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

Provided by: erofs-utils_1.7.1-1build2_amd64

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.

-b block-size
Set the fundamental block size of the filesystem in bytes. In other words, specify the smallest
amount of data that can be accessed at a time. The default is the system page size. It cannot be
less than 512 bytes.

-C max-pcluster-size
Specify the maximum size of compress physical cluster in bytes. This may cause the big pcluster
feature to be enabled (Linux v5.13+).

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

-x # Limit how many xattrs will be inlined. The default is 2. Disables 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. May further reduce image size when used with -E fragments. (Linux v6.1+)

force-inode-compact
Force generation of compact (32-byte) inodes.

force-inode-extended
Force generation of extended (64-byte) inodes.

force-inode-blockmap
Force generation of inode chunk format as a 4-byte block address array.

force-chunk-indexes
Forcely generate inode chunk format as an 8-byte chunk index (with device ID).

fragments[=size]
Pack the tail part (pcluster) of compressed files, or entire 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
Disable "inplace decompression" and "compacted indexes", for compatibility with Linux
pre-v5.4.

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

^xattr-name-filter
Turn off/on xattr name filter to optimize negative xattr lookups (Linux v6.6+).

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 require setting all to a specific
one. By default, the source file's modification time is used.

-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 an extra blob device to store chunk-based data.

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

--compress-hints file
Apply a per-file compression strategy. Each line in file is defined by tokens separated by spaces
in the following form. Optionally, instead of the given primary algorithm, alternative algorithms
can be specified with algorithm-index explicitly:
<pcluster-size-in-bytes> [algorithm-index] <match-pattern>
match-patterns are extended regular expressions, matched against absolute paths within the output
filesystem, with no leading /.

--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 extended regular expression. You may give multiple --exclude-
regex options.

--file-contexts=file
Read SELinux label configuration/overrides from file in the selinux_file(5) format.

--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.

--gzip Filter tarball streams through gzip.

--help Display help string and exit.

--ignore-mtime
Ignore the file modification time 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. Implied by
-E force-inode-compact.

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

--preserve-mtime
Use extended inodes instead of compact inodes if the file modification time would overflow compact
inodes. This is the default. Overrides --ignore-mtime.

--tar=f
Generate a full EROFS image from a tarball.

--tar=i
Generate an meta-only EROFS image from a tarball.

--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.

--xattr-prefix=PREFIX
Specify a customized extended attribute namespace prefix for space saving, e.g.
"trusted.overlay.". You may give multiple --xattr-prefix options (Linux v6.4+).

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