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We've talked about using TAR Files and other forms of backups to backup files to the local system or to separate media but what you really need to do as a network administrator and as a UNIX system administrator is begin to backup files and transfer them across the network to file servers or other servers that are there to backup your files from your box. Those things are easy to do and you can use TAR as well as simply sending files across the network but you also need to learn how to do this with other tools as well. FTP and other file transfer tools can be used but keep in mind that they're probably not very secure. In fact, they're unencrypted so your backups run the risk of being intercepted by a malicious party. Secure Shell, which we'll talk about a little bit later on in the course, is a much better option to use. Secure Shell basically offers encrypted sessions to push files between two boxes over a network and you can also use Secure Shell to perform remote administration across the network. Secure Shell has several tools built in such as Secure FTP and Secure Copy. Either one of those is a much better way to transfer backup files to a network share over the secure connection. Now, two other tools that we'll talk about as well briefly are RSync and Unison. Now, RSync is a command that's basically designed to help with backups. RSync has a lot of features to it and basically it works across the network. It doesn't just move entire files. It also looks at file sizes and runs checksums on these file and compares local and remote files to each other and backs up only the blocks, the parts of the files that are different. So basically synchronizes backed-up files. Another tool that we'll mention briefly is Unison. Now, where RSync works only with one machine basically backing up one file from the machine or several files from one machine to a central network server and checking to see if they've been changed and backing up the changes, Unison can work with multiple machines. Let's say you have documents that are shared on multiple boxes and you need to be able to keep all copies of those documents in sync with each other. That's where Unison comes in. The good thing about Unison is even though it's a, basically a UNIX tool, it can work across platforms. It can work with BSD and if you have other boxes on the network, such as Windows or Linux, it can work with those too as well. One good thing about Unison and RSynch is they both can be used over Secure Shell connections for security. By themselves they don't offer a lot of security so you still run the risk of sending unencrypted data over the network where it can intercepted by possibly malicious third parties. So you can use both of these tools in conjunction with Secure Shell. Now, we'll cover Secure Shell a little bit later on in the course when we talk about security and we'll actually get to see Secure Copy and Secure FTP in action.