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These posts are the creation of Doran L. Barton (AKA Fozziliny Moo). To learn more about Doran, check out his website at fozzilinymoo.org.

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Automounting Samba shares as a user with Fedora 16

Posted: 26 November 2011 at 23:47:28

It's been a while since I've blogged anything, let alone anything technical. So, here goes.

I've been making the rounds in our house, upgrading all the desktops to Fedora 16. For the most part, this has been fairly painless. One thing I've noticed, however, is that Fedora 16 changes the default UIDs for new users. In the past, UIDs started at 500. Now they start at 1000.

This became a problem when I tried to make changes to files on an NFS-mounted filesystem shared by a server running CentOS 5.7. On the CentOS server, my UID is 500. On my Fedora 16 desktop, my UID is 1000. I knew this was going to be a problem for other users in the house as well.

Ideally, some way of mounting NFS filesystems with some UID mapping would be the easiest approach here. I'm no NFS guru so I did some research online to see what I could come up with. I could be wrong, but this doesn't come easily.

So, next, I looked at using Samba instead of NFS. Because the various desktops might have more than one user account on them, I wanted to make sure each user could have access to files on the server they're supposed to have access to.

We use KDE on our desktops. KIO provides some very nice means for users to connect to network services via HTTP, SSH, SFTP, Samba, FTP, and other protocols. Once you connect to a network service, you can save the connection for use later. This is handy, but I could not find a way to make this work at the command-line as well. That is, if you have a Samba share mounted via KIO so you can access it via KDE applications, there is no way of opening a terminal application and interacting with the files in the Samba share with shell commands.

Right away, I got thinking this would really be a good use of Filesystem In Userspace FUSE. FUSE is a kernel module for Linux that allows non-privileged users to interact with the root filesystem aspects of the kernel. In addition to allowing non-root users to mount local devices and network services like Samba and SSH, it also has given way to some projects that do some very interesting things like provide filesystem access to archive files like .zip and .tar files.

It looks like there is a project called KioFuse that aims to make KIO connections available via FUSE, but I didn't see that until just now. In fact, I ran across this discussion on the KDE mailing list that seemed to indicate KIO and FUSE were not a match to be. It seems, however, that hasn't remained true. I will definitely have to check out KioFuse and see how well it performs.

Fedora 16 includes the fuse-smb package which provides FUSE access to Samba shares. On the surface, it appears to be fairly simple to use. You create a fusesmb.conf file in a .smb subdirectory in your home directory. This file should contain a username and password for the share you wish to mount. Then, create a directory to act as a mountpoint for the FUSE filesystem, like ~/Network. Finally, run fusesmb followed by the mount point you created.

fusesmb ~/Network

If all works well, you should be able to access servers and shares under your mountpoint. For example, ~/Network/servername/sharenamename.

I never got fuse-smb to work. I suspected SELinux was in the way, but I couldn't find any evidence to support that theory.

In the meantime, I've set up entries in /etc/fstab for the Samba share I want users to be able to access. The entry has the user option which allows a non-root user to control the mount. This provides some of what FUSE is supposed to do.

Next, I need the Samba share mounted for each user when they log in. To accomplish this, I created a simple shell script in the ~/.kde/Autostart directory that mounts the Samba share. Something like this:

#!/bin/bash

mount //server/share

Simple enough.

I also would like the system to automagically unmount the filesystem when the user logs out. To do this, I should be able to put a similar shell script in ~/.kde/shutdown that does a umount of the mounted filesystem. But, this didn't work.

Despite the fact the manual pages for mount and fstab clearly say all that is needed to allow normal users to mount and unmount a filesystem is to add the user option, I can't seem to unmount the Samba share as a non-root user.

$ umount /import/server/share 
umount: only root can unmount //server/share from /import/server/share

This is a partial solution. If others have ideas, I'm all ears. I'll continue to explore.

In the past, I had an OpenLDAP server that most of the desktops in the house authenticated against. When Fedora introduced SSSD, that stopped working and I had to create users on each desktop again. I'd like to eventually get back to that and I know that would solve the original problem with UID mapping.