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(am-utils.info)User Filesystems

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User Filesystems
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   With more than one fileserver, the directories most frequently
cross-mounted are those containing user home directories.  A common
convention used at Imperial College is to mount the user disks under
/home/machine.

   Typically, the `/etc/fstab' file contained a long list of entries
such as:

     machine:/home/machine /home/machine nfs ...

   for each fileserver on the network.

   There are numerous problems with this system.  The mount list can
become quite large and some of the machines may be down when a system is
booted.  When a new fileserver is installed, `/etc/fstab' must be
updated on every machine, the mount directory created and the filesystem
mounted.

   In many environments most people use the same few workstations, but
it is convenient to go to a colleague's machine and access your own
files.  When a server goes down, it can cause a process on a client
machine to hang.  By minimizing the mounted filesystems to only include
those actively being used, there is less chance that a filesystem will
be mounted when a server goes down.

   The following is a short extract from a map taken from a research
fileserver at Imperial College.

   Note the entry for `localhost' which is used for users such as the
operator (`opr') who have a home directory on most machine as
`/home/localhost/opr'.

     /defaults       opts:=rw,intr,grpid,nosuid
     charm           host!=${key};type:=nfs;rhost:=${key};rfs:=/home/${key} \
                     host==${key};type:=ufs;dev:=/dev/xd0g
     #
     ...
     
     #
     localhost       type:=link;fs:=${host}
     ...
     #
     # dylan has two user disks so have a
     # top directory in which to mount them.
     #
     dylan           type:=auto;fs:=${map};pref:=${key}/
     #
     dylan/dk2       host!=dylan;type:=nfs;rhost:=dylan;rfs:=/home/${key} \
                     host==dylan;type:=ufs;dev:=/dev/dsk/2s0
     #
     dylan/dk5       host!=dylan;type:=nfs;rhost:=dylan;rfs:=/home/${key} \
                     host==dylan;type:=ufs;dev:=/dev/dsk/5s0
     ...
     #
     toytown         host!=${key};type:=nfs;rhost:=${key};rfs:=/home/${key} \
                     host==${key};type:=ufs;dev:=/dev/xy1g
     ...
     #
     zebedee         host!=${key};type:=nfs;rhost:=${key};rfs:=/home/${key} \
                     host==${key};type:=ufs;dev:=/dev/dsk/1s0
     #
     # Just for access...
     #
     gould           type:=auto;fs:=${map};pref:=${key}/
     gould/staff     host!=gould;type:=nfs;rhost:=gould;rfs:=/home/${key}
     #
     gummo           host!=${key};type:=nfs;rhost:=${key};rfs:=/home/${key}
     ...

   This map is shared by most of the machines listed so on those
systems any of the user disks is accessible via a consistent name.  Amd
is started with the following command

     amd /home amd.home

   Note that when mounting a remote filesystem, the "automounted" mount
point is referenced, so that the filesystem will be mounted if it is
not yet (at the time the remote `mountd' obtains the file handle).