macOS Big Sur 11.0.1 upgrade preserves auto_master customizations

The upgrade process to macOS Big Sur 11.0.1 preserves your custom automount master mapping (auto_master) file. This is a welcome improvement over Catalina, and eliminates the need to manually restore your auto_master changes after the upgrade.

This post is a follow-up to my previous coverage of macOS Catalina 10.15.x auto_master resets after upgrade.

I recently upgraded my MacBook Pro from Catalina 10.15.7 to Big Sur 11.0.1 and was delighted to find that my automounts still work post-upgrade! As a frequent user of network shares on my home network, I have to commend the folks at Apple for *finally* getting this one right.

Following a successful upgrade, check the automount master mapping file (/etc/auto_master) to verify that your previously-working changes were preserved.

sudo nano /etc/auto_master

As a refresher, the default contents of the master mapping file look something like this:

#
# Automounter master map
#
+auto_master            # Use directory service
#/net                   -hosts          -nobrowse,hidefromfinder,nosuid
/home                   auto_home       -nobrowse,hidefromfinder
/Network/Servers        -fstab
/-                      -static

In my case, I have one line appended which references my other auto_nas file. (You may have more than one, depending on your setup.)

/-                      auto_nas

For manual verification, you can run the automount command to flush the cache and reload /etc/auto_master:

sudo automount -vc

Look for confirmation that each share mounted successfully:

automount: /System/Volumes/Data/Nas/media mounted
automount: /System/Volumes/Data/Nas/storage mounted
automount: /System/Volumes/Data/Nas/archives mounted

Assuming you upgraded from Catalina, you have likely already ensured that your mountpoints are updated to match Catalina’s new directory structure. Otherwise, automount will complain about the mount point not existing.

Happy automounting!

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