Hi,
I'm running AutoFS as distributed with debian (version 3.1.4-4) and was
intrigued by RMS's post to LKML
(http://kt.linuxcare.com/kernel-traffic/kt20000626_73.epl#3). I asked
him why AutoFS would not suffice and he basically said he didn't know
enough about it, but heard others say it was not. I was writing him
back and found that he's right. In order to have "DOS Style Floppy
Handling", I think AutoFS needs to be modified, and possibly the Linux
kernel as well.
The three things that DOS does that makes it easy for users is:
1) Auto-mount the floppy upon request
2) Write synchronously to the floppy
3) Auto-unmount upon ejection
AutoFS handles automounting (/var/autofs/misc/floppy under debian) but
not fully, because the floppy is always mounted as root, preventing the
user from using the floppy. This could be worked around by making the
floppy world writable, or creating a special 'diskette' group, but these
are cumbersome compared to what *should* be possible: UID
substitution. If we could specify "floppy -fstype=auto,sync,uid=$UID"
in auto.misc, condition 1 would be satisfied.
Condition 2 is satified by the "sync" option (which debian does not
include). Investigation and experimentation confirm that the option
"nosuid" MUST also be specified on all removable media. This is not an
AutoFS problem, but it should be WRITTEN IN BOLD in the documentation if
not already, and the man page should be updated to reflect this.
autofs(5) currently gives, as example,
floppy -fstype=auto :/dev/fd0
I *HIGHLY* recommend this be changed to the following:
floppy -fstype=auto,nosuid :/dev/fd0
with appropriate documentation to the danger of not including this
option on devices like floppy disks.
(This man page may not be part of the official AutoFS distribution;
Cc:ing author directly.)
Condition 3 needs a VFS hook, I believe. Yes, autofs will auto unmount
after a specific amount of time, but after ejecting the floppy, I can
still do a 'ls'. The buffer cache should be cleared when it is ejected,
and I believe the VFS gets this signal. It does when a CD-ROM is
inserted/ejected for sure. Even if I replace the floppy with another,
this cache remains intact, which is then just wrong.
Do these changes seem reasonable, and if a VFS change is required,
possible before the release of kernel 2.4?
sincerely,
Christopher W. Curtis
