# erofs compression

```bash
#!/bin/bash
set -x

# Algorithms are listed in erofs-utils:lib/compressor.c.
# The best level for each algorithm is listed in erofs-utils:lib/compressor_${alg}.c:.best_level.
choices=(
	lz4      # doesn't take a level argument (.setlevel is NULL)
	lz4hc,12 # /usr/include/lz4hc.h
	lzma,109 # compressor_liblzma.c
	deflate,9
	libdeflate,12
)

time zstd mario.img # creates mario.img.zst

mkdir mnt
sudo mount -o loop mario.img mnt
for choice in "${choices[@]}"; do
	time sudo mkfs.erofs -z"${choice}" mario-"${choice/,/-}.img" mnt
done
```

  | 1.6G | mario.img               |   1m7s | Non-compressed
  |------+-------------------------+--------|
  | 904M | mario.img.zst           |     4s | For comparison
  |------+-------------------------+--------|
  | 1.2G | mario-lz4.img           |    53s |
  | 1.1G | mario-lz4hc-12.img      |  2m18s |
  | 957M | mario-lzma-109.img      | 10m17s |
  | 997M | mario-deflate-9.img     |  2m25s |
  | 0    | mario-libdeflate-12.img |      - | (compiled without libdeflate support) 

```
/home
/var/lib
/var/log
/var/cache

/etc/ssl/certs/
/etc/ca-certificates/extracted/
/etc/letsencrypt/
/root/
/usr/lib/utempter/utempter
/usr/bin/groupmems
/etc/ssh/ssh_host_*_key{,.pub}
```