Side effects

The automounter has several side effects that cause confusion in both processes and users that encounter its emulated directories. This section uncovers some utilities that are disturbed by the automounter.

Long search paths

If you have many directories listed in your search path, logging into a system using the automounter for some of these directories increases your login time significantly. Instead of listing the directories in your search path, create "wrappers" for the utilities of interest and put them in /usr/local/bin. The wrappers can set environment variables and execute the appropriate utility, causing the automounter to mount the necessary filesystem when you use it instead of when you log in. For example, you can include Frame 6.0 in your search path in your cshrc file:

set path = ( /tools/deskset/frame6.0/bin $path )

If /tools is managed by the automounter, your shell causes /tools/deskset to be mounted when it builds the command hash table after setting your search path. Instead of listing all directories in /tools, create a wrapper in /usr/local/bin for the maker utility in /tools/deskset/frame6.0/bin so that you don't have to list any subdirectory of /tools in your search path:

Wrapper for maker  #!/bin/sh PATH=/tools/deskset/frame6.0/bin:$PATH exec /tools/deskset/frame6.0/bin/maker

This wrapper sets the search path as well, so that any executables invoked by maker will be able to find related utilities in its executable directory. By putting this wrapper in /usr/local/bin, you avoid having to automount /tools/frame6.0 when you log in. For just a few directories, the automounter overhead isn't that large, but with ten or more software packages loaded, logging in becomes a slow process. Furthermore, not mounting all of these filesystems when you log in shields you from server crashes: your workstation will only hang if one of the servers you're using crashes.

Avoiding automounted filesystems

Utilities run out of cron, such as nightly find jobs, are easily overworked by the automounter. The solution is to modify cron jobs to avoid remote filesystems:

Confine cron jobs to run find on local filesystems.
Use an option to find like -xdev or -mount to force find to not cross mount points.

This uses the above constraints to implement a script to search for core files:

mount | grep -v remote | awk ' {
 print $1
}
' | xargs -i find {} -name 'core*' - mount | /usr/bin/mailx -s"core file report" joe@eng

The mount invocation shows what is currently mounted, grep filters out anything that isn't local, awk prints the first argument (the mount points), xargs passes each mount point to a separate invocation of find, and find searches for files starting with the name core within the mount point's filesystem.