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(am-utils.info)Home Directories

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Home Directories
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   One convention for home directories is to locate them in `/homes' so
user `jsp''s home directory is `/homes/jsp'.  With more than a single
fileserver it is convenient to spread user files across several
machines.  All that is required is a mount-map which converts login
names to an automounted directory.

   Such a map might be started by the command:

     amd /homes amd.homes

   where the map `amd.homes' contained the entries:

     /defaults   type:=link   # All the entries are of type:=link
     jsp         fs:=/home/charm/jsp
     njw         fs:=/home/dylan/dk5/njw
     ...
     phjk        fs:=/home/toytown/ai/phjk
     sjv         fs:=/home/ganymede/sjv

   Whenever a login name is accessed in `/homes' a symbolic link
appears pointing to the real location of that user's home directory.  In
this example, `/homes/jsp' would appear to be a symbolic link pointing
to `/home/charm/jsp'.  Of course, `/home' would also be an automount
point.

   This system causes an extra level of symbolic links to be used.
Although that turns out to be relatively inexpensive, an alternative is
to directly mount the required filesystems in the `/homes' map.  The
required map is simple, but long, and its creation is best automated.
The entry for `jsp' could be:

     jsp   -sublink:=${key};rfs:=/home/charm \
                    host==charm;type:=ufs;dev:=/dev/xd0g \
                    host!=charm;type:=nfs;rhost:=charm

   This map can become quite big if it contains a large number of
entries.  By combining two other features of Amd it can be greatly
simplified.

   First the UFS partitions should be mounted under the control of
`/etc/fstab', taking care that they are mounted in the same place that
Amd would have automounted them.  In most cases this would be something
like `/a/"host"/home/"host"' and `/etc/fstab' on host `charm' would
have a line:

     /dev/xy0g /a/charm/home/charm 4.2 rw,nosuid,grpid 1 5

   The map can then be changed to:

     /defaults    type:=nfs;sublink:=${key};opts:=rw,intr,nosuid,grpid
     jsp          rhost:=charm;rfs:=/home/charm
     njw          rhost:=dylan;rfs:=/home/dylan/dk5
     ...
     phjk         rhost:=toytown;rfs:=/home/toytown;sublink:=ai/${key}
     sjv          rhost:=ganymede;rfs:=/home/ganymede

   This map operates as usual on a remote machine (ie `${host}' not
equal to `${rhost}').  On the machine where the filesystem is stored
(ie `${host}' equal to `${rhost}'), Amd will construct a local
filesystem mount point which corresponds to the name of the locally
mounted UFS partition.  If Amd is started with the `-r' option then
instead of attempting an NFS mount, Amd will simply inherit the UFS
mount (Note: Inheritance Filesystem).  If `-r' is not used then a
loopback NFS mount will be made.  This type of mount is known to cause
a deadlock on many systems.