Ubuntu Manpage: mkfs.erofs - tool to create an EROFS filesystem

NAME

       mkfs.erofs - tool to create an EROFS filesystem

SYNOPSIS

       mkfs.erofs [OPTIONS] DESTINATION SOURCE

DESCRIPTION

       EROFS is a new enhanced lightweight linux read-only filesystem with modern designs (eg. no
       buffer head, reduced metadata, inline xattrs/data, etc.) for scenarios  which  need  high-
       performance read-only requirements, e.g. Android OS for smartphones and LIVECDs.

       It  also  provides fixed-sized output compression support, which improves storage density,
       keeps relatively  higher  compression  ratios,  which  is  more  useful  to  achieve  high
       performance  for  embedded  devices  with  limited  memory since it has unnoticable memory
       overhead and page cache thrashing.

       mkfs.erofs is used to create such EROFS filesystem  DESTINATION  image  file  from  SOURCE
       directory.

OPTIONS

-z compression-algorithm [,#] [: ... ]
Set a primary algorithm for data compression, which can be set with an optional
compression level (1 to 12 for LZ4HC, 0 to 9 for LZMA and 100 to 109 for LZMA
extreme compression) separated by a comma. Alternative algorithms could be
specified and separated by colons.

-C max-pcluster-size
Specify the maximum size of compress physical cluster in bytes. It may enable big
pcluster feature if needed (Linux v5.13+).

-d # Specify the level of debugging messages. The default is 2, which shows basic
warning messages.

-x # Specify the upper limit of an xattr which is still inlined. The default is 2.
Disable storing xattrs if < 0.

-E extended-option [,...]
Set extended options for the filesystem. Extended options are comma separated, and
may take an extra argument using the equals ('=') sign. The following extended
options are supported:

all-fragments
Forcely record the whole files into a special inode for better
compression and it may take an argument as the pcluster size of the
packed inode in bytes. (Linux v6.1+)

dedupe Enable global compressed data deduplication to minimize duplicated data
in the filesystem. It may be used with -Efragments option together to
further reduce image sizes. (Linux v6.1+)

force-inode-compact
Forcely generate compact inodes (32-byte inodes) to output.

force-inode-extended
Forcely generate extended inodes (64-byte inodes) to output.

force-inode-blockmap
Forcely generate inode chunk format in 4-byte block address array.

force-chunk-indexes
Forcely generate inode chunk format in 8-byte chunk indexes (with
device id).

fragments
Pack the tail part (pcluster) of compressed files or the whole files
into a special inode for smaller image sizes, and it may take an
argument as the pcluster size of the packed inode in bytes. (Linux
v6.1+)

legacy-compress
Drop "inplace decompression" and "compacted indexes" support, which is
used to generate compatible EROFS images for Linux v4.19 - 5.3.

noinline_data
Don't inline regular files to enable FSDAX for these files (Linux
v5.15+).

ztailpacking
Pack the tail part (pcluster) of compressed files into its metadata to
save more space and the tail part I/O. (Linux v5.17+)

-L volume-label
Set the volume label for the filesystem to volume-label. The maximum length of the
volume label is 16 bytes.

-T # Set all files to the given UNIX timestamp. Reproducible builds requires setting all
to a specific one.

-U UUID
Set the universally unique identifier (UUID) of the filesystem to UUID. The format
of the UUID is a series of hex digits separated by hyphens, like this:
"c1b9d5a2-f162-11cf-9ece-0020afc76f16".

--all-root
Make all files owned by root.

--blobdev file
Specify another extra blob device to store chunk-based data.

--chunksize #
Generate chunk-based files with #-byte chunks.

--compress-hints file
If the optional --compress-hints file argument is given, mkfs.erofs uses it to
apply the per-file compression strategy. Each line is defined by tokens separated
by spaces in the following form. Optionally, instead of the given primary
algorithm, alternative algorithms could be specified with algorithm-index by hand:
<pcluster-in-bytes> [algorithm-index] <match-pattern>

--exclude-path=path
Ignore file that matches the exact literal path. You may give multiple `--exclude-
path' options.

--exclude-regex=regex
Ignore files that match the given regular expression. You may give multiple
`--exclude-regex` options.

--file-contexts=file
Specify a file_contexts file to setup / override selinux labels.

--force-uid=UID
Set all file uids to UID.

--force-gid=GID
Set all file gids to GID.

--gid-offset=GIDOFFSET
Add GIDOFFSET to all file gids. When this option is used together with --force-
gid, the final file gids are set to GID + GID-OFFSET.

--help Display this help and exit.

--ignore-mtime
File modification time is ignored whenever it would cause mkfs.erofs to use
extended inodes over compact inodes. When not using a fixed timestamp, this can
reduce total metadata size.

--max-extent-bytes #
Specify maximum decompressed extent size # in bytes.

--preserve-mtime
File modification time is preserved whenever mkfs.erofs decides to use extended
inodes over compact inodes.

--uid-offset=UIDOFFSET
Add UIDOFFSET to all file uids. When this option is used together with --force-
uid, the final file uids are set to UID + UIDOFFSET.

AUTHOR

       This version of  mkfs.erofs  is  written  by  Li  Guifu  <blucerlee@gmail.com>,  Miao  Xie
       <miaoxie@huawei.com>  and Gao Xiang <xiang@kernel.org> with continuously improvements from
       others.

       This manual page was written by Gao Xiang <xiang@kernel.org>.

AVAILABILITY