2 - Raspberry PI Community Projects

talk dgram udp wait nobody.tty /usr/sbin/in.talkd in.talkd
finger stream tcp nowait nobody /usr/sbin/tcpd /usr/sbin/in.fingerd
ident stream tcp nowait nobody /usr/sbin/identd identd -i
Example 9.1
Excerpt from /etc/inetd.conf
The tcpd program is frequently used in the /etc/inetd.conf file. It allows limiting incoming
connections by applying access control rules, documented in the hosts_access(5) manual page,
and which are configured in the /etc/hosts.allow and /etc/hosts.deny files. Once it has
been determined that the connection is authorized, tcpd executes the real server (like /usr/
bin/in.fingerd in our example).
COMMUNITY
Wietse Venema
Wietse Venema, whose expertise in security has made him a renowned programmer,
is the author of the tcpd program. He is also the main creator of
Postfix, the modular e-mail server (SMTP, Simple Mail Transfer Protocol), designed
to be safer and more reliable than sendmail, which features a long
history of security vulnerabilities.
ALTERNATIVE
Other inetd commands
There is no lack of alternatives. In addition to openbsd-inetd and netkit-inetd
already mentioned, there are inetutils-inetd, micro-inetd, rlinetd and xinetd.
This last incarnation of a super-server offers very interesting possibilities.
Most notably, its configuration can be split into several files (stored, of course,
in the /etc/xinetd.d/ directory), which can make an administrator's life easier.
9.7. Scheduling Tasks with cron and atd
cron is the daemon responsible for executing scheduled and recurring commands (every day,
every week, etc.); atd is that which deals with commands to be executed a single time, but at a
specific moment in the future.
In a Unix system, many tasks are scheduled for regular execution:
• rotating the logs;
• updating the database for the locate program;
• back-ups;
• maintenance scripts (such as cleaning out temporary files).
By default, all users can schedule the execution of tasks. Each user has thus their own crontab
in which they can record scheduled commands. It can be edited by running crontab -e (its
content is stored in the /var/spool/cron/crontabs/user file).
204 The Debian Administrator's Handbook