4. System Administration

This section contains information on common system administration tasks. It is by no means an exhaustive list of what goes on in Linux system administration but rather a collection of a few common tasks that a new user may find useful. If you would like more information on Linux system administration, refer to the online Linux System Administrators' Guide, found at http://www.linuxdoc.org/LDP/sag/book1.html.

4.1. Changing your password

Every time you log onto a Linux system, you must provide a password for your account. Occasionally you may wish to change your password, and many systems require that you do so regularly for added security.

Changing your password is done in the Emacs shell. Normally, changing your password in the Emacs shell displays it on the screen and also speaks it aloud. However, Emacspeak adds a line to your .emacs file that keeps Emacs from echoing your password either visually or orally. Of course, it's still a good idea to change your password in a secure area where no-one is likely to watch you type it in. To change your password:

  1. From inside Emacs, type M-x shell to launch an Emacs shell.

  2. At the prompt, type passwd. You will be prompted for both your current password and your new password.

Note that some systems require passwords to be a certain length or contain certain characters such as numbers. If your password entry is rejected for some reason, keep trying. In general, most 6-8 letter passwords that contain at least one number work well. Of course, be sure it's easy for you to remember!

4.2. Installing applications

4.2.1. About Emacs applications

As an Emacs user, you can mentally divide applications into two categories: those that are native to Emacs (that is, those applications written specifically for Emacs), and those that are not (for example, command-line applications). If an application is not Emacs-native, you can still run it from the Emacs shell command line. To run the application, type the command M-x shell to start the shell then the appropriate command to start the application. If the application is native to Emacs, you can type M-x name-of-application to start the application. The application will run directly in the Emacs buffer.

Sometimes, even though an application wasn't designed specifically for Emacs, you can install a special wrapper file that makes Emacs think the application is Emacs-native. These special files have a .el, or Emacs-lisp, extension. After you've downloaded and installed a new application, if a .el file exists for it, you can download that file too. Place it in the correct directory, add the appropriate line to your .emacs file so that Emacs will recognize the application, and you'll be able to run the application as if it were native to Emacs.

As an Emacspeak user, you'll also want to know which applications are Emacspeak-enabled. These Emacspeak-enabled applications have a second special .el wrapper file that contains Emacspeak-specific commands that provide audio feedback just for that application. For a complete list of Emacspeak-enabled applications, see http://emacspeak.sourceforge.net/applications.html. All avaliable emacspeak-*.el files are included with Emacspeak, so you won't have to download them.

So, when you install a new application, you'll need the following three things:

  • The application.

  • A .el file for that application, if you want to run it directly from Emacs instead of from the Emacs shell command line.

  • An emacspeak-*.el file for the application, if you want to run it directly from Emacs and have it Emacspeak-enabled. Check in the /emacspeak/lisp directory to see if one exists for your application.

Whenever possible, this HOWTO tells you specifically whether or not an application is Emacs-native, and if not, where to get the special .el wrapper files if they are available.

4.2.2. Downloading your application

Once you've chosen a new application to install, you'll need to download it. Typically you'll use either FTP application or the wget application to download your new Linux application, since most of them are distributed only on the Internet. If you are unfamiliar with the FTP and wget applications, refer to Section 5.1, Downloading files, for information on how to use these applications to get your files.

Usually, the files you download will have some sort of extension (the letters after the "dot" or "period" in the file name) that denotes what type of file it is. If your file has a .gz or .tar extension, refer to Section 4.2.3 on uncompressing files. If your file has a .rpm extension, refer to Section 4.2.4 on installing RPMs.

4.2.3. Uncompressing files

Most files are compressed in at least one (and sometimes multiple) ways. You can tell how a file was compressed, and thus how to uncompress it, by the extensions on the file. The most common extensions are .tar and .gz, though there are others.

If your downloaded file has multiple extensions, you'll have to uncompress it one step at a time, uncompressing the last extension first. For example, if the file is named foo.tar.gz, complete the following steps:

  1. Start the Emacs shell using the command M-x shell.

  2. If necessary, use the cd (change directory) command to move to the directory that contains your downloaded file.

  3. At the Emacs shell command prompt, type gunzip foo.tar.gz. The file will be unzipped, leaving you with a file called foo.tar in your directory. Files with a .tar extension are commonly known as "tarballs."

  4. At the command prompt, type tar -xvf foo.tar. The tarball will be uncompressed, usually leaving either a single file or a new directory that contains a number of files.

    Some recent versions of the tar command will both uncompress and untar a file if you add the -z option. Thus, the command tar -xvfz foo.tar.gz would both uncompress and untar the file.

If you ended up with a new directory after you uncompressed your files, it probably contains files with names like INSTALL, NOTES, or README, among others. These files usually include instructions for installing that specific application. As each application may have a different installation process, you should read these files carefully and follow any instructions they may provide. You'll probably need to be the root user to actually install any applications, as only root usually has the necessary permissions.

If you ended up with a single file after uncompressing, it probably has either a .rpm extension or some other type of extension, such as .el. If it has a .rpm extension, refer to Section 4.2.4 on installing RPMs. If the file has some other extension, refer to the website where you downloaded it for more information.

4.2.4. Installing RPMs

If you downloaded or uncompressed a file that has a .rpm extension, you're in luck! It is a Red Hat Package Manager file that contains all the information it needs to install itself automatically. Assuming that your distribution supports RPMs, you can install the file as follows:

  1. Open a root shell using the command M-x emacspeak-root, which is bound to C-e C-r.

  2. At the command prompt, type rpm -xfv foo.rpm. A number of messages will scroll by, and you'll be returned to the command prompt once RPM finishes installing the files.

For additional information on RPMs, refer to Red Hat's official website, http://www.redhat.com or the official Red Hat Linux reference guide, at http://www.redhat.com/support/manuals/RHL-7-Manual/ref-guide/ch-rpm.html.