Creating Problems

Even experienced system administrators make mistakes; new system administrators just make more mistakes. Although you can improve your odds of avoiding problems by carefully reading and following the documentation provided with software, many things can still go wrong. A comprehensive list is not possible, no matter how long, as new and exciting ways to create problems are discovered every day. A few of the more common techniques are described here.

Failing to Perform Regular Backups

Few feelings are more painful to a system administrator than realizing that important information is lost forever. If your system supports multiple users, having a recent backup may be your only protection from a public lynching. If it is a single-user system, having a recent backup certainly keeps you happier when you lose a hard disk.

Not Reading and Following Instructions

Software developers provide documentation for a reason. Even when you have installed a software package before, carefully read the instructions again. They may have changed, or you may simply remember them incorrectly. Software changes more quickly than books are revised, so no book should be taken as offering foolproof advice. Instead, look for the latest documentation online.

Failing to Ask for Help When Instructions Are Not Clear

If something does not seem to make sense, try to find out what does make sensedo not guess. Refer to "Help" on page 977.

Deleting or Mistyping a Critical File

One sure way to give yourself nightmares is to execute the command

# # rm rf /etc        Perhaps no other command renders a Linux system useless so quickly. The only recourse is to reboot into rescue mode (page 397) using the first installation CD and restore the missing files from a recent backup. Although this example depicts an extreme case, many files are critical to proper operation of a system. Deleting one of these files or mistyping information in one of them is almost certain to cause problems. If you directly edit /etc/passwd, for example, entering the wrong information in a field can make it impossible for one or more users to log in. Do not use rm rf with an argument that includes wildcard characters; do pause after typing the command, and read it before you press RETURN. Check everything you do carefully, and make a copy of a critical file before you edit it.

Caution: Be careful when using a wildcard character with rm

When you must use a wildcard character, such as *, in an argument to an rm command, first use echo with the same argument to see exactly which files you will be deleting. This check is especially important when you are working as root.