io_32bit 0 0 3 rw
1036 keepsettings 0 0 1 rw
1037 max_kb_per_request 122 1 127 rw
1038 multcount 0 0 8 rw
1039 nice1 1 0 1 rw
1040 nowerr 0 0 1 rw
1041 pio_mode write-only 0 255 w
1042 slow 0 0 1 rw
1043 unmaskirq 0 0 1 rw
1044 using_dma 0 0 1 rw
1047 1.4 Networking info in /proc/net
1048 --------------------------------
1050 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1051 additional values you get for IP version 6 if you configure the kernel to
1052 support this. Table 1-9 lists the files and their meaning.
1055 Table 1-8: IPv6 info in /proc/net
1056 ..............................................................................
1057 File Content
1058 udp6 UDP sockets (IPv6)
1059 tcp6 TCP sockets (IPv6)
1060 raw6 Raw device statistics (IPv6)
1061 igmp6 IP multicast addresses, which this host joined (IPv6)
1062 if_inet6 List of IPv6 interface addresses
1063 ipv6_route Kernel routing table for IPv6
1064 rt6_stats Global IPv6 routing tables statistics
1065 sockstat6 Socket statistics (IPv6)
1066 snmp6 Snmp data (IPv6)
1067 ..............................................................................
1070 Table 1-9: Network info in /proc/net
1071 ..............................................................................
1072 File Content
1073 arp Kernel ARP table
1074 dev network devices with statistics
1075 dev_mcast the Layer2 multicast groups a device is listening too
1076 (interface index, label, number of references, number of bound
1077 addresses).
1078 dev_stat network device status
1079 ip_fwchains Firewall chain linkage
1080 ip_fwnames Firewall chain names
1081 ip_masq Directory containing the masquerading tables
1082 ip_masquerade Major masquerading table
1083 netstat Network statistics
1084 raw raw device statistics
1085 route Kernel routing table
1086 rpc Directory containing rpc info
1087 rt_cache Routing cache
1088 snmp SNMP data
1089 sockstat Socket statistics
1090 tcp TCP sockets
1091 udp UDP sockets
1092 unix UNIX domain sockets
1093 wireless Wireless interface data (Wavelan etc)
1094 igmp IP multicast addresses, which this host joined
1095 psched Global packet scheduler parameters.
1096 netlink List of PF_NETLINK sockets
1097 ip_mr_vifs List of multicast virtual interfaces
1098 ip_mr_cache List of multicast routing cache
1099 ..............................................................................
1101 You can use this information to see which network devices are available in
1102 your system and how much traffic was routed over those devices:
1104 > cat /proc/net/dev
1105 Inter-|Receive |[...
1106 face |bytes packets errs drop fifo frame compressed multicast|[...
1107 lo: 908188 5596 0 0 0 0 0 0 [...
1108 ppp0:15475140 20721 410 0 0 410 0 0 [...
1109 eth0: 614530 7085 0 0 0 0 0 1 [...
1111 ...] Transmit
1112 ...] bytes packets errs drop fifo colls carrier compressed
1113 ...] 908188 5596 0 0 0 0 0 0
1114 ...] 1375103 17405 0 0 0 0 0 0
1115 ...] 1703981 5535 0 0 0 3 0 0
1117 In addition, each Channel Bond interface has its own directory. For
1118 example, the bond0 device will have a directory called /proc/net/bond0/.
1119 It will contain information that is specific to that bond, such as the
1120 current slaves of the bond, the link status of the slaves, and how
1121 many times the slaves link has failed.
1123 1.5 SCSI info
1124 -------------
1126 If you have a SCSI host adapter in your system, you'll find a subdirectory
1127 named after the driver for this adapter in /proc/scsi. You'll also see a list
1128 of all recognized SCSI devices in /proc/scsi:
1130 >cat /proc/scsi/scsi
1131 Attached devices:
1132 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1133 Vendor: IBM Model: DGHS09U Rev: 03E0
1134 Type: Direct-Access ANSI SCSI revision: 03
1135 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1136 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1137 Type: CD-ROM ANSI SCSI revision: 02
1140 The directory named after the driver has one file for each adapter found in
1141 the system. These files contain information about the controller, including
1142 the used IRQ and the IO address range. The amount of information shown is
1143 dependent on the adapter you use. The example shows the output for an Adaptec
1144 AHA-2940 SCSI adapter:
1146 > cat /proc/scsi/aic7xxx/0
1148 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1149 Compile Options:
1150 TCQ Enabled By Default : Disabled
1151 AIC7XXX_PROC_STATS : Disabled
1152 AIC7XXX_RESET_DELAY : 5
1153 Adapter Configuration:
1154 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1155 Ultra Wide Controller
1156 PCI MMAPed I/O Base: 0xeb001000
1157 Adapter SEEPROM Config: SEEPROM found and used.
1158 Adaptec SCSI BIOS: Enabled
1159 IRQ: 10
1160 SCBs: Active 0, Max Active 2,
1161 Allocated 15, HW 16, Page 255
1162 Interrupts: 160328
1163 BIOS Control Word: 0x18b6
1164 Adapter Control Word: 0x005b
1165 Extended Translation: Enabled
1166 Disconnect Enable Flags: 0xffff
1167 Ultra Enable Flags: 0x0001
1168 Tag Queue Enable Flags: 0x0000
1169 Ordered Queue Tag Flags: 0x0000
1170 Default Tag Queue Depth: 8
1171 Tagged Queue By Device array for aic7xxx host instance 0:
1172 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1173 Actual queue depth per device for aic7xxx host instance 0:
1174 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1175 Statistics:
1176 (scsi0:0:0:0)
1177 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1178 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1179 Total transfers 160151 (74577 reads and 85574 writes)
1180 (scsi0:0:6:0)
1181 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1182 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1183 Total transfers 0 (0 reads and 0 writes)
1186 1.6 Parallel port info in /proc/parport
1187 ---------------------------------------
1189 The directory /proc/parport contains information about the parallel ports of
1190 your system. It has one subdirectory for each port, named after the port
1191 number (0,1,2,...).
1193 These directories contain the four files shown in Table 1-10.
1196 Table 1-10: Files in /proc/parport
1197 ..............................................................................
1198 File Content
1199 autoprobe Any IEEE-1284 device ID information that has been acquired.
1200 devices list of the device drivers using that port. A + will appear by the
1201 name of the device currently using the port (it might not appear
1202 against any).
1203 hardware Parallel port's base address, IRQ line and DMA channel.
1204 irq IRQ that parport is using for that port. This is in a separate
1205 file to allow you to alter it by writing a new value in (IRQ
1206 number or none).
1207 ..............................................................................
1209 1.7 TTY info in /proc/tty
1210 -------------------------
1212 Information about the available and actually used tty's can be found in the
1213 directory /proc/tty.You'll find entries for drivers and line disciplines in
1214 this directory, as shown in Table 1-11.
1217 Table 1-11: Files in /proc/tty
1218 ..............................................................................
1219 File Content
1220 drivers list of drivers and their usage
1221 ldiscs registered line disciplines
1222 driver/serial usage statistic and status of single tty lines
1223 ..............................................................................
1225 To see which tty's are currently in use, you can simply look into the file
1226 /proc/tty/drivers:
1228 > cat /proc/tty/drivers
1229 pty_slave /dev/pts 136 0-255 pty:slave
1230 pty_master /dev/ptm 128 0-255 pty:master
1231 pty_slave /dev/ttyp 3 0-255 pty:slave
1232 pty_master /dev/pty 2 0-255 pty:master
1233 serial /dev/cua 5 64-67 serial:callout
1234 serial /dev/ttyS 4 64-67 serial
1235 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1236 /dev/ptmx /dev/ptmx 5 2 system
1237 /dev/console /dev/console 5 1 system:console
1238 /dev/tty /dev/tty 5 0 system:/dev/tty
1239 unknown /dev/tty 4 1-63 console
1242 1.8 Miscellaneous kernel statistics in /proc/stat
1243 -------------------------------------------------
1245 Various pieces of information about kernel activity are available in the
1246 /proc/stat file. All of the numbers reported in this file are aggregates
1247 since the system first booted. For a quick look, simply cat the file:
1249 > cat /proc/stat
1250 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1251 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1252 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1253 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1254 ctxt 1990473
1255 btime 1062191376
1256 processes 2915
1257 procs_running 1
1258 procs_blocked 0
1259 softirq 183433 0 21755 12 39 1137 231 21459 2263
1261 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1262 lines. These numbers identify the amount of time the CPU has spent performing
1263 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1264 second). The meanings of the columns are as follows, from left to right:
1266 - user: normal processes executing in user mode
1267 - nice: niced processes executing in user mode
1268 - system: processes executing in kernel mode
1269 - idle: twiddling thumbs
1270 - iowait: waiting for I/O to complete
1271 - irq: servicing interrupts
1272 - softirq: servicing softirqs
1273 - steal: involuntary wait
1274 - guest: running a normal guest
1275 - guest_nice: running a niced guest
1277 The "intr" line gives counts of interrupts serviced since boot time, for each
1278 of the possible system interrupts. The first column is the total of all
1279 interrupts serviced including unnumbered architecture specific interrupts;
1280 each subsequent column is the total for that particular numbered interrupt.
1281 Unnumbered interrupts are not shown, only summed into the total.
1283 The "ctxt" line gives the total number of context switches across all CPUs.
1285 The "btime" line gives the time at which the system booted, in seconds since
1286 the Unix epoch.
1288 The "processes" line gives the number of processes and threads created, which
1289 includes (but is not limited to) those created by calls to the fork() and
1290 clone() system calls.
1292 The "procs_running" line gives the total number of threads that are
1293 running or ready to run (i.e., the total number of runnable threads).
1295 The "procs_blocked" line gives the number of processes currently blocked,
1296 waiting for I/O to complete.
1298 The "softirq" line gives counts of softirqs serviced since boot time, for each
1299 of the possible system softirqs. The first column is the total of all
1300 softirqs serviced; each subsequent column is the total for that particular
1301 softirq.
1304 1.9 Ext4 file system parameters
1305 -------------------------------
1307 Information about mounted ext4 file systems can be found in
1308 /proc/fs/ext4. Each mounted filesystem will have a directory in
1309 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1310 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1311 in Table 1-12, below.
1313 Table 1-12: Files in /proc/fs/ext4/<devname>
1314 ..............................................................................
1315 File Content
1316 mb_groups details of multiblock allocator buddy cache of free blocks
1317 ..............................................................................
1319 2.0 /proc/consoles
1320 ------------------
1321 Shows registered system console lines.
1323 To see which character device lines are currently used for the system console
1324 /dev/console, you may simply look into the file /proc/consoles:
1326 > cat /proc/consoles
1327 tty0 -WU (ECp) 4:7
1328 ttyS0 -W- (Ep) 4:64
1330 The columns are:
1332 device name of the device
1333 operations R = can do read operations
1334 W = can do write operations
1335 U = can do unblank
1336 flags E = it is enabled
1337 C = it is preferred console
1338 B = it is primary boot console
1339 p = it is used for printk buffer
1340 b = it is not a TTY but a Braille device
1341 a = it is safe to use when cpu is offline
1342 major:minor major and minor number of the device separated by a colon
1344 ------------------------------------------------------------------------------
1345 Summary
1346 ------------------------------------------------------------------------------
1347 The /proc file system serves information about the running system. It not only
1348 allows access to process data but also allows you to request the kernel status
1349 by reading files in the hierarchy.
1351 The directory structure of /proc reflects the types of information and makes
1352 it easy, if not obvious, where to look for specific data.
1353 ------------------------------------------------------------------------------
1355 ------------------------------------------------------------------------------
1356 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1357 ------------------------------------------------------------------------------
1359 ------------------------------------------------------------------------------
1360 In This Chapter
1361 ------------------------------------------------------------------------------
1362 * Modifying kernel parameters by writing into files found in /proc/sys
1363 * Exploring the files which modify certain parameters
1364 * Review of the /proc/sys file tree
1365 ------------------------------------------------------------------------------
1368 A very interesting part of /proc is the directory /proc/sys. This is not only
1369 a source of information, it also allows you to change parameters within the
1370 kernel. Be very careful when attempting this. You can optimize your system,
1371 but you can also cause it to crash. Never alter kernel parameters on a
1372 production system. Set up a development machine and test to make sure that
1373 everything works the way you want it to. You may have no alternative but to
1374 reboot the machine once an error has been made.
1376 To change a value, simply echo the new value into the file. An example is
1377 given below in the section on the file system data. You need to be root to do
1378 this. You can create your own boot script to perform this every time your
1379 system boots.
1381 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1382 general things in the operation of the Linux kernel. Since some of the files
1383 can inadvertently disrupt your system, it is advisable to read both
1384 documentation and source before actually making adjustments. In any case, be
1385 very careful when writing to any of these files. The entries in /proc may
1386 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1387 review the kernel documentation in the directory /usr/src/linux/Documentation.
1388 This chapter is heavily based on the documentation included in the pre 2.2
1389 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1391 Please see: Documentation/sysctl/ directory for descriptions of these
1392 entries.
1394 ------------------------------------------------------------------------------
1395 Summary
1396 ------------------------------------------------------------------------------
1397 Certain aspects of kernel behavior can be modified at runtime, without the
1398 need to recompile the kernel, or even to reboot the system. The files in the
1399 /proc/sys tree can not only be read, but also modified. You can use the echo
1400 command to write value into these files, thereby changing the default settings
1401 of the kernel.
1402 ------------------------------------------------------------------------------
1404 ------------------------------------------------------------------------------
1405 CHAPTER 3: PER-PROCESS PARAMETERS
1406 ------------------------------------------------------------------------------
1408 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1409 --------------------------------------------------------------------------------
1411 These file can be used to adjust the badness heuristic used to select which
1412 process gets killed in out of memory conditions.
1414 The badness heuristic assigns a value to each candidate task ranging from 0
1415 (never kill) to 1000 (always kill) to determine which process is targeted. The
1416 units are roughly a proportion along that range of allowed memory the process
1417 may allocate from based on an estimation of its current memory and swap use.
1418 For example, if a task is using all allowed memory, its badness score will be
1419 1000. If it is using half of its allowed memory, its score will be 500.
1421 There is an additional factor included in the badness score: the current memory
1422 and swap usage is discounted by 3% for root processes.
1424 The amount of "allowed" memory depends on the context in which the oom killer
1425 was called. If it is due to the memory assigned to the allocating task's cpuset
1426 being exhausted, the allowed memory represents the set of mems assigned to that
1427 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1428 memory represents the set of mempolicy nodes. If it is due to a memory
1429 limit (or swap limit) being reached, the allowed memory is that configured
1430 limit. Finally, if it is due to the entire system being out of memory, the
1431 allowed memory represents all allocatable resources.
1433 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1434 is used to determine which task to kill. Acceptable values range from -1000
1435 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1436 polarize the preference for oom killing either by always preferring a certain
1437 task or completely disabling it. The lowest possible value, -1000, is
1438 equivalent to disabling oom killing entirely for that task since it will always
1439 report a badness score of 0.
1441 Consequently, it is very simple for userspace to define the amount of memory to
1442 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1443 example, is roughly equivalent to allowing the remainder of tasks sharing the
1444 same system, cpuset, mempolicy, or memory controller resources to use at least
1445 50% more memory. A value of -500, on the other hand, would be roughly
1446 equivalent to discounting 50% of the task's allowed memory from being considered
1447 as scoring against the task.
1449 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1450 be used to tune the badness score. Its acceptable values range from -16
1451 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1452 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1453 scaled linearly with /proc/<pid>/oom_score_adj.
1455 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1456 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1457 requires CAP_SYS_RESOURCE.
1459 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1460 generation children with separate address spaces instead, if possible. This
1461 avoids servers and important system daemons from being killed and loses the
1462 minimal amount of work.
1465 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1466 -------------------------------------------------------------
1468 This file can be used to check the current score used by the oom-killer is for
1469 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1470 process should be killed in an out-of-memory situation.
1473 3.3 /proc/<pid>/io - Display the IO accounting fields
1474 -------------------------------------------------------
1476 This file contains IO statistics for each running process
1478 Example
1479 -------
1481 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1482 [1] 3828
1484 test:/tmp # cat /proc/3828/io
1485 rchar: 323934931
1486 wchar: 323929600
1487 syscr: 632687
1488 syscw: 632675
1489 read_bytes: 0
1490 write_bytes: 323932160
1491 cancelled_write_bytes: 0
1494 Description
1495 -----------
1497 rchar
1498 -----
1500 I/O counter: chars read
1501 The number of bytes which this task has caused to be read from storage. This
1502 is simply the sum of bytes which this process passed to read() and pread().
1503 It includes things like tty IO and it is unaffected by whether or not actual
1504 physical disk IO was required (the read might have been satisfied from
1505 pagecache)
1508 wchar
1509 -----
1511 I/O counter: chars written
1512 The number of bytes which this task has caused, or shall cause to be written
1513 to disk. Similar caveats apply here as with rchar.
1516 syscr
1517 -----
1519 I/O counter: read syscalls
1520 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1521 and pread().
1524 syscw
1525 -----
1527 I/O counter: write syscalls
1528 Attempt to count the number of write I/O operations, i.e. syscalls like
1529 write() and pwrite().
1532 read_bytes
1533 ----------
1535 I/O counter: bytes read
1536 Attempt to count the number of bytes which this process really did cause to
1537 be fetched from the storage layer. Done at the submit_bio() level, so it is
1538 accurate for block-backed filesystems. <please add status regarding NFS and
1539 CIFS at a later time>
1542 write_bytes
1543 -----------
1545 I/O counter: bytes written
1546 Attempt to count the number of bytes which this process caused to be sent to
1547 the storage layer. This is done at page-dirtying time.
1550 cancelled_write_bytes
1551 ---------------------
1553 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1554 then deletes the file, it will in fact perform no writeout. But it will have
1555 been accounted as having caused 1MB of write.
1556 In other words: The number of bytes which this process caused to not happen,
1557 by truncating pagecache. A task can cause "negative" IO too. If this task
1558 truncates some dirty pagecache, some IO which another task has been accounted
1559 for (in its write_bytes) will not be happening. We _could_ just subtract that
1560 from the truncating task's write_bytes, but there is information loss in doing
1561 that.
1564 Note
1565 ----
1567 At its current implementation state, this is a bit racy on 32-bit machines: if
1568 process A reads process B's /proc/pid/io while process B is updating one of
1569 those 64-bit counters, process A could see an intermediate result.
1572 More information about this can be found within the taskstats documentation in
1573 Documentation/accounting.
1575 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1576 ---------------------------------------------------------------
1577 When a process is dumped, all anonymous memory is written to a core file as
1578 long as the size of the core file isn't limited. But sometimes we don't want
1579 to dump some memory segments, for example, huge shared memory or DAX.
1580 Conversely, sometimes we want to save file-backed memory segments into a core
1581 file, not only the individual files.
1583 /proc/<pid>/coredump_filter allows you to customize which memory segments
1584 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1585 of memory types. If a bit of the bitmask is set, memory segments of the
1586 corresponding memory type are dumped, otherwise they are not dumped.
1588 The following 9 memory types are supported:
1589 - (bit 0) anonymous private memory
1590 - (bit 1) anonymous shared memory
1591 - (bit 2) file-backed private memory
1592 - (bit 3) file-backed shared memory
1593 - (bit 4) ELF header pages in file-backed private memory areas (it is
1594 effective only if the bit 2 is cleared)
1595 - (bit 5) hugetlb private memory
1596 - (bit 6) hugetlb shared memory
1597 - (bit 7) DAX private memory
1598 - (bit 8) DAX shared memory
1600 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1601 are always dumped regardless of the bitmask status.
1603 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1604 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1606 The default value of coredump_filter is 0x33; this means all anonymous memory
1607 segments, ELF header pages and hugetlb private memory are dumped.
1609 If you don't want to dump all shared memory segments attached to pid 1234,
1610 write 0x31 to the process's proc file.
1612 $ echo 0x31 > /proc/1234/coredump_filter
1614 When a new process is created, the process inherits the bitmask status from its
1615 parent. It is useful to set up coredump_filter before the program runs.
1616 For example:
1618 $ echo 0x7 > /proc/self/coredump_filter
1619 $ ./some_program
1621 3.5 /proc/<pid>/mountinfo - Information about mounts
1622 --------------------------------------------------------
1624 This file contains lines of the form:
1626 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1627 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1629 (1) mount ID: unique identifier of the mount (may be reused after umount)
1630 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1631 (3) major:minor: value of st_dev for files on filesystem
1632 (4) root: root of the mount within the filesystem
1633 (5) mount point: mount point relative to the process's root
1634 (6) mount options: per mount options
1635 (7) optional fields: zero or more fields of the form "tag[:value]"
1636 (8) separator: marks the end of the optional fields
1637 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1638 (10) mount source: filesystem specific information or "none"
1639 (11) super options: per super block options
1641 Parsers should ignore all unrecognised optional fields. Currently the
1642 possible optional fields are:
1644 shared:X mount is shared in peer group X
1645 master:X mount is slave to peer group X
1646 propagate_from:X mount is slave and receives propagation from peer group X (*)
1647 unbindable mount is unbindable
1649 (*) X is the closest dominant peer group under the process's root. If
1650 X is the immediate master of the mount, or if there's no dominant peer
1651 group under the same root, then only the "master:X" field is present
1652 and not the "propagate_from:X" field.
1654 For more information on mount propagation see:
1656 Documentation/filesystems/sharedsubtree.txt
1659 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1660 --------------------------------------------------------
1661 These files provide a method to access a tasks comm value. It also allows for
1662 a task to set its own or one of its thread siblings comm value. The comm value
1663 is limited in size compared to the cmdline value, so writing anything longer
1664 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1665 comm value.
1668 3.7 /proc/<pid>/task/<tid>/children - Information about task children
1669 -------------------------------------------------------------------------
1670 This file provides a fast way to retrieve first level children pids
1671 of a task pointed by <pid>/<tid> pair. The format is a space separated
1672 stream of pids.
1674 Note the "first level" here -- if a child has own children they will
1675 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1676 to obtain the descendants.
1678 Since this interface is intended to be fast and cheap it doesn't
1679 guarantee to provide precise results and some children might be
1680 skipped, especially if they've exited right after we printed their
1681 pids, so one need to either stop or freeze processes being inspected
1682 if precise results are needed.
1685 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1686 ---------------------------------------------------------------
1687 This file provides information associated with an opened file. The regular
1688 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1689 represents the current offset of the opened file in decimal form [see lseek(2)
1690 for details], 'flags' denotes the octal O_xxx mask the file has been
1691 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1692 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1693 for details].
1695 A typical output is
1697 pos: 0
1698 flags: 0100002
1699 mnt_id: 19
1701 All locks associated with a file descriptor are shown in its fdinfo too.
1703 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1705 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1706 pair provide additional information particular to the objects they represent.
1708 Eventfd files
1709 ~~~~~~~~~~~~~
1710 pos: 0
1711 flags: 04002
1712 mnt_id: 9
1713 eventfd-count: 5a
1715 where 'eventfd-count' is hex value of a counter.
1717 Signalfd files
1718 ~~~~~~~~~~~~~~
1719 pos: 0
1720 flags: 04002
1721 mnt_id: 9
1722 sigmask: 0000000000000200
1724 where 'sigmask' is hex value of the signal mask associated
1725 with a file.
1727 Epoll files
1728 ~~~~~~~~~~~
1729 pos: 0
1730 flags: 02
1731 mnt_id: 9
1732 tfd: 5 events: 1d data: ffffffffffffffff
1734 where 'tfd' is a target file descriptor number in decimal form,
1735 'events' is events mask being watched and the 'data' is data
1736 associated with a target [see epoll(7) for more details].
1738 Fsnotify files
1739 ~~~~~~~~~~~~~~
1740 For inotify files the format is the following
1742 pos: 0
1743 flags: 02000000
1744 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1746 where 'wd' is a watch descriptor in decimal form, ie a target file
1747 descriptor number, 'ino' and 'sdev' are inode and device where the
1748 target file resides and the 'mask' is the mask of events, all in hex
1749 form [see inotify(7) for more details].
1751 If the kernel was built with exportfs support, the path to the target
1752 file is encoded as a file handle. The file handle is provided by three
1753 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1754 format.
1756 If the kernel is built without exportfs support the file handle won't be
1757 printed out.
1759 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1761 For fanotify files the format is
1763 pos: 0
1764 flags: 02
1765 mnt_id: 9
1766 fanotify flags:10 event-flags:0
1767 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1768 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1770 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1771 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1772 flags associated with mark which are tracked separately from events
1773 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1774 mask and 'ignored_mask' is the mask of events which are to be ignored.
1775 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1776 does provide information about flags and mask used in fanotify_mark
1777 call [see fsnotify manpage for details].
1779 While the first three lines are mandatory and always printed, the rest is
1780 optional and may be omitted if no marks created yet.
1782 Timerfd files
1783 ~~~~~~~~~~~~~
1785 pos: 0
1786 flags: 02
1787 mnt_id: 9
1788 clockid: 0
1789 ticks: 0
1790 settime flags: 01
1791 it_value: (0, 49406829)
1792 it_interval: (1, 0)
1794 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1795 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1796 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1797 details]. 'it_value' is remaining time until the timer exiration.
1798 'it_interval' is the interval for the timer. Note the timer might be set up
1799 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1800 still exhibits timer's remaining time.
1802 3.9 /proc/<pid>/map_files - Information about memory mapped files
1803 ---------------------------------------------------------------------
1804 This directory contains symbolic links which represent memory mapped files
1805 the process is maintaining. Example output:
1807 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1808 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1809 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1810 | ...
1811 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1812 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1814 The name of a link represents the virtual memory bounds of a mapping, i.e.
1815 vm_area_struct::vm_start-vm_area_struct::vm_end.
1817 The main purpose of the map_files is to retrieve a set of memory mapped
1818 files in a fast way instead of parsing /proc/<pid>/maps or
1819 /proc/<pid>/smaps, both of which contain many more records. At the same
1820 time one can open(2) mappings from the listings of two processes and
1821 comparing their inode numbers to figure out which anonymous memory areas
1822 are actually shared.
1824 ------------------------------------------------------------------------------
1825 Configuring procfs
1826 ------------------------------------------------------------------------------
1828 4.1 Mount options
1829 ---------------------
1831 The following mount options are supported:
1833 hidepid= Set /proc/<pid>/ access mode.
1834 gid= Set the group authorized to learn processes information.
1836 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1837 (default).
1839 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1840 own. Sensitive files like cmdline, sched*, status are now protected against
1841 other users. This makes it impossible to learn whether any user runs
1842 specific program (given the program doesn't reveal itself by its behaviour).
1843 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1844 poorly written programs passing sensitive information via program arguments are
1845 now protected against local eavesdroppers.
1847 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1848 users. It doesn't mean that it hides a fact whether a process with a specific
1849 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1850 but it hides process' uid and gid, which may be learned by stat()'ing
1851 /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1852 information about running processes, whether some daemon runs with elevated
1853 privileges, whether other user runs some sensitive program, whether other users
1854 run any program at all, etc.
1856 gid= defines a group authorized to learn processes information otherwise
1857 prohibited by hidepid=. If you use some daemon like identd which needs to learn
1858 information about processes information, just add identd to this group.