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 for short.
It's a good idea to use
apt to keep your software reasonably up to date.
apt update apt upgrade
Not only do up-to-date packages often come with more features, but they can also fix any possible security bugs.
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
-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.
For example, we can see that in
/var/log/nginx/, nginx produces both
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:
tail -n 25 /var/log/nginx/error.log
tail -n 25 means "show me the last 25 lines of this file."
You can replace that with
less to browse the whole file.
less, navigate with arrows or vim-keys and exit with
Another tool on systemd distributions is
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
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
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 nginx nginx: /usr/sbin/nginx /usr/lib/nginx /etc/nginx /usr/share/nginx /usr/share/man/man8/nginx.8.gz
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.
whereis can be used only with installed programs.
A more general tool is the pair of
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.
updatedb, try running
locate nginx to find all files with "nginx" in their name.
You can make your search more specific by chaining other Unix commands through pipes.
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.
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
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