xref: /aosp_15_r20/external/squashfs-tools/RELEASE-READMEs/pseudo-file.example (revision 79398b2563bcbbbab54656397863972d8fa68df1)

# Pseudo file example

# Mksquashfs supports pseudo files, these allow fake files, directories,
# character and block devices to be specified and added to the Squashfs
# filesystem being built, rather than requiring them to be present in the
# source directories.
#
# This, for example, allows device nodes to be added to the filesystem without
# requiring root access.

# Mksquashfs 4.1 adds support for "dynamic pseudo files" and a modify operation.
# Dynamic pseudo files allow files to be dynamically created when Mksquashfs
# is run, their contents being the result of running a command or piece of
# shell script.  The modifiy operation allows the mode/uid/gid of an existing
# file in the source filesystem to be modified.

# Two Mksquashfs options are supported, -p allows one pseudo file to be
# specified #on the command line, and -pf allows a pseudo file to be specified
# containing a list of pseduo definitions, one per line.

# Pseudo file examples
# Run mkquashfs . /tmp/img -pf pseudo-file.examples
# to see their effect

# Creating dynamic file examples

# Create a file "dmesg" containing the output from dmesg.
dmesg f 444 root root dmesg


# Create a file RELEASE containing the release name, date, build host, and
# an incrementing version number.  The incrementing version is a side-effect
# of executing the shell script, and ensures every time Mksquashfs is run a
# new version number is used without requiring any other shell scripting.
RELEASE f 444 root root \
		if [ ! -e /tmp/ver ]; then \
			echo 0 > /tmp/ver; \
		fi; \
                ver=`cat /tmp/ver`; \
                ver=$((ver +1)); \
                echo $ver > /tmp/ver; \
                echo -n "release x.x"; \
                echo "-dev #"$ver `date` "Build host" `hostname`


# Copy 10K from the device /dev/sda1 into the file input.  Ordinarily
# Mksquashfs given a device, fifo, or named socket will place that special file
# within the Squashfs filesystem, this allows input from these special
# files to be captured and placed in the Squashfs filesystem.
input f 444 root root dd if=/dev/sda1 bs=1024 count=10


# Creating a block or character device examples

# Create a character device "chr_dev" with major:minor 100:1 and
# a block device "blk_dev" with major:minor 200:200, both with root
# uid/gid and a mode of rw-rw-rw.
chr_dev c 666 root root 100 1
blk_dev b 666 0 0 200 200


# Creating a directory example

# create a directory "pseudo_dir" with root uid/gid and mode of r--r--r--.
pseudo_dir d 444 root root


# Modifying attributes of an existing file exmaple

# Change the attributes of the file "INSTALL" in the filesystem to have
# root uid/gid and a mode of rw-rw-rw, overriding the attributes obtained
# from the source filesystem.
INSTALL m 666 root root