Manage remote Linux servers and workstations with ease

No matter how hard you try, you can't be everywhere at once. Servers and workstations that you need to support can be based in various locations, sometimes even thousands of miles away. Physical access to these systems on short notice is impossible. Fortunately, there are several widely used remote administration methods for Linux that let you cross that distance in little more than a few mouse clicks. Here are four major Linux remote administration utilities and some pluses and minuses for each.

Using Secure Shell
Secure Shell (SSH) is probably the most popular remote administration tool. SSH offers command line access over an encrypted tunnel. Many Linux distributions come with an SSH server already installed. As with any tool, patches must be installed and restrictions should be put in place to keep unauthorised users from using the service.

Once you have an SSH server installed, configuring it is fairly easy. There are a couple of major settings that you should have in place to minimise risk, including:

• PermitRootLoginâ€"This value should be set to No, since root should never log in remotely. If you want to administer the box, create a normal user and SSH in with that account. Once in, you can use the su command to log in as root.
• X11 Forwardingâ€"This value will be used for getting a graphical connection. If you just want to use the console, you can set this value to No; otherwise, set it to Yes.

If you don't have an SSH server installed, you can use your Linux distribution's RPM installer to get it up and running. Once you've accomplished that, connecting is fairly simple. First, you need to obtain a client. My favorite free SSH client is PuTTY, which you can download from the PuTTY Web site. PuTTY is a great little utility that allows you to connect to remote systems using various protocols, including SSH and Telnet.

Configuring PuTTY is very easy. To connect to a remote system, all you have to do is fill in the host name or IP address to connect to, and select SSH for the connection type, as shown in Figure A.

Figure A

Configuring PuTTY for SSH

Once you connect to the remote system, you have full shell access allowing you to issue commands as you would from the console.

Using Telnet
Telnet, much like SSH, allows for remote console-level access to a system. The major difference between these two is that Telnet is not encrypted, meaning it is open for all to see. Most major Linux distributions come with a Telnet package that can be installed, but is not by default.

You can install a Telnet daemon using your distribution's RPM installer. Because of the inherent insecurity in using an unencrypted connection, most distributions have the Telnet service disabled. Most Telnet daemons run through Xinetd, a management system for services. To enable a Telnet daemon that runs through Xinetd, edit the /etc/xinetd.d/telnet file and change the value for Disable to No. Then, type service xinetd restart to have the changes take effect.

Connecting to a server with Telnet is even easier than with SSH. Nearly every operating system has a built-in Telnet client, including such obscure operating systems as OS/2. If you prefer, you can still use PuTTY and just select Telnet instead of SSH. To connect using the built-in Windows client, use the Run dialog box from the Start menu, as shown in Figure B.

Figure B

Running the Windows Telnet client

Once connected, you'll be presented with a standard logon prompt. You can remotely manage your system from the console, as you can with SSH.