Apple Xserve Up Mac OS X Server Specifications download pdf (Page 27)

Chapter 1 Executing Commands 27

The sudo command gives root user privileges to users specified in the sudoers file.

If you’re logged in as an administrator user and your username is specified in the

etc/sudoers file, you can use this command.

To execute a single command with root user privileges, begin the command with sudo

(short for super user do). For example:

$ sudo serveradmin list

If you haven’t used sudo recently, you’re prompted for your administrator password.

To switch to the root user so you don’t need to repeatedly enter sudo, use the su

command:

$ su root

or simply:

$ su

You’re prompted for the root user password and are then logged in as the root user

until you log out or use the su command to switch to another user.

Note: The root user password is set to the administrator user password when you

install Mac OS X Server.

Important: To avoid running commands as root, log out after you finish using the su

command.

For more information about the sudo and su commands, see their man pages.

Terminating Commands

To terminate the currently running command, enter Control-C. This keyboard shortcut

sends an abort signal to the command. In most cases this causes the command to

terminate, although commands can install signal handlers to trap this signal and

respond differently.

Scheduling Tasks

To schedule tasks to run at defined times, use the cron tool. This tool is a daemon that

executes scheduled commands defined in crontab files.

The

cron tool searches the /var/cron/tabs/ folder for crontab files that are named after

accounts in /etc/passwd, and loads the files into memory. The

cron tool also searches

for crontab files in the /etc/crontab/ folder, which are in a different format. cron then

cycles every minute, examining stored crontab files and checking each command to

see if it should be run in the current minute.

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Apple Xserve Up Mac OS X Server Specifications Page 27