Ubuntu Manpage: mount.lockfs - helper script for the mount command

NAME

       mount.lockfs - helper script for the mount command

SYNOPSIS

       mount.lockfs FILESYSTEM MOUNTPOINT [MOUNTFLAGS] -o MOUNTOPTIONS

DESCRIPTION

/sbin/mount.lockfs is a symlink to /lib/bilibop/lockfs_mount_helper. It is used as an
helper program by the mount(8) command for the 'lockfs' filesystem type entries in
/etc/fstab. This script cannot be run manually, and fails if the root filesystem is not
already managed by bilibop-lockfs. The expected way to run it and how it does its job are
the followings:

1. Enable bilibop-lockfs: set the BILIBOP_LOCKFS variable to true in bilibop.conf(5) and
reboot the computer; or reboot the computer and append the 'lockfs' kernel parameter to
the boot commandline.

2. One time the future '/' is set as an union filesystem mountpoint from into the
initramfs environment, the temporary and writable fstab(5) on it is modified to replace
filesystem types of some entries by 'lockfs'. Options are also modified to remember
the original fstype.

3. One time the union mount is the new root filesystem, initscripts are executed: fstab(5)
is parsed by 'mount -a', and then mount(8) calls mount.lockfs with the proper arguments
when a 'lockfs' fstype is encountered.

4. mount.lockfs parses arguments and checks if the filesystem has been whitelisted in
bilibop.conf(5), or not. If it is the case, the filesystem is mounted normally and the
fstab entry is modified to reflect the actual mount call. If neither the filesystem nor
the mountpoint have been whitelisted, then the filesystem is mounted elsewhere and
readonly, a temporary filesystem is mounted with proper options, size, permissions and
ownership, and an aufs or overlay filesystem (depending on the version of your kernel)
is mounted on the MOUNTPOINT given as argument with the lower/readonly and
upper/writable branches previously set. The fstab entry is replaced by three lines
reflecting the actual mount calls. If something fails, mount.lockfs acts as if the
filesystem was whitelisted. See /usr/share/doc/bilibop-lockfs/README.Debian for
details.

OPTIONS

       lockfs_mount_helper uses options and arguments as they are given by mount(8) after it  has
       parsed  the  corresponding  fstab(5) entry. So, options and arguments are mandatory, mount
       flags are optional, and all come in the following order:

       FILESYSTEM
              Corresponding to the first field in fstab. This  must  be  a  block  device,  or  a
              symlink to a block device. If this field is given with one of the UUID=* or LABEL=*
              formats, then the mount command translates it  to  the  corresponding  device  name
              before to call the helper program.

       MOUNTPOINT
              Corresponding to the second field in fstab.

       [MOUNTFLAGS]
              Generic flags passed to the mount commandline (the most usual being -v and -n).

       -o MOUNTOPTIONS
              Corresponding  to  the  fourth  field in fstab. The mount options are parsed by the
              helper script: if fstype=* is encountered, it is removed from the options and  used
              to  mount  the  readonly branch with this filesystem type. If ro, noexec, nosuid or
              nodev options are encountered, they are added to the list of mount options  of  the
              writable branch.

FILES

       /etc/fstab
       /lib/bilibop/lockfs_mount_helper
       /usr/share/doc/bilibop-lockfs/README.Debian

AUTHOR