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

/usr/sbin/mount.lockfs is a symlink to /usr/libexec/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
       /usr/libexec/bilibop/lockfs_mount_helper
       /usr/share/doc/bilibop-lockfs/README.Debian

AUTHOR