Introduction.

2 Introduction.

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Noun:

One who administers; one who manages, carries on, or directs the affairs of any establishment or institution.
One who has the faculty of managing or organizing.
One who executes or performs the official duties of religion, justice, etc.; one who dispenses or ministers to the public in such matters.
One to whom authority is given to manage estates, etc. for the legal owner during his minority, incapacity, etc.; a trustee, a steward. esp. in Sc. Law. `A person legally empowered to act for another whom the law presumes incapable of acting for himself' (Encyc.Brit.), as the father of children under age.
The bottom line: Administration of a Unix system on the Internet -- or any other system, for that matter -- is a full-time responsibility, not a part-time, casual activity.

Performing backups
Adding and removing users
Adding and removing hardware
Restoring files from backups that users have accidentally deleted
Installing new software
Answering users' questions
Monitoring system activity, disc use and log files
Figuring out why a program has stopped working since yesterday, even though the user didn't change anything; honest!
Monitoring system security
Adding new systems to the network
Talking with vendors to determine if a problem is yours or theirs, and getting them to fix it when it is their problem
Figuring out why "the network" (or "Pine", or "the computer") is so slow
Trying to free up disc space
Rebooting the system after a crash (usually happens when you are at home or have to catch a bus)
Writing scripts to automate as many of the above tasks as possible

$HOME is / (Watch what you delete!)
Change the password frequently and use "good" passwords (more on this later)
Remove the current working directory (a.k.a., ".") from your PATH
Never leave the terminal unattended, even for "just a minute"
Limit who has the root password to as few people as possible
Never execute any regular user's program as root (possible Trojan Horse)
Never let anyone else run a command as root, even if you are watching them
You risk having your password stolen by "sniffers" if you use programs like "telnet", "ftp", access email remotely with POP/IMAP (anything protocol involving "clear-text" passwords)