Debian is the preferred choice of an operating system for all our IT Solutions for Small Business and Home users.
Debian is a free operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run. Debian provides more than a pure OS: it comes with over 59000 packages, precompiled software bundled up in a nice format for easy installation on your machine. Read more about Debian ...
Debian is under continual development. The latest release is Debian 10.3. It is also (currently) known as stable or by its codename "Buster". Each version also corresponds to a set of named software repositories (at least one per CPU architecture).
At any given time, there is one stable release of Debian, which has the support of the Debian security team. When a new stable version is released, the security team will usually cover the previous version for a year or so, while they also cover the new/current version. Only stable is recommended for production use.
There are also two main development repositories unstable and testing which are continually updated during the development of the next stable release. The latest packages arrive in unstable (which always has the codename "Sid"). Packages are automatically copied from unstable to testing when they meet criteria such as lack of release-critical bugs, and dependencies being satisfied by other packages in testing.
Debian Long Term Support (LTS) is a project to extend the lifetime of all Debian stable releases to (at least) 5 years. Debian LTS is not handled by the Debian security team, but by a separate group of volunteers and companies interested in making it a success.
Thus the Debian LTS team takes over security maintenance of the various releases once the Debian Security team stops its work. Read more about Debian Long Term Support here.
Extended Long Term Support (ELTS) is a commercial offering to further extend the lifetime of Debian releases (after the 5 years offered by the LTS project). It is not an official Debian project. Debian's infrastructure and other Debian resources are not involved. Read more about Debian Extended Long Term Support here.
Debian release timeline
|Version||Code Name||Release Date||EOL||EOL LTS||EOL ELTS|
Note: Only Debian versions with the current Standard, Long Term Support (LTS) or Extended Long Term Support (ELTS) are included in this timeline.
Servers are working around the clock doing their job as expected. But like any machine they do require some attention and maintenance to prevent server disastrous failures and data loss. An important part of the server maintenance is server monitoring performed by system administrators to ensure that the server is performing as expected and all problems are discovered and solved before they become serious.
Server monitoring can be done using either manual techniques or automated server monitoring software tools. Even if you are responsible for only 1 server, you will very soon realise that you need a monitoring tool. Yes, we humans need some healthy night sleep.
It is important for a system monitoring tool to just work - all the time, and you should be able to trust it to do so. A system monitoring tool needs to be non-intrusive and you should be able to forget about it once it's installed.
Our server monitoring tool of choice is the MONIT ( https://mmonit.com/monit/ ). Monit is a small Open Source utility for managing and monitoring Unix systems. Monit conducts automatic maintenance and repair and can execute meaningful causal actions in error situations.
That's what is exciting about Monit. Monit is more than just a passive monitoring tool. Suppose in the middle of the night apache is using too much resources (e.g. if a DoS attack is in progress) Monit can stop or restart apache and send you an alert message.
- Proactive: Monit can act if an error situation should occur, e.g. if Exim is not running, Monit can start it again and send you an alert.
- Monitoring daemon processes: Monit is particularly useful for monitoring daemon processes, such as those started at system boot time from /etc/init/ For instance postfix, sshd, apache, mysql, fail2ban, etc.
- Monitoring Files, Dirs and Filesystems: Monit can monitor these items for changes, such as timestamps changes, checksum changes or size changes. This is also useful for security reasons - you can monitor the md5 or sha1 checksum of files that should not change and get an alert or perform an action if they should change.
- Monitoring Network Connections: Network tests can be performed on a protocol level; Monit has built-in tests for the main Internet protocols, such as HTTP, SMTP etc. Even if a protocol is not supported you can still test the server as you can configure Monit to send any data and test the response from the server.
- Monitoring Programs and scripts: With Monit you can test programs or scripts at certain times, much like cron, but in addition, you can test the exit value of a program and perform an action or send an alert if the exit value indicates an error. This means that you can use Monit to perform any type of check you can write a script for.
- Monitoring General System Resources: Finally, Monit can be used to monitor general system resources on localhost such as overall CPU usage, Memory and Load Average.
- Built-in a lightweight HTTP(S) interface: You can use it to browse the Monit server and check the status of all monitored services. From the web-interface you can start, stop and restart processes and disable or enable monitoring of services.
Logging and Alerts
Monit can logging status and error messages to a file or via syslog. We are using dedicated Monit log file in our Debian based systems ( /var/log/monit.log ).
If an event occurs Monit will raise an alert. By default, Monit only sends alert notifications via email. Additionally, a script can be added to send alerts using other means. In our solutions we are using a customised Monit2Telegram script to send Monit alerts to Telegram messenger using a Telegram bot.