TITLE: Setting up Automount
LFS VERSION: Any
AUTHOR: R. Cort Tompkins <rtompkin@cs.odu.edu>
SPECIAL THANKS TO:
Tan Siong Hua <stsh@pd.jaring.my>
SYNOPSIS:
The mounting and unmounting of removable media is a tedious task,
especially when it needs to be done by unprivileged users. Automount is a
utility that will automatically unmount specified devices after a given
interval, and then remount them automatically upon subsequent access. This
makes the mount/unmount process relatively transparent to the end user.
HINT:
To get started you'll need a few things:
1) Automount support in the kernel. This is compiled into the kernel by
default unless you explicitly removed it during kernel configuration. If this
is the case, reconfigure your kernel (i.e. "make menuconfig" in your kernel
source directory) and enable Automount v4 as a built-in feature under the
"File Systems" heading.
2) The automount user utilities. Download the latest version 3 utilities from
ftp://ftp.kernel.org/pub/linux/daemons/autofs (autofs-3.1.7.tar.bz2 at the time
of this writing). Extract this archive and cd into it. Before compilation
and installation, we'll take preemptive action to stop a compile-time error:
$ cp modules/lookup_program.c modules/lookup_program.c.old
$ sed "s/OPEN_MAX/FOPEN_MAX/" modules/lookup_program.c.old > \
modules/lookup_program.c
$ ./configure --prefix=/usr --sbindir=/sbin
$ make
$ make install
If you look in the sample subdirectory, you'll find rc.autofs, a startup script
designed to help automate the automounting process. Use this if you wish, but
I will give instructions for creating a slightly simpler script which should
help you better understand the workings of automount.
First we'll create the script itself, as root:
$ cat > /etc/rc.d/init.d/auto_mount << "EOF"
#!/bin/bash
# Begin /etc/rc.d/init.d/auto_mount
#
# Automount script by Cort Tompkins - rtompkin@cs.odu.edu, derived
# from ethnet script by Gerard Beekmans - gerard@linuxfromscratch.org
source /etc/rc.d/init.d/functions
case "$1" in
start)
for mountspec in $(/bin/ls /etc/sysconfig/automount-config/*.auto)
do
source $mountspec
MOUNT_BASE=${mountspec%.auto}
echo "Starting automount for group ${MOUNT_BASE##*/} ..."
/sbin/automount --timeout=${TIMEOUT} $MOUNTPOINT file \
$MOUNT_BASE.map
evaluate_retval
done
;;
# assume all instances of automount were started by this script
stop)
echo -n "Stopping automount ..."
# Unmount everything mounted by automount
/bin/killall -USR1 automount
/bin/killall automount
evaluate_retval
;;
restart)
$0 stop
sleep 1
$0 start
;;
*)
echo "Usage: $0 {start|stop|restart}"
exit 1
;;
esac
# End /etc/rc.d/init.d/auto_mount
EOF
Please resist the temptation to name the startup script "automount." This
means that the script will get the same kill signals we send to automount
proper.
Give the script proper permissions:
$ chmod 754 /etc/rc.d/init.d/auto_mount
Since I use automount for network shares, I only want it to be running when
in a networkable state. On the very rare occasion that you find yourself in
an unnetworked runlevel, you can always mount your removable devices manually.
$ cd /etc/rc.d
$ for rl in $(seq 0 2; echo 6); do
> cd rc${rl}.d
> ln -s ../init.d/auto_mount K45auto_mount
> cd ..
> done
$ for rl in $(seq 3 5); do
> cd rc${rl}.d
> ln -s ../init.d/auto_mount S25auto_mount
> cd ..
> done
Create the sysconfig directory that the script will use:
$ mkdir /etc/sysconfig/automount-config
Inside /etc/sysconfig/automount-config/, you'll create pairs of files for each
group of devices you wish to automount. The format of the files is as follows:
xxxx.auto:
MOUNTPOINT=/path/to/mountdir
TIMEOUT=999
xxxx.map:
MOUNTNAME -fstype=FSTYPE[,OPTIONS] :/path/to/device
MOUNTNAME -fstype=FSTYPE[,OPTIONS] :/path/to/device
DO NOT create the "MOUNTNAME" directory under the "MOUNTPOINT" yourself.
Automount will create and remove this directory as needed.
The format of the .auto files is arbitrarily determined by the workings of the
auto_mount script; more information on the format of the .map files can be
found using "man 5 autofs". The OPTIONS used in the .map file are the same
options you would pass to mount with the -o flag. Note that you can have
multiple entries in a .map file, but they will all assume the same mountpoint
and timeout specified in the corresponding .auto file of the same prefix. The
auto_mount script can handle any number of .map/.auto pairs (so long as the
pairs both have the same prefix). Here are some examples:
--
cdrom.auto:
MOUNTPOINT=/mnt
TIMEOUT=5
cdrom.map:
cd -fstype=iso9660,ro :/dev/cdrom
--
The above pair will automount /dev/cdrom at /mnt/cd with a timeout of 5
seconds. This means that after five seconds of inactivity the cdrom device will
be automatically unmounted, allowing you to put in a new CD to be automatically
remounted upon subsequent access. You can verify this after initializing
automount:
$ ls /mnt/cd; mount
You will see that the cdrom is mounted. Wait five seconds.
$ mount
If everything is working properly, automount will have unmounted the cdrom.
Subsequent access to /mnt/cd will cause it to be remounted.
Most CD drives lock their CD trays while mounted, preventing you from removing
the media while the drive is mounted. Floppy drives, on the other hand, have
no such protection; it is best to keep their timeout value as small as possible:
--
floppy.auto:
MOUNTPOINT=/mnt
TIMEOUT=1
floppy.map:
flop -fstype=auto :/dev/fd0
--
This mounts the floppy drive at /mnt/flop. Note that a timeout of 0 will
disable the automatic unmounting altogether.
Automount can also be used to mount network shares:
--
samba.auto:
MOUNTPOINT=/smb/win2kbox
TIMEOUT=300
samba.map:
c -fstype=smbfs,username=samba,password=xxxx ://win2kbox/c
d -fstype=smbfs,username=samba,password=xxxx ://win2kbox/d
--
The two samba shares specified will be automounted at /smb/win2kbox/c and
/smb/win2kbox/d
One final note of caution (from the autofs man page):
UNSUPPORTED:
The automounter does not support direct maps or mount
trees (more than one file system to be mounted under a spe-
cific automount point)...
This (unfortunately) means that you can't have separate
.auto/.map pairs with the same MOUNTPOINT. Thus, the individual
floppy and cdrom examples used above cannot be used together! The
best alternative in this case is to combine them into one file pair:
--
removables.auto:
MOUNTPOINT=/mnt
TIMEOUT=1
removable.map:
cd -fstype=iso9660,ro :/dev/cdrom
flop -fstype=auto :/dev/fd0
--
The more adventurous among you may also consider compiling and
installing automount v4 (beta). Its compilation and installation
is virtually identical to that outlined above, with the
exception of the patching of lookup_module.c (the first block of
commands). Upgrading is as simple as:
$ tar xvfj autofs-4.0.0pre10.tar.bz2
$ cd autofs-4.0.0pre10
$ ./configure --prefix=/usr --sbindir=/sbin && make &&
make install
$ /etc/rc.d/init.d/auto_mount restart
Feel free to e-mail me with questions or suggestions.