Using Compression Tools

Compression is an important aspect of working with backup files. It takes less disk space on your backup medium (CD, DVD, tape, and so on) or server to store compressed files. It also takes less time to transfer the archives to the media or download the files over a network. While compression can save a lot of storage space and transfer times, it can significantly increase your CPU usage. You can consider using hardware compression on a tape drive (see www.amanda.org docs faq.html id34 6016)....

Configuring the BuiltIn Firewall

A firewall is a critical tool for keeping your computer safe from intruders over the Internet or other network. It can protect your computer by checking every packet of data that comes to your computer's network interfaces, then making a decision about what to do with that packet based on the parameters you set. The firewall facility built into the current Linux kernel is called iptables. (You may also hear of ipchains, which was iptables' predecessor in kernel 2.2 and below.) The iptables...

Chatting with Friends in IRC

Despite the emergence of instant messaging, Internet Relay Chat (IRC) is still used by a lot of people today. Freenode.net has tons of chat rooms dedicated to supporting major open source software projects. In fact, many people stay logged into them all day and just watch the discussions of their favorite Linux projects scroll by. This is known as lurking. The xchat utility is a good graphical, multi-operating system IRC client. From Fedora, select Applications O Internet O IRC. But the elite...

Using Dialup Modems

Although high-speed DSL, cable modem, and wireless LAN hardware have become widely available, there may still be times when a phone line and a modem are your only way to get on the Internet. Linux offers both graphical and command line tools for configuring and communicating with modems. As with other network connections in Fedora, dial-up modem connections can be configured using the Network Configuration window. Most external serial modems will work with Linux without any special...

Changing Permissions with chmod

The chmod command lets you change the access permissions of files and directories. Table 4-1 shows several chmod command lines and how access to the directory or file changes. Table 4-1 Changing Directory and File Access Permissions Table 4-1 Changing Directory and File Access Permissions The directory's owner can read or write files in that directory as well as change to it. All other users (except root) have no access. Same as for owner. All others can change to the directory, but not view or...

Using Named Pipes and Sockets

When you want to allow one process to send information to another process, you can simply pipe ( ) the output from one to the input of the other. However, to provide a presence in the file system from which a process can communicate with other processes, you can create named pipes or sockets. Named pipes are typically used for interprocess communication on the local system, while sockets can be used for processes to communicate over a network. Named pipes and sockets are often set up by...

Working with Users and Groups

During most Linux installation procedures, you are asked to assign a password to the root user (for system administration). Then you might be asked to create a user name of your choice and assign a password to that as well (for everyday computer use). We encourage you to always log in as a regular user and only su or sudo to the root account when necessary. When Linux is installed, you can use commands or graphical tools to add more users, modify user accounts, and assign and change passwords....

Using Text Based Email Clients

Most Mail User Agents (MUAs) are GUI-based these days. So if you began using e-mail in the past decade or so, you probably think of Evolution, Kmail, Thunderbird, or (on Windows systems) Outlook when it comes to e-mail clients. On the first Unix and Linux systems, however, e-mail was handled by text-based applications. If you find yourself needing to check e-mail on a remote server or other text-based environment, venerable text-based mail clients are available and still quite useful. In fact,...

Changing Running Processes

Even after a process is running, you can change its behavior in different ways. With the renice command, shown earlier, you can adjust a running process's priority in your system's scheduler. With the nice command, you can determine the default priority and also set a higher or lower priority at the time you launch a process. Another way you can change how a running process behaves is to send a signal to that process. The kill and killall commands can be used to send signals to running...