Now that you have your new Linux server up and running and are really ready to start working with it, you probably want to set up a network with your Unix server so that you can more easily share files. This will help you greatly in your efforts to migrate your Unix server to Linux and will also give you a better understanding of the networking challenges ahead.
If you have two systems, and you want to share data, the network should be your ultimate goal. Of course, you can data sharing tasks with tar and cpio and a functioning tape drive. With a network, however, you have more functionality at your fingertips. For example, you can set up NFS to mount files on your local box, which will let you copy files along at much faster speeds then you can get with a tape drive.
One of the first things you'll need to do is get together with your network team and find out some basic information. For instance, if you wish to install a Linux machine onto an existing IP network, then you should contact the network administrator and ask them for the following information; IP Address, broadcast address, subnet address, default gateway and DNS Server (if you're using DNS).
In the past, you could set up your networks with linuxconf, but this tool is no longer available on most Linux distros. So, use the command line or other GUI-type tools available in your distribution. For example, ifconfig is a command that you definitely should know about. This example configures your
/sbin/ifconfig eth0 192.168.8.122 netmask 255.255.255.0 broadcast 192.168.8.255
It's important to note that ifconfig on Linux does not store this information permanently. (Unix distros work similarly, by the way.) It will be lost after a reboot. What you can do is manually add the network command to the end of the /etc/rc.d/rc.local file. If this is a little too much for you, try using the netcfg, neat or netconfig commands to make the changes permanent. These utilities update files that reside in /etc/sysconfig/network-scripts/.
Netconfig is a console tool, while neat is a Gnome GUI admin tool. I like netconfig as it is very simple and does a lot of the work for you, though you should really also try to understand what is going on behind the scenes. Just understand that it won't have all the bells and whistles of netcfg and neat.
Red Hat tools store the configuration date in /etc/sysconfig/network and let you configure the routing information as well. As far as your routes are concerned, use the route command, which will configure the /etc/sysconfig/static-routes file. When you change your host name, you'll first have to issue the hostname command. For example, hostname linux1 will change your host to linux1. You'll also have to edit the /etc/sysconfig/network file with your new host name. Don't forget to reboot your box or restart any systems which need the prior hostname. Also, change the /etc/hosts file on this server and on your Unix server as well to reflect the new system name. After your Linux server is configured, first try pinging your Unix server. If you can, you have your network. If not, there's probably something you forgot to do. I would make sure your network information looks good, if only one digit is wrong in your IP address or default gateway, then that will throw everything out of whack.
I would also check to make sure the physical cabling is good. Try pinging your default gateway. If you can't get there, you're not going to get to your Unix server, either. Run diagnostics to make sure your NIC card is okay. Ping your loopback address. It may take some time, but it will be well worth the effort. Though setting up a network in some cases can be much more difficult than copying files back and forth from tapes, in the long run, you will be glad you did!
This was first published in December 2004