Lion & Automounter

Mounting a remote filesystem via the network is something which Unix has been doing since, well, the dawn of Unix. So, naturally, when trying to make use of large amounts of network storage on a NAS from a Mac OS X based machine, one would assume that mounting the network storage and having the mountpoint be maintained automatically should be a simple Unix configuration. And there you’d be partly correct…

Darwin does make use of the automount system to configure and maintain mountpoints, and one can setup entries in the /etc/fstab to mount remote filesystems using various protocols (NFS, SMB, AFP, etc.), and various posts about doing this have been around for a long time . However, Mac OSX Lion seems to have broken this in such a way that the mount points are inaccessible (incorrect permissions) to all but the root user.

Over the weekend I struggled with this for too long, and ultimately found a solution, albeit a bit of a hack. Roll up your sleeves, get a new cup of tea, here we go…

/etc/fstab

As root, edit your /etc/fstab and add the mount point you want. Note: /etc/fstab did not exist by default. No need to worry, just create it. The magic syntax is:

<servername>:/<path> <mount_point> url auto,url==afp://<username>:<password>@<servername>/<path> 0 0

Example:

nas.grokers.net:/media /Network/media url auto,url==afp://levi:foopass@nas.grokers.net/media 0 0

That sets up a mount point at /Network/media which points to the AFP share nas.grokers.net/media

If you do this, then tell automount to reload with automount -cv you’ll be able to cd into /Network/media and see the remote filesystem, but only as root (in Lion, at least).

As an aside, it pains me to embed a password in the filesystem like this. A long time ago, I spent a lot of effort trying to figure out a way to dynamically load the password from the Keychain instead of embedding it here. I researched how to use executable automount configurations so I could fetch the password using /usr/bin/security but ultimately could never get it to work, so I gave up. If you’ve a way to do this, please let me know.

root-only permissions work-around

To avoid the root-only permissions on the mount point, it would appear a solution is to unmount the mountpoint after automount loads the configuration in /etc/fstab.

I tried many different approaches to unmount the mountpoint using a launchd /Library/LaunchAgent and even a user LaunchAgent, but through many attempts none of them seemed to take place after automount had loaded the config, and thus the mountpoint was still root-only accessible.

So, an AppleScript application as a Login Item seems to be the only way, but we don’t have to embed our password (yet again) in the applescript. Instead, I created a shell script to do the deed:

#!/bin/bash
diskutil unmount /Network/media > /dev/null 2>&1
exit 0

(I saved it at /Users/levi/Library/Automation/nas_mount_helper.sh but it doesn’t matter where you put it)

Then add a line to the sudoers file so the script will run as root without the need for a password:

$ sudo visudo

levi ALL = NOPASSWD: /Users/levi/Library/Automation/nas_mount_helper.sh

Now, to run this script as a Login Item, I created an AppleScript application using the AppleScript editor app. The contents of the applescript is pretty basic:

do shell script "sudo /Users/levi/Library/Automation/nas_mount_helper.sh"

Save the script as an application, and use the “Users & Groups” System Preferences to add it as a Login Item

Almost there…

Unfortunately, this didn’t quite do it. Upon login the mount couldn’t be navigated to via the Finder because of some error about the original not being found, so…

Another shell script was needed to force the mount.

#!/bin/bash
cd /Network/media
ls -la
exit 0

(I saved it at /Users/levi/Library/Automation/nas_mount_helper2.sh but it doesn’t matter where you put it)

This one we want to run as ourself, so no sudoers entry is needed.

Add an additional line to the applescript to run this after we unmount the share:

do shell script "sudo /Users/levi/Library/Automation/nas_mount_helper.sh"
do shell script "/Users/levi/Library/Automation/nas_mount_helper2.sh"

Extra Credit

Finally, to prevent the AppleScript application from being noticeable (showing up in the dock, etc.), add the LSUIElement key to the Info.plist of the generated AppleScript application, by contextually clicking on the app from the Finder, choosing “Show Package Contents”, browse to Contents/Info.plist, and then edit the Info.plist to add the element:

<plist version="1.0">
  <dict>
    ...
    <key>LSUIElement</key>
    <string>1</string>
    ...
  </dict>
</plist>

Not all that elegant, unfortunately, but a workaround at least.

Thanks

Thanks to @signed8bit for the moral support, and the wayback-machine.
Thanks to Soli for the unmount workaround idea.

Comments

Max Yarchak

I face the same issue. I’ve build a script which does reconnect to wifi (network) and it solves the issue with permissions for me.
https://github.com/MaxProWeb/MacAutomountFix