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7. Troubleshooting

7.1 Booting Problems

Booting problems are generally rare, and generally only occur on old and buggy, or somehow non-compliant hardware. Booting problems can be associated with a number of problems, depending upon at what point during the boot process the failure occurs. The following are possible causes of failure when booting from a CD.

In general, hardware issues cause the majority of problems during the boot process of the Sentry Firewall CD, and may not always be easy to diagnose. Generally, the first step in debugging a general boot problem is to try and boot another CD in the same machine to attempt to rule out a hardware problem. And then attempt to boot the Sentry Firewall CD in another machine to attempt to rule out damage to the CD. If both these tests produce no negative results, then perhaps swap out the CDROM drives in the two machines, if possible, and do the test again. Then perhaps check out the general mailing list(mentioned below) for further assistance.

7.2 Configuration Problems

This section deals with configuration problems with the "sentry.conf" file. The sentry.conf configuration file, as mentioned in previous sections, tells the configuration scripts what to do during boot time to configure the running system. Syntax errors in the script can cause a file to be misplaced, or for the directive to not be parsed at all.

Error messages during the boot process of the Sentry Firewall CD can help greatly in diagnosing potential syntax or other types of errors. So watch the CD boot and write down any error messages that may pop up. Also, during bootup a logfile detailing the configuration process is created at /var/log/SENTRY_LOG. If you can log in to the system after it has booted, then take a look at this file for any obvious error messages.

7.3 Frequently Asked Questions

A FAQ is currently being maintained on the Sentry Firewall website, it can be accessed via the following URL:

7.4 Mailing List

Thanks to, there are mailing lists available for the Sentry CD. You can look through the archives, or subscribe to the general mailing list to ask questions or make comments. The following are links for the general Sentry-Users mailing list. Other mailing lists are listed at

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