contrib/dir2fs

   1 #!/bin/sh
   2
   3 dir="$1"
   4 dev="$2"
   5
   6 if [ "$1" = "--help" ] || [ ! -d "${dir}" ]; then
   7         echo "Usage: $0 dir [mke2fs args] dev"
   8         exit 1
   9 fi
  10
  11 shift
  12
  13 # Goal: Put all the files at the beginning (which mke2fs does) and minimize
  14 # the number of free inodes given the minimum number of blocks required.
  15 # Hence all this math to get the inode ratio just right.
  16
  17 bytes="$(du -ks "${dir}" | awk '{print $1}')"
  18 bytes="$((bytes * 1024))"
  19 inodes="$(find "${dir}" -print0 | xargs -0 stat -c '%i' | sort -g | uniq | wc -l)"
  20 block_sz=4096
  21 inode_sz=256
  22 sb_overhead=4096
  23 blocks_per_group="$((block_sz * 8))"
  24 bytes_per_group="$((blocks_per_group * block_sz))"
  25 inode_bytes="$((inodes * inode_sz))"
  26
  27 # Estimate overhead with the minimum number of groups...
  28 nr_groups="$(( (bytes + inode_bytes + bytes_per_group - 1) / bytes_per_group))"
  29 inode_bytes_per_group="$((inode_bytes / nr_groups))"
  30 inode_blocks_per_group="$(( (inode_bytes_per_group + (block_sz - 1)) / block_sz ))"
  31 per_grp_overhead="$(( ((3 + inode_blocks_per_group) * block_sz) + 64 ))"
  32 overhead="$(( sb_overhead + (per_grp_overhead * nr_groups) ))"
  33 used_bytes="$((bytes + overhead))"
  34
  35 # Then do it again with the real number of groups.
  36 nr_groups="$(( (used_bytes + (bytes_per_group - 1)) / bytes_per_group))"
  37 tot_blocks="$((nr_groups * blocks_per_group))"
  38 tot_bytes="$((tot_blocks * block_sz))"
  39
  40 ratio="$((bytes / inodes))"
  41 mkfs_blocks="$((tot_blocks * 4 / 3))"
  42
  43 mke2fs -i "${ratio}" -T ext4 -d "${dir}" -O ^resize_inode,sparse_super2,metadata_csum,64bit,^has_journal -E packed_meta_blocks=1,num_backup_sb=0 -b "${block_sz}" -I "${inodesz}" -F "${dev}" "${mkfs_blocks}" || exit
  44
  45 e2fsck -fyD "${dev}"
  46
  47 blocks="$(dumpe2fs -h "${dev}" 2>&1 | grep 'Block count:' | awk '{print $3}')"
  48 while resize2fs -f -M "${dev}"; do
  49         new_blocks="$(dumpe2fs -h "${dev}" 2>&1 | grep 'Block count:' | awk '{print $3}')"
  50         if [ "${new_blocks}" -eq "${blocks}" ]; then
  51                 break;
  52         fi
  53         blocks="${new_blocks}"
  54 done
  55
  56 if [ ! -b "${dev}" ]; then
  57     truncate -s "$((blocks * block_sz))" "${dev}" || (e2image -ar "${dev}" "${dev}.min"; mv "${dev}.min" "${dev}")
  58 fi
  59
  60 e2fsck -fy "${dev}"
  61
  62 dir_blocks="$((bytes / block_sz))"
  63 overhead="$((blocks - dir_blocks))"
  64 echo "Minimized image overhead: $((100 * overhead / dir_blocks))%"
  65
  66 exit 0