How can I unmount a s3fs mount as a normal user?

Question

I use S3 a ton. I have over 40 or so buckets floating around between clients. I like the fact that I can list them in /etc/fstab and that they just work. For reference here is one of the buckets.

coteyrnet /mnt/S3/coteyrnet fuse.s3fs _netdev,use_cache=/tmp,use_rrs=1,allow_other,noauto,users 0 0

It mounts fine, but I am having one heck of a time unmounting it.

The first problem is:

umount: /mnt/S3/coteyrnet mount disagrees with the fstab

The relevant part of mtab is:

s3fs /mnt/S3/coteyrnet fuse.s3fs rw,noexec,nosuid,nodev,allow_other,user=coteyr 0 0

When running mount with no arguments it reports the mount as:

s3fs on /mnt/S3/coteyrnet type fuse.s3fs (rw,noexec,nosuid,nodev,allow_other,user=coteyr)

In addition to that, if I sudo umount /mnt/S3/coteyrnet I always get

umount: /mnt/S3/coteyrnet: device is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))

lsof | grep coteyrnet never returns anything of value, nor does fuser.

My goal is to get user unmounting working.

The inability to mount via sudo has been resolved. By using the "use_cache" setting the files were actually open, but not under the mount point. This is a caveat to that option. The mount point files are closed but the files were not yet transferred to S3. By waiting "a while" and trying again, sudo can unmount.

Answer 1

After working with dpb, we have determined that the issue is a bug and not a lack of knowledge or configuration (it can't be fixed by us)

Issue 309 has been filed with s3fs maintainers.

Answer 2

I think /etc/fstab needs the option user. Right now you said you have:

s3fs /mnt/S3/coteyrnet fuse.s3fs rw,noexec,nosuid,nodev,allow_other,user=coteyr 0 0

Trying changing that user=coteyr to just user. That works for me. When I tried to specify the user with =, it was essentially ignored.

See the following output for an example:

dpb@helo:crash$ mount /mnt/foo
dpb@helo:crash$ umount /mnt/foo
dpb@helo:crash$ grep /mnt/foo /etc/fstab
/dev/vgdata/lvol0 /mnt/foo ext4 defaults,user 0 2
dpb@helo:crash$

Alternate Solution

If this fails, or if you want an alternate approach. You can set up a sudo rule that allows mounting and unmounting without a password for certain mounts. Some would claim this is a safer approach, but I'm no security guru.

More specifics for fuse.s3fs

It appears for umount as a non superuser to succeed, it needs to match what is shown by the mount command.

In this case, fstab would need to look like

s3fs   /mnt/S3/coteyrnet  fuse.s3fs  <options> 0 0

But, I think you still need a way to specify your unique bucket. Perhaps try:

s3fs#coteyrnet  /mnt/S3/coteyrnet  fuse.s3fs  <options> 0 0

That may be enough to trick mount (I've seen that before in a couple places, and now I'm starting to realize why)