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How to manually clean up your server's disk space

There are several ways to clean up your server’s disk space.

To check how much disk space you have, run the following command:

df -h

This will output a table like this:

Filesystem      Size  Used Avail Use% Mounted on
devtmpfs         97M     0   97M   0% /dev
tmpfs           969M   52K  969M   1% /dev/shm
tmpfs           485M  3.8M  481M   1% /run
tmpfs           969M  432K  968M   1% /run/wrappers
/dev/sda1        19G  8.2G  9.5G  47% /
/dev/sdb         18G   62M   17G   1% /volumes/sdb
tmpfs           194M     0  194M   0% /run/user/0

Here, the filesystem mounted on just / is your system volume.

Deleting old NixOS generations

NixOS allows you to roll back to previous system states at any time, at the cost of disk space. SelfPrivacy servers are configured to reclaim disk space by automatically deleting old system states, but only states older than 7 days are deleted, so you can still use the rollback feature.

It is possible to manually delete all old system states, and it may give you more much needed disk space. To do this, simply run the following command as root:

nix-collect-garbage -d

This operation might take a while, depending on the number of system states you have. When it is done, you will see how much disk space you have freed up.

Deleting old logs

Logs sometimes may take up quite a lot of disk space. On SelfPrivacy servers, system logs are always limited to 500MiB, but these are not the only log files you have on your server.

To check how much disk space logs take up, run the following command:

du -h --max-depth=1 /var/log

The output will look something like this:

4.0K	/var/log/private
14M     /var/log/nginx
499M	/var/log/journal
587M	/var/log

System journal

Here, /var/log/journal are the system logs where all apps usually write their logs. As you can see in this example, they respect the 500MiB limit.

If you want to clear all system logs, run the following command:

journalctl --rotate && journalctl --vacuum-time=1s

This will usually give you around 450 MiB of free disk space, but not for long. This may though be enough to run some commands that will free up more space.

Nginx logs

The /var/log/nginx directory contains logs for the Nginx web server. If they got too big, you can clear them by running:

rm /var/log/nginx/* && systemctl reload nginx

As you can see, we don’t just delete the files, but also reload Nginx. This is because Nginx will get confused by the missing log files, and they will not be recreated until Nginx is reloaded.