buildroot/package/makedevs/README
Thomas Petazzoni 4e005c47e5 Allow several device tables and split in two parts our device table
This allows to have a device table for all directories/files and
another device table for the device files themselves. Both are needed
for static /dev, but only the first one is needed when
devtmpfs/mdev/udev are used.

We take this opportunity to move the documentation of the device table
format in a common location, package/makedevs/README.

[Peter: simplify code slightly, fix indentation]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
2011-05-09 16:52:22 +02:00

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When building a target filesystem, it is desirable to not have to
become root and then run 'mknod' a thousand times. Using a device
table you can create device nodes and directories "on the fly".
You can do all sorts of interesting things with a device table file.
For example, if you want to adjust the permissions on a particular
file you can just add an entry like:
/sbin/foobar f 2755 0 0 - - - - -
and (assuming the file /sbin/foobar exists) it will be made setuid
root (regardless of what its permissions are on the host filesystem.
Furthermore, you can use a single table entry to create a many device
minors. For example, if I wanted to create /dev/hda and
/dev/hda[0-15] I could just use the following two table entries:
/dev/hda b 640 0 0 3 0 0 0 -
/dev/hda b 640 0 0 3 1 1 1 15
Device table entries take the form of:
<name> <type> <mode> <uid> <gid> <major> <minor> <start> <inc> <count>
where name is the file name, type can be one of:
f A regular file
d Directory
c Character special device file
b Block special device file
p Fifo (named pipe)
uid is the user id for the target file, gid is the group id for the
target file. The rest of the entries (major, minor, etc) apply only
to device special files.