Configuring Autofs

Kyle Rankin

President of NBLUG

What is Autofs?

Autofs is a kernel option which allows you to automatically mount filesystems when you access them, and automatically unmount them when you are done using them.

So What?

Accessing a CD in Autofs

Big Deal, <foo> does that too

I like Autofs because it's:

• flexible--it can automatically mount any filesystem you can mount manually, including network shares
• simple--configuration file syntax is similar to fstab
• configurable--timeouts and other facets of filesystem mounting are completely configurable
• scriptable--any filesystem configuration file can be replaced by a script

Installing Autofs

1. Configure the kernel
2. Install Autofs software
3. Configure Autofs
4. Script Autofs (optional)

Configure the kernel

Install Autofs software

• Debian: apt-get install autofs
• Redhat/Fedora: use up2date, yum, apt4rpm, or rpm itself to install the autofs package
• Any other distribution: use the package manager to install the autofs package
• Worst case, no package, install from source: ftp://ftp.kernel.org/pub/linux/daemons/autofs/v4/

Configure Autofs

1. Create /etc/auto.master
2. Create /etc/auto.* files
3. Restart autofs
4. Access a configured directory

Creating /etc/auto.master

# Sample auto.master file
# Format of this file:
# mountpoint map options

/var/autofs/ejectable	/etc/auto.ejectable	--timeout=5

/var/autofs/usb	/etc/auto.usb	--timeout=2

/var/autofs/smb	/etc/auto.smb	--timeout=60

/var/autofs/smbbrowse	/etc/auto.smbbrowse	--timeout=60,-nonstrict

/var/autofs/ssh /usr/bin/auto.sshfs	uid=1000,gid=1000,--timeout=30

/var/autofs/ftp /usr/bin/auto.ftpfs     uid=1000,gid=1000,--timeout=30

Create /etc/auto.ejectable

# Format of file:
# mountpoint options device
cdrom	-fstype=iso9660,ro,sync,nodev,nosuid	:/dev/cdrom
floppy	-fstype=auto,sync,nodev,nosuid	:/dev/fd0

What this does

• Restart autofs with (distribution-specific):
/etc/init.d/autofs restart
• No specific mountpoints from auto.ejectable will appear until they are accessed, so
ls /var/autofs/ejectable/
will show nothing, until you
ls /var/autofs/ejectable/cdrom
(or access it some other way)

Log Output

(from command ls /var/autofs/ejectable/cdrom)

automount[17237]: attempting to mount entry 
/var/autofs/ejectable/cdrom
automount[3028]: lookup(file): looking up cdrom
automount[3028]: mount(generic): calling mkdir_path 
/var/autofs/ejectable/cdrom
automount[3028]: mount(generic): calling mount -t iso9660 
-s -o ro,sync,nodev,nosuid /dev/cdrom /var/autofs/ejectable/cdrom
automount[3044]: running expiration on path 
/var/autofs/ejectable/cdrom
automount[3044]: expired /var/autofs/ejectable/cdrom

Configure /etc/auto.master

# Sample auto.master file
# Format of this file:
# mountpoint map options

/var/autofs/ejectable		/etc/auto.ejectable	--timeout=5

/var/autofs/usb		/etc/auto.usb	--timeout=2

/var/autofs/smb		/etc/auto.smb	--timeout=60

/var/autofs/smbbrowse	/etc/auto.smbbrowse	--timeout=60,-nonstrict

/var/autofs/ssh /usr/bin/auto.sshfs     uid=1000,gid=1000,--timeout=30

/var/autofs/ftp /usr/bin/auto.ftpfs     uid=1000,gid=1000,--timeout=30

Create /etc/auto.usb

# Format of file:
# mountpoint options device
sda     -fstype=vfat,uid=1002,gid=1002,umask=002,noatime        :/dev/sda1
sdb     -fstype=vfat,uid=1002,gid=1002,umask=002,noatime        :/dev/sdb1
sdc     -fstype=vfat,uid=1002,gid=1002,umask=002,noatime        :/dev/sdc1
sdd     -fstype=vfat,uid=1002,gid=1002,umask=002,noatime        :/dev/sdd1

Configure /etc/auto.master

# Sample auto.master file
# Format of this file:
# mountpoint map options

/var/autofs/ejectable	/etc/auto.ejectable	--timeout=5

/var/autofs/usb	/etc/auto.usb	--timeout=2

/var/autofs/smb	/etc/auto.smb	--timeout=60

/var/autofs/smbbrowse	/etc/auto.smbbrowse	--timeout=60,-nonstrict

/var/autofs/ssh /usr/bin/auto.sshfs     uid=1000,gid=1000,--timeout=30

/var/autofs/ftp /usr/bin/auto.ftpfs     uid=1000,gid=1000,--timeout=30

Create /etc/auto.smb

# Format of file:
# mountpoint options device
backup  -fstype=smbfs,username=joey,password=god,uid=1000,gid=1000
	://gibson/backup
html    -fstype=smbfs,username=joey,password=god,uid=1000,gid=1000
	://gibson/html
mp3     -fstype=smbfs,username=joey,password=god,uid=1000,gid=1000
	://gibson/mp3

Introduction to Lufs

Lufs:
• Is a special experimental filesystem option that can be built against your current kernel.
• Lets you mount remote FTP and SSH servers as though they were SMB of NFS mountpoints.

Installing Lufs (briefly)

• Download Lufs source and build against your current kernel
• Download and install the Lufs utilities, which include special programs to mount FTP and SSH mountpoints, along with included scripts for use with autofs

Configure auto.master

# Sample auto.master file
# Format of this file:
# mountpoint map options

/var/autofs/ejectable	/etc/auto.ejectable	--timeout=5

/var/autofs/usb	/etc/auto.usb	--timeout=2

/var/autofs/smb	/etc/auto.smb	--timeout=60

/var/autofs/smbbrowse	/etc/auto.smbbrowse	--timeout=60,-nonstrict

# THESE LINES
/var/autofs/ssh /usr/bin/auto.sshfs     uid=1000,gid=1000,--timeout=30

/var/autofs/ftp /usr/bin/auto.ftpfs     uid=1000,gid=1000,--timeout=30

Configuring auto.ftpfs

• You don't. /usr/bin/auto.ftpfs is a script!
• auto.ftpfs dynamically creates autofs configurations based on where you navigate in the filesystem
• auto.ftpfs defaults to a guest account, but can accept browsing to /var/autofs/ftp/user:pass@host

Using auto.ftpfs

clover:~# ls /var/autofs/ftp/
(no output)
clover:~# ls /var/autofs/ftp/ftp.kernel.org/pub/linux/kernel/
COPYING   README       people    testing  v1.1  v2.0  v2.3  v2.6
CREDITS   SillySounds  ports     uemacs   v1.2  v2.1  v2.4
Historic  crypto       projects  v1.0     v1.3  v2.2  v2.5
clover:~# ls /var/autofs/ftp/
ftp.kernel.org

Writing Autofs scripts

What does an Autofs script do?

Basically, Autofs scripts are passed directory names and output a configuration based on the directory name.

Could be as simple as a bash script that echoes a default configuration (but that's really no different from having a static config file) or as complicated as you want to make it.

My Autofs script--auto.smbbrowse

• Problem: I wanted to be able to dynamically browse guest SMB shares like I could with guest FTP shares under Lufs
• Solution: Write a Perl script that gets passed an SMB server, and scans that server for guest shares, outputting the Autofs configuration for any guest shares it finds

Testing auto.smbbrowse

(in this example, gibson happens to be an SMB server on the network)

greenfly@clover:~$ /etc/auto.smbbrowse gibson 
-fstype=smbfs,guest     /mp3 //gibson/mp3	/print$ //gibson/print$

Configure auto.master

# Sample auto.master file
# Format of this file:
# mountpoint map options

/var/autofs/ejectable	/etc/auto.ejectable	--timeout=5

/var/autofs/usb	/etc/auto.usb	--timeout=2

/var/autofs/smb	/etc/auto.smb	--timeout=60

# THIS LINE
/var/autofs/smbbrowse	/etc/auto.smbbrowse	--timeout=60,-nonstrict

/var/autofs/ssh /usr/bin/auto.sshfs     uid=1000,gid=1000,--timeout=30

/var/autofs/ftp /usr/bin/auto.ftpfs     uid=1000,gid=1000,--timeout=30

auto.smbbrowse in action

greenfly@clover:~$ ls /var/autofs/smbbrowse
(no output)
greenfly@clover:~$ ls /var/autofs/smbbrowse/gibson
mp3
greenfly@clover:~$ ls /var/autofs/smbbrowse/gibson/mp3
311                                    nofx
Reef Madness!                          offspring
Surf Rider                             operation_ivy
anti-flag                              pennywise
...
nin                                    various_artists

Managing Autofs mountpoints

Use symlinks

• Gives you a directory to browse to at all times
• Still doesn't mount until you access inside the directory
• Allows you to get directly to a section of the filesystem you are interested in, like:
/mnt/kernel -> /var/autofs/ftp/ftp.kernel.org/pub/linux/kernel

Managing Autofs mountpoints (cont.)

• Organize mountpoints according to type
• All SMB mountpoints together, all NFS together, etc.
• Use hotplug to create symlinks when drives are inserted, delete symlinks when drives are removed

Autofs problems

• FAM
• Often used by Konqueror, Nautilus, to poll filesystems for changes
• Its constant polling means autofs filesystems may not time out
• Removable drives
• Doesn't 100% protect you from removing a drive prematurely
• Use a short timeout (1-2 seconds) when possible

Questions?

This presentation is adapted from my tips page at http://www.greenfly.org/tips/autofs.html