NFS Services Administrator's Guide (B.11.31.04) March 2009

To configure multiple replicated servers for a directory, follow these steps:
1. Create and configure the /etc/netmasks file. AutoFS requires the
/etc/netmasks file to determine the subnets of local clients in a replicated
multiple server environment.
The /etc/netmasks file contains IP address masks with IP network numbers.
It supports both standard subnetting as specified in RFC-950, and variable-length
subnetting as specified in RFC-1519. For standard subnetting, the file must contain
a single line for each network. This provides the network number and the network
mask to be used on that network. Specify the network number and the mask using
the conventional IP dot (.) notation. The network number must be either a class
A, B, or C network number. For example:
network number netmask
128.32.0.0 255.255.255.0
For variable length subnetting, the /etc/netmasks file must contain a line for
each subnet, where the first field refers to the subnet and the second field refers
to the netmask. The format for specifying these fields is the same as that of standard
subnetting.
Example of using the /etc/netmasks File
The following example shows how AutoFS uses the /etc/netmasks file to determine
the local client subnets in a multiple-server environment. In this example, servers basil
and thyme export/nfs/mount. The IP address for server basil is 15.43.232.30, and
the IP address for the server, thyme is 15.244.10.20:
# /etc/auto_direct file
/nfs_mount basil,thyme:/nfs/mount
#/etc/netmasks file on the client sage:
#network number netmask
15.43.234.210 255.255.248.0
AutoFS uses the /etc/netmasks file to determine that the masked value for the subnet
of basil and the network number is the same (15. 42. 232. 0). This shows that the client
is on the same network as basil. AutoFS then mounts /nfs/mount from basil on
the local subnet.
Notes on Configuring Replicated Servers
Directories with multiple servers must be mounted as read-only to ensure that the
versions remain the same on all servers.
The server selected for the mount is the one with the highest preference, based on a
sorting order. The sorting order used gives highest preference to servers on the same
local subnet. Servers on the local network are given the second strongest preference.
As a result, if you configure multiple servers on both sides of a gateway, a server on
96 Configuring and Administering AutoFS