Automounting with udev and pmount

For the past few years I was relying on a lengthy udev rules file to mount all the USB sticks and SD cards I put into my computer. Sometimes it mysteriously didn’t work, and each time I opened it to tweak something I gave myself a promise to rewrite it in a more maintainable way. Well, the day has come.

First of all, I checked out udisks, but it doesn’t suit my needs as it doesn’t handle stuff like proper mount options (each FS requires some unique mix of those) and disk labels (I don’t like figuring out whether /media/sdb is my USB pendrive or my player’s SD card). As for wrappers, none of those listed in Arch Wiki entry on udev are available in Debian Wheezy. It was quite obvious I have to write something of my own, again.

But I was lucky to come across the post by Martin Monperrus describing how to mount disks using pmount. His recipe didn’t work in all cases for me, though:

• pmount doesn’t handle disk labels by itself — I had to write something on top of it to pass the label as a parameter;
• my player couldn’t be mounted because right after plugging into the computer pmount failed, saying that no medium is present. The issue didn’t appear if I tried mounting not right away but a few seconds later, so I figured I need to insert some delay here;
• some files I work with have names with cyrillics in them, so disks should be mounted with UTF-8 encoding;
• just a detail: my Nook Simple Touch seems to arrange items in the library depending on the access time, so I had to specify --noatime option to preserve ordering between mounts.

After all the tweaking, I got this:

# We wrap commands into calls to /bin/sh because PROGRAM and RUN
# accept only single commands, not command lists.
# PROGRAM figures out the label of the disk. Caching only gets in a
# way, returning old labels instead of querying for new ones, so we
# disable it. We use sed to replace non-alphanumeric symbols with
# underscore to facilitate readability and "typeability".
# RUN mounts the disk with specified label.
ACTION=="add",    KERNEL=="sd[b-z]*", PROGRAM="/bin/sh -c '/bin/sleep 2; /sbin/blkid -c /dev/null -s LABEL -o value /dev/%k | /bin/sed -r s#[^a-zA-Z0-9-]#_#g'", RUN+="/bin/sh -c '/bin/sleep 3 ; /usr/bin/pmount --umask 000 --noatime --charset utf8 %k %c'"
ACTION=="remove", KERNEL=="sd[b-z]*", RUN+="/usr/bin/pumount %k"

# the same as above, but for memory cards
ACTION=="add",    KERNEL=="mmcblk*", PROGRAM="/bin/sh -c '/bin/sleep 3; /sbin/blkid -c /dev/null -s LABEL -o value /dev/%k | /bin/sed -r s#[^a-zA-Z0-9-]#_#g'", RUN+="/bin/sh -c '/bin/sleep 4 ; /usr/bin/pmount --umask 000 --noatime --charset utf8 %k %c'"
ACTION=="remove", KERNEL=="mmcblk*", RUN+="/usr/bin/pumount %k"

I won’t explain any of this as there’s a comment at the top of the code already. It all looks like a mess, but unfortunately there’s not much room for pretty formatting in udev rules. Anyway, it’s much better than what I had before, so (for now) I’m satisfied.

See you!

Update (01.04.2013): added --charset utf8 and a note about the option.