SQUASHFS/squashfs-tools-4.4/RELEASE-READMEs/pseudo-file.example

   1 # Pseudo file example
   2
   3 # Mksquashfs supports pseudo files, these allow fake files, directories,
   4 # character and block devices to be specified and added to the Squashfs
   5 # filesystem being built, rather than requiring them to be present in the
   6 # source directories.
   7 #
   8 # This, for example, allows device nodes to be added to the filesystem without
   9 # requiring root access.
  10
  11 # Mksquashfs 4.1 adds support for "dynamic pseudo files" and a modify operation.
  12 # Dynamic pseudo files allow files to be dynamically created when Mksquashfs
  13 # is run, their contents being the result of running a command or piece of
  14 # shell script.  The modifiy operation allows the mode/uid/gid of an existing
  15 # file in the source filesystem to be modified.
  16
  17 # Two Mksquashfs options are supported, -p allows one pseudo file to be
  18 # specified #on the command line, and -pf allows a pseudo file to be specified
  19 # containing a list of pseduo definitions, one per line.
  20
  21 # Pseudo file examples
  22 # Run mkquashfs . /tmp/img -pf pseudo-file.examples
  23 # to see their effect
  24
  25 # Creating dynamic file examples
  26
  27 # Create a file "dmesg" containing the output from dmesg.
  28 dmesg f 444 root root dmesg
  29
  30
  31 # Create a file RELEASE containing the release name, date, build host, and
  32 # an incrementing version number.  The incrementing version is a side-effect
  33 # of executing the shell script, and ensures every time Mksquashfs is run a
  34 # new version number is used without requiring any other shell scripting.
  35 RELEASE f 444 root root \
  36                 if [ ! -e /tmp/ver ]; then \
  37                         echo 0 > /tmp/ver; \
  38                 fi; \
  39                 ver=`cat /tmp/ver`; \
  40                 ver=$((ver +1)); \
  41                 echo $ver > /tmp/ver; \
  42                 echo -n "release x.x"; \
  43                 echo "-dev #"$ver `date` "Build host" `hostname`
  44
  45
  46 # Copy 10K from the device /dev/sda1 into the file input.  Ordinarily
  47 # Mksquashfs given a device, fifo, or named socket will place that special file
  48 # within the Squashfs filesystem, this allows input from these special
  49 # files to be captured and placed in the Squashfs filesystem.
  50 input f 444 root root dd if=/dev/sda1 bs=1024 count=10
  51
  52
  53 # Creating a block or character device examples
  54
  55 # Create a character device "chr_dev" with major:minor 100:1 and
  56 # a block device "blk_dev" with major:minor 200:200, both with root
  57 # uid/gid and a mode of rw-rw-rw.
  58 chr_dev c 666 root root 100 1
  59 blk_dev b 666 0 0 200 200
  60
  61
  62 # Creating a directory example
  63
  64 # create a directory "pseudo_dir" with root uid/gid and mode of r--r--r--.
  65 pseudo_dir d 444 root root
  66
  67
  68 # Modifying attributes of an existing file exmaple
  69
  70 # Change the attributes of the file "INSTALL" in the filesystem to have
  71 # root uid/gid and a mode of rw-rw-rw, overriding the attributes obtained
  72 # from the source filesystem.
  73 INSTALL m 666 root root
  74