< extracted from init.c >
/*
preinit - new try on 2002/04/20 - Willy Tarreau <willy AT meta-x.org>
usage : /sbin/preinit [ \< config_file ] [ { init args | "rebuild" } ]
Note : the "\< config_file" is to be used within configuration files :
#!/sbin/preinit <
....
Thus, when you pass "init=/.preinit", the kernel executes :
/sbin/preinit < /.preinit
The '<' character has been chosen for its rareness.
the "rebuild" argument make the tool only rebuild a complete /dev
tree from the informations contained in the .preinit file, and then
exit. It does this even if the pid is not 1, but doesn't execute nor
mount anything. Only mkdir, links, blocks, chars and fifo devices are
created. Very useful before a lilo :
# chroot /mnt/disk /.preinit rebuild
# lilo -r /mnt/disk
# umount /mnt/disk/dev
If /dev/console is found under /dev, it will not be rebuilt.
**** needs to rework the doc a bit since it's not up-to-date. ****
This code tries to build a few filesystem squeleton so that init has enough
to work correctly :
- mount -t proc /proc /proc
- mount -t tmpfs /dev /dev
- get information from a file : /.preinit which describes what to mount,
what ramdisks, links and dirs to make :
ln L source dest
make a symlink from <source> to <dest>
md D path [ mode ]
create a directory named <path> with the mode <mode>. If mode is left
undefined, 0755 is assumed.
mt M blkdev[(major:minor)] path fstype [ { ro | rw } [ flags ] ]
if <major:minor> is specified, create a block device <blkdev>
with <major> and <minor> and mode 0600.
mount <blkdev> under <path> with type <fstype>, read-only, except if
rw is specified, and args <flags>.
in I path
set the next init program to <path>
ex E cmd [ args ]*
execute <cmd> with args <args> and wait for its completion.
rx R dir cmd [ args ]*
chroot to <dir>, execute <cmd> with args <args> and wait for its completion.
bl B mode uid gid major minor naming_rule
create a set of block devices
ch C mode uid gid major minor naming_rule
create a set of char devices
fi F mode uid gid name
create a fifo
ma U mode
change umask
pr P <new_root> <put_old_relative>
pivot root : old root is displaced into new_root/put_old_relative, and
new_root is displaced under /.
mv K <old_dir> <new_dir>
keep directory <old_dir> after a pivot, then unmount it from old_dir.
usefull for /dev, /proc, /var ...
um O <old_dir>
umount <old_dir> after a pivot for example.
lo l </dev/loopX> <file>
losetup /dev/loopX file.
# anything
comment.
The devices naming rules consist in strings mixed with numbering rules delimited with
brackets. Each numbering rule has 4 comma-separated fields :
- type of this string portion : 'c' for a single char, 'i' for an int, 'I' for an int
for which 0 is not printed, 'h' for an hex digit
- the range :
- chars: any concatenation of character ranges separated with a dash '-': 'a-fk-npq'
- ints : either an int or a range composed of 2 ints separated with a dash : '1-16'
- hex : same as int, but with hex digits (case insensitive)
- the scale : how much to add to the minor device for each step in the range.
The commands may be prefixed with a '|' or '&', in which case, they will be
executed only if the previous command failed (|) or succeeded (&).
Example :
ln hda3 /dev/disk => symlinks /dev/disk to hda3
md /var/tmp 1777 => creates a directory /var/tmp with mode 1777
mt /dev/hda1 /boot ext2 => attempts to mount /dev/hda1 read-only under /boot.
|mt /dev/hda1(3:1) /boot ext2 => only if the previous command failed, creates /dev/hda1 with major 3, minor 1 and mounts it under /boot
in /sbin/init-std => the following init will be this /sbin/init-std (31 chars max)
ex /sbin/initramdisk /dev/ram6 1200 => executes /sbin/initramdisk with these args and waits for its completion
bl 0600 0 0 3 1 hd[c,ab,64][i,1-16,1] => makes all hdaX and hdbX with X ranging from 1 to 16
ch 0600 0 5 2 0 pty[c,p-za-f,16][h,0-f,1] => makes all 256 pty*
#comment => ignore this line
For executable reduction reasons, the .preinit file is limited to 4 kB.
*/
