Maintaining a Server – LandChad.net

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Here are some important topics you should be familiar with whenever you are managing a server.

Keep packages up to date.

All GNU/Linux distributions use package managers to easily be able to install and update packages without manually downloading them. + On Debian, which we use here for these tutorial the package manager is apt-get or apt for short. +

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+ It's a good idea to use apt to keep your software reasonably up to date. +

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apt update
+apt upgrade

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+ Not only do up-to-date packages often come with more features, but they can also fix any possible security bugs. +

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Troubleshooting general problems

+ Often when you are installing something new, you might miss a step and run into an error, so it's important to know how to check and see what errors have happened on your computer. +

On Debian and other GNU/Linux distributions that use systemd (most of them), you can use the command journalctl to look at the system's general log. + You will probably want to run journalctl -xe as the -x and -e as that gives the most information and starts you at the bottom of the log to see the most recent errors. +

+ Some programs do not use this system log, but have their own logs stored in /var/log/, or sometimes it's more convenient to look at a specific program's log to see only its issues. +

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For example, we can see that in /var/log/nginx/, nginx produces both error and access files. + The access files show you all the times people connect to files on your server and much more. + We can look at the most recent errors by running: +

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tail -n 25 /var/log/nginx/error.log

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+ The command tail -n 25 means "show me the last 25 lines of this file." + You can replace that with less to browse the whole file. + In less, navigate with arrows or vim-keys and exit with q. +

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systemctl

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+ Another tool on systemd distributions is systemctl. + At a basic level, use systemctl status put-service-name-here + to see if a system service is running and its most recent log. + But there's much more to systemctl. +

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+ For example, you can run systemctl stop nginx to stop NginX and systemctl start nginx to start it back up (or use restart for both). + When you make changes to a program's configuration files, reload well make them reload them. + If you no longer want a service to start when the system is rebooted, use disable, or conversely, to make a service start on reboot use enable. +

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Cronjobs

+ You might want to have your server automatically run commands (like updating something) at a set time without having to tell it. + We can create a "cronjob" to schedule one of these regular commands. + To create a cronjob, simply run: +

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crontab -e

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+ In this crontab file, we can add a line for a command. + Here is an example: +

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unfinished

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Finding Files

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+ Especially if you're new to how a GNU/Linux system is arranged, you might need help finding files. + To find program-related files, you can just use whereis: +

$ whereis nginx
+nginx: /usr/sbin/nginx /usr/lib/nginx /etc/nginx /usr/share/nginx /usr/share/man/man8/nginx.8.gz

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This command lists the directories related to that program. For example, /etc/nginx is where the configuration files are and /usr/share/nginx is where the library and module-like files are.

But whereis can be used only with installed programs. + A more general tool is the pair of updatedb and locate. +

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+ updatedb is a command that quickly indexes every file and directory on your computer. + Then you can run locate to find a file containing a given name. + After running updatedb, try running locate nginx to find all files with "nginx" in their name. +

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+ You can make your search more specific by chaining other Unix commands through pipes. + For example, grep takes input and returns only lines that match an extra argument. + In the example below, we locate all files with "nginx" in the name, but we use grep to only show us those with the word "available" in them. +

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root@landchad:~# locate nginx | grep available
+/etc/nginx/modules-available
+/etc/nginx/sites-available
+/etc/nginx/sites-available/default
+/etc/nginx/sites-available/landchad
+/usr/share/nginx/modules-available
+/usr/share/nginx/modules-available/mod-http-auth-pam.conf
+/usr/share/nginx/modules-available/mod-http-dav-ext.conf
+/usr/share/nginx/modules-available/mod-http-echo.conf
+/usr/share/nginx/modules-available/mod-http-geoip.conf
+/usr/share/nginx/modules-available/mod-http-image-filter.conf
+/usr/share/nginx/modules-available/mod-http-subs-filter.conf
+/usr/share/nginx/modules-available/mod-http-upstream-fair.conf
+/usr/share/nginx/modules-available/mod-http-xslt-filter.conf
+/usr/share/nginx/modules-available/mod-mail.conf
+/usr/share/nginx/modules-available/mod-stream.conf

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+ updatedb is an ideal candidate for a cronjob so you don't have to worry about running each time. + For example, adding the following to your crontab will run updatedb every 30 minutes: +

*/30 * * * * /usr/bin/updatedb