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Major rewrite of mount, umount, losetup. Untangled lots of code, shrunk

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things down a bit, fixed a number of funky corner cases, added support for
several new features (things like mount --move, mount --bind, lazy unounts,
automatic detection of loop mounts, and so on).  Probably broke several
other things, but it's fixable.  (Bang on it, tell me what doesn't work for
you...)

Note: you no longer need to say "-o loop".  It does that for you when
necessary.

Still need to add "user mount" support, which involves making mount suid.  Not
too hard to do under the new infrastructure, just haven't done it yet...

The previous code had the following notes, that belong in the version
control comments:

- * 3/21/1999   Charles P. Wright <cpwright@cpwright.com>
- *             searches through fstab when -a is passed
- *             will try mounting stuff with all fses when passed -t auto
- *
- * 1999-04-17  Dave Cinege...Rewrote -t auto. Fixed ro mtab.
- *
- * 1999-10-07  Erik Andersen <andersen@codepoet.org>.
- *              Rewrite of a lot of code. Removed mtab usage (I plan on
- *              putting it back as a compile-time option some time),
- *              major adjustments to option parsing, and some serious
- *              dieting all around.
- *
- * 1999-11-06  mtab support is back - andersee
- *
- * 2000-01-12   Ben Collins <bcollins@debian.org>, Borrowed utils-linux's
- *              mount to add loop support.
- *
- * 2000-04-30  Dave Cinege <dcinege@psychosis.com>
- *             Rewrote fstab while loop and lower mount section. Can now do
- *             single mounts from fstab. Can override fstab options for single
- *             mount. Common mount_one call for single mounts and 'all'. Fixed
- *             mtab updating and stale entries. Removed 'remount' default.
- *
This commit is contained in:
Rob Landley
2005-08-10 20:35:54 +00:00
parent 0b62158475
commit 6a6798b8e4
12 changed files with 555 additions and 934 deletions
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57
util-linux/Config.in
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@ -323,54 +323,43 @@ config CONFIG_UMOUNT
the tool to use. If you enabled the 'mount' utility, you almost certainly
also want to enable 'umount'.
config CONFIG_FEATURE_MOUNT_FORCE
bool " Support forced filesystem unmounting"
default n
depends on CONFIG_UMOUNT
help
This allows you to _force_ a filesystem to be umounted. This is generally
only useful when you want to get rid of an unreachable NFS system.
comment "Common options for mount/umount"
depends on CONFIG_MOUNT || CONFIG_UMOUNT
config CONFIG_FEATURE_MOUNT_LOOP
bool " Support for loop devices"
bool " Support loopback mounts"
default n
depends on CONFIG_MOUNT || CONFIG_UMOUNT
help
Enabling this feature allows automatic loopback mounts, meaning you can mount
filesystems contained in normal files as well as in block devices. The mount
and umount commands will detect you are trying to mount a file instead of a
block device, and transparently associate it with a loopback device (and free
the loopback device on unmount) for you.
Enabling this feature allows automatic mounting of files (containing
filesystem images) via the linux kernel's loopback devices. The mount
command will detect you are trying to mount a file instead of a block
device, and transparently associate the file with a loopback device.
The umount command will also free that loopback device.
You can still use the 'losetup' utility and mount the loopback device yourself
if you need to do something advanced, such as specify an offset or cryptographic
options to the loopback device.
config CONFIG_FEATURE_MOUNT_LOOP_MAX
int " max number of loop devices"
default 7
depends on CONFIG_FEATURE_MOUNT_LOOP
help
This option sets the highest numbered loop device to be used
automatically by the '-o loop' feature of mount.
You can still use the 'losetup' utility (to manually associate files
with loop devices) if you need to do something advanced, such as
specify an offset or cryptographic options to the loopback device.
(If you don't want umount to free the loop device, use "umount -D".)
config CONFIG_FEATURE_MTAB_SUPPORT
bool " Support for a /etc/mtab file (instead of symlink to /proc/mounts)"
bool " Support for the old /etc/mtab file"
default n
depends on CONFIG_MOUNT || CONFIG_UMOUNT
help
If your root filesystem is writable and you wish to have the 'mount'
utility create an mtab file listing the filesystems which have been
mounted then you should enable this option. Most people that use
BusyBox have a read-only root filesystem, so they will leave this
option disabled and BusyBox will use the /proc/mounts file.
Historically, Unix systems kept track of the currently mounted
partitions in the file "/etc/mtab". These days, the kernel exports
the list of currently mounted partitions in "/proc/mounts", rendering
the old mtab file obsolete. (In modern systems, /etc/mtab should be
a symlink to /proc/mounts.)
Note that even non-embedded developers probably want to have /etc/mtab
be a symlink to /proc/mounts, since otherwise mtab can get out of sync
with the real kernel mount state in numerous ways.
The only reason to have mount maintain an /etc/mtab file itself is if
your stripped-down embedded system does not have a /proc directory.
If you must use this, keep in mind it's inherently brittle (for
example a mount under chroot won't update it), can't handle modern
features like separate per-process filesystem namespaces, requires
that your /etc directory be writeable, tends to get easily confused
by --bind or --move mounts, and so on. (In brief: avoid.)
config CONFIG_READPROFILE
bool "readprofile"