blob: d811f20a1d45825056cfef19bc014d649668fd57 [file] [log] [blame]
.\" Copyright (c) 2019 Gao Xiang <>
mkfs.erofs \- tool to create an EROFS filesystem
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 \fIDESTINATION\fR image file
from \fISOURCE\fR directory.
.BI "\-z " compression-algorithm " [" ",#" "]"
Set an algorithm for file compression, which can be set with an optional
compression level separated by a comma.
.BI "\-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+).
.BI "\-d " #
Specify the level of debugging messages. The default is 2, which shows basic
warning messages.
.BI "\-x " #
Specify the upper limit of an xattr which is still inlined. The default is 2.
Disable storing xattrs if < 0.
.BI "\-E " extended-option " [,...]"
Set extended options for the filesystem. Extended options are comma separated,
and may take an argument using the equals ('=') sign.
The following extended options are supported:
.RS 1.2i
.BI force-inode-compact
Forcely generate compact inodes (32-byte inodes) to output.
.BI force-inode-extended
Forcely generate extended inodes (64-byte inodes) to output.
.BI force-inode-blockmap
Forcely generate inode chunk format in 4-byte block address array.
.BI force-chunk-indexes
Forcely generate inode chunk format in 8-byte chunk indexes (with device id).
.BI legacy-compress
Drop "inplace decompression" and "compacted indexes" support, which is used
to generate compatible EROFS images for Linux v4.19 - 5.3.
.BI noinline_data
Don't inline regular files to enable FSDAX for these files (Linux v5.15+).
.BI 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+)
.BI "\-T " #
Set all files to the given UNIX timestamp. Reproducible builds requires setting
all to a specific one.
.BI "\-U " UUID
Set the universally unique identifier (UUID) of the filesystem to
The format of the UUID is a series of hex digits separated by hyphens,
like this: "c1b9d5a2-f162-11cf-9ece-0020afc76f16".
.B \-\-all-root
Make all files owned by root.
.BI "\-\-blobdev " file
Specify another extra blob device to store chunk-based data.
.BI "\-\-chunksize " #
Generate chunk-based files with #-byte chunks.
.BI "\-\-compress-hints " file
If the optional
.BI "\-\-compress-hints " file
argument is given,
.B mkfs.erofs
uses it to apply the per-file compression strategy. Each line is defined by
tokens separated by spaces in the following form:
.RS 1.2i
<pcluster-in-bytes> <match-pattern>
.BI "\-\-exclude-path=" path
Ignore file that matches the exact literal path.
You may give multiple `--exclude-path' options.
.BI "\-\-exclude-regex=" regex
Ignore files that match the given regular expression.
You may give multiple `--exclude-regex` options.
.BI "\-\-file-contexts=" file
Specify a \fIfile_contexts\fR file to setup / override selinux labels.
.BI "\-\-force-uid=" UID
Set all file uids to \fIUID\fR.
.BI "\-\-force-gid=" GID
Set all file gids to \fIGID\fR.
.B \-\-help
Display this help and exit.
.B "\-\-ignore-mtime"
File modification time is ignored whenever it would cause \fBmkfs.erofs\fR to
use extended inodes over compact inodes. When not using a fixed timestamp, this
can reduce total metadata size.
.BI "\-\-max-extent-bytes " #
Specify maximum decompressed extent size # in bytes.
.B "\-\-preserve-mtime"
File modification time is preserved whenever \fBmkfs.erofs\fR decides to use
extended inodes over compact inodes.
This version of \fBmkfs.erofs\fR is written by Li Guifu <>,
Miao Xie <> and Gao Xiang <> with
continuously improvements from others.
This manual page was written by Gao Xiang <>.
\fBmkfs.erofs\fR is part of erofs-utils package and is available from
.BR mkfs (8).