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67 lines
2.2 KiB
67 lines
2.2 KiB
#!/bin/sh
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dir="$1"
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dev="$2"
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if [ "$1" = "--help" ] || [ ! -d "${dir}" ]; then
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echo "Usage: $0 dir [mke2fs args] dev"
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exit 1
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fi
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shift
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# Goal: Put all the files at the beginning (which mke2fs does) and minimize
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# the number of free inodes given the minimum number of blocks required.
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# Hence all this math to get the inode ratio just right.
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bytes="$(du -ks "${dir}" | awk '{print $1}')"
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bytes="$((bytes * 1024))"
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inodes="$(find "${dir}" -print0 | xargs -0 stat -c '%i' | sort -g | uniq | wc -l)"
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block_sz=4096
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inode_sz=256
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sb_overhead=4096
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blocks_per_group="$((block_sz * 8))"
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bytes_per_group="$((blocks_per_group * block_sz))"
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inode_bytes="$((inodes * inode_sz))"
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# Estimate overhead with the minimum number of groups...
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nr_groups="$(( (bytes + inode_bytes + bytes_per_group - 1) / bytes_per_group))"
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inode_bytes_per_group="$((inode_bytes / nr_groups))"
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inode_blocks_per_group="$(( (inode_bytes_per_group + (block_sz - 1)) / block_sz ))"
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per_grp_overhead="$(( ((3 + inode_blocks_per_group) * block_sz) + 64 ))"
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overhead="$(( sb_overhead + (per_grp_overhead * nr_groups) ))"
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used_bytes="$((bytes + overhead))"
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# Then do it again with the real number of groups.
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nr_groups="$(( (used_bytes + (bytes_per_group - 1)) / bytes_per_group))"
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tot_blocks="$((nr_groups * blocks_per_group))"
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tot_bytes="$((tot_blocks * block_sz))"
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ratio="$((bytes / inodes))"
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mkfs_blocks="$((tot_blocks * 4 / 3))"
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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
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e2fsck -fyD "${dev}"
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blocks="$(dumpe2fs -h "${dev}" 2>&1 | grep 'Block count:' | awk '{print $3}')"
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while resize2fs -f -M "${dev}"; do
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new_blocks="$(dumpe2fs -h "${dev}" 2>&1 | grep 'Block count:' | awk '{print $3}')"
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if [ "${new_blocks}" -eq "${blocks}" ]; then
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break;
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fi
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blocks="${new_blocks}"
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done
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if [ ! -b "${dev}" ]; then
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truncate -s "$((blocks * block_sz))" "${dev}" || (e2image -ar "${dev}" "${dev}.min"; mv "${dev}.min" "${dev}")
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fi
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e2fsck -fy "${dev}"
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dir_blocks="$((bytes / block_sz))"
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overhead="$((blocks - dir_blocks))"
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echo "Minimized image overhead: $((100 * overhead / dir_blocks))%"
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exit 0
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