2 - Raspberry PI Community Projects

GOING FURTHER
GPS modules and other time
sources
If time synchronization is particularly crucial to your network, it is possible to
equip a server with a GPS module (which will use the time from GPS satellites)
or a DCF-77 module (which will sync time with the atomic clock near
Frankfurt, Germany). In this case, the configuration of the NTP server is a
lile more complicated, and prior consultation of the documentation is an
absolute necessity.
8.9.3. Rotating Log Files
Log files can grow, fast, and it is necessary to archive them. The most common scheme is a
rotating archive: the log file is regularly archived, and only the latest X archives are retained.
logrotate, the program responsible for these rotations, follows directives given in the /etc/
logrotate.conf file and all of the files in the /etc/logrotate.d/ directory. The administrator
may modify these files, if they wish to adapt the log rotation policy defined by Debian. The
logrotate(1) man page describes all of the options available in these configuration files. You
may want to increase the number of files retained in log rotation, or move the log files to a
specific directory dedicated to archiving them rather than delete them. You could also send
them by e-mail to archive them elsewhere.
The logrotate program is executed daily by the cron scheduling program (described in Section
9.7, “Scheduling Tasks with cron and atd” (page 204)).
8.9.4. Sharing Administrator Rights
Frequently, several administrators work on the same network. Sharing the the root passwords
is not very elegant, and opens the door for abuse due to the anonymity such sharing creates.
The solution to this problem is the sudo program, which allows certain users to execute certain
commands with special rights. In the most common use case, sudo allows a trusted user to execute
any command as root. To do so, the user simply executes sudo command and authenticates
using their personal password.
When installed, the sudo package doesn't give anyone any rights. To delegate such rights, the
administrator must use the visudo command, which allows them to modify the /etc/sudoers
configuration file (here again, this will invoke the vi editor, or any other editor indicated in the
EDITOR environment variable). Adding a line with username ALL=(ALL) ALL allows the user in
question to execute any command as root.
More sophisticated configurations allow authorization of only specific commands to specific
users. All the details of the various possibilities are given in the sudoers(5) man page.
170 The Debian Administrator's Handbook