# Linux Autofs #

(July 2017)

Autofs automatically mounts filesystems on an as-needed basis.
Automounting network filesystems can be more performant and resilient than mounting them in fstab.

The `autofs` program controls `automount` daemons.
One `automount` daemon spaws for each map.

	# apt-get install autofs

(If mounting SMB shares, install the `samba` and `cifs-utils` packages too.)

Configure autofs using the `/etc/auto.*` config files.
Each line in the `/etc/auto.master` file matches a local mount-point with its map file, like:

	# mount-point [map-type[,format]:] map [options]
	/smb    /etc/auto.smb

Maps can be "direct" or "indirect".
The example above is an indirect map, because it tells autofs to create mount-points as *subdirectories* of `/smb`.
Direct maps create a mount-point *at* the path specified (not below it).
The mount-point entry in auto.master is always "/-".
For example, the following line instructs autofs to create a mount-point at the place specified in `/etc/auto.foo`:

	/-    /etc/auto.foo

Map files look like:

	# key [-options] location
	user1 -type=nfs  myserver:/home/user1
	mycifs -fstype=cifs,rw,uid=myuserid,gid=mygrpid ://example.com/sharename
	backup -fstype=cifs,rw,file_mode=0600,dir_mode=0700,nounix,uid=0,gid=0,forceuid,forcegid,credentials=/root/etc/autofs-secret-storage-backup.txt ://storage.example.com/linux_backups
	myssh -fstype=fuse,allow_other :sshfs\#user@example.com\:/path/to/mount
	tunes -fstype=ext4 :/dev/sda4

(Escape map locations beginning with "/" with a colon ":".)

For an indirect mount, the "key" can be a single directory name (as shown above).
For a direct mount, it should be the full path of the mount point.

## Debugging Auto Mount Problems ##

1. Stop the autofs daemon:

	# systemctl stop autofs

2. Run automount in the foreground:

	# automount -f -v

3. Test by cd'ing (or whatever) into the mount point.

## Links ##

- https://help.ubuntu.com/community/Autofs
- https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Storage_Administration_Guide/s2-nfs-config-autofs.html
- https://wiki.archlinux.org/index.php/autofs
- AUTO.MASTER(5)
- AUTOFS(5)
- AUTOFS(8)
- https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Storage_Administration_Guide/nfs-autofs.html