The available status values on which we can act are:
- success
- notfound
- unavail
- tryagain
The requested entry was found without error. The default action for this status is return .
There was no error in the lookup, but the target host or network could not be found. The default action for this status is continue .
The service queried was unavailable. This could mean that the hosts or networks file was unreadable for the files service or that a name server or NIS server did not respond for the dns or nis services. The default action for this status is continue .
This status means the service is temporarily unavailable. For the files files service, this would usually indicate that the relevant file was locked by some process. For other services, it may mean the server was temporarily unable to accept connections. The default action for this status is continue .
A simple example of how you might use this mechanism is shown in Example 6-3 .
Example 6-3. Sample nsswitch.conf File Using an Action Statement
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# Information about this file is available in the 'libc6-doc' package.
hosts: dns [!UNAVAIL=return] files
networks: files
This example attempts host resolution using the Domain Name Service system. If the return status is anything other than unavailable, the resolver returns whatever it has found. If, and only if, the DNS lookup attempt returns an unavailable status, the resolver attempts to use the local /etc/hosts . This means that we should use the hosts file only if our name server is unavailable for some reason.
