2 - Raspberry PI Community Projects

DEBIAN POLICY
Preserving changes
The Debian Policy expressly stipulates that everything should be done to preserve
manual changes made to a configuration file, so more and more scripts
take precautions when editing configuration files. The general principle is
simple: the script will only make changes if it knows the status of the configuration
file, which is verified by comparing the checksum of the file against
that of the last automatically generated file. If they are the same, the script
is authorized to change the configuration file. Otherwise, it determines that
the file has been changed and asks what action it should take (install the new
file, save the old file, or try to integrate the new changes with the existing
file). This precautionary principle has long been unique to Debian, but other
distributions have gradually begun to embrace it.
The ucf program (from the Debian package of the same name) can be used to
implement such a behavior.
9.5. syslog System Events
9.5.1. Principle and Mechanism
The rsyslogd daemon is responsible for collecting service messages coming from applications
and the kernel, then distributing them into log files (usually stored in the /var/log/ directory).
It obeys the /etc/rsyslog.conf configuration file.
SUPPLEMENTS
Moving from sysklogd to
rsyslog
Debian Squeeze installs rsyslog by default, while older versions (up to Etch, but
not Lenny) used sysklogd. The transition was not automatic, and in the case
of an upgrade from Etch, rsyslog should be installed manually if you want to
keep in sync with Debian's default choice.
Migration from one to the other is painless, since the default configuration is
very similar, and the syntax of the older /etc/syslog.conf is compatible with
the new /etc/rsyslog.conf.
Each log message is associated with an application subsystem (called “facility” in the documentation):
• auth and authpriv: for authentication;
• cron: comes from task scheduling services, cron and atd;
• daemon: affects a daemon without any special classification (DNS, NTP, etc.);
• p: concerns the FTP server;
• kern: message coming from the kernel;
• lpr: comes from the printing subsystem;
• mail: comes from the e-mail subsystem;
200 The Debian Administrator's Handbook