[Ovirt-devel] [PATCH server] verify hostname is not on the loopback entry in /etc/hosts

[David Lutterkort]

On Wed, 2009-03-25 at 15:21 -0400, Joey Boggs wrote: 
> +# verify hostname is not on the loopback line in /etc/hosts to prevent kerberos problems
> +hostname = `hostname`
> +hostsfile = File.new("/etc/hosts", "r")
> +while (line = hostsfile.gets)
> +     if line =~ /127.0.0.1/ && line.include?(hostname.chomp)
> +         if hostname !~ /localhost.localdomain/
> +         @cli.say("\nHostname must not be on the loopback 127.0.0.1 line in /etc/hosts")
> +         @cli.say("#{line}")
> +         exit(0)
> +         end
> +     end
> +end
> +hostsfile.close

This can produce false positives in a number of ways: (1) it will get
confused by comments:

        # We used to have, but that's wrong
        # 127.0.0.1 host.exmaple.com
        127.0.0.1 localhost.localdomain
        
It also gets confused if hostname is 'host.example.com' and the
127.0.0.1 line has an alias 'myhost.example.com'.

Finally, (but that should happen throughout the installer), the
installer shouldn't exit with status 0 when there was an error. It would
be good to have a convention like status == 0 when installer finished
successfully, status == 1 when an error happened, status == 2 when user
exited installer (e.g., by answering 'no' to some question)

A more robust implementation of the above would be:

        aug = Augeas::init(nil, nil, 0)
        hosts = "/files/etc/hosts/*"
        paths = aug.match("#{hosts}/canonical[../ipaddr = '127.0.0.1']") + 
                aug.match("#{hosts}/alias[../ipaddr = '127.0.0.1']")
        paths.each do |p|
          name = aug.get(p)
          if hostname == name
            @cli.say("\nHostname must not be on the loopback 127.0.0.1 line in /etc/hosts")
            if (prompt_yes_no("Should I fix that ?", :default => "n") == "y")
              aug.rm(p)
              aug.save
            end
          end
        end

David