Docker eats /var space how I can save some?

Question

Because there are some good comments on this question I thought that they could be good answers and beneficial, in this particular question.

Therefore in order to be able to be more beneficial for the community, I thought to be able to get answered here.

In my gnu/linux system I have the /var as big as 20G but due to use with docker and the development of custom docker images the /var takes the 90% of the space so how can I same some space in /var?

I originally thought to do some backup as this question says, then repartition the /var. But seems too laborious to me. Is there a safer and less time-consuming alternative?

Clear dangling images and such? Have tried checking which images are taking the most space? — muru, Jun 29 '19 at 15:27
Well this is a solution that you can make a full answer of it. — Dimitrios Desyllas, Jun 29 '19 at 15:29

score 4 · Accepted Answer · answered Jun 29 '19 at 18:21

If you have not done so for a while, then run docker system prune. It will run the garbage collector, and free a lot of disk space.

Note it may cause more work to be done next time you do something (such as build, pull, …), but should not remove anything that can not be got back.

score 1 · Answer 2 · edited Dec 19 '22 at 09:19

An alternative approach is to rsync the folder /var/lib/docker into a larger disk/partition. In my case, the partitions that contain /home/ has some heaps of free space; therefore I followed these steps:

I made a dedicated folder in /home/ named docker
```
mkdir /home/docker
```
Using rsync, I copied the data to /home/docker
```
rsync -av /var/lib/docker/ /home/docker
```
This makes /home/docker an exact copy of /var/lib/docker. Note that the trailing slash on the source directory is deliberate. Without it, you would get a docker directory inside /home/docker.
I checked how the rsync process went:
```
ls -l /home/docker
```
I terminated the docker daemon: (I'm using Ubuntu; therefore, using service was working fine, also using systemctl will do the job in most distros)
```
sudo service docker stop
```
Remove the /var/lib/docker
```
rm -rf /var/lib/docker
```

Symlink into /home/docker

sudo ln -s /home/docker /var/lib/docker

Start docker once again:
```
sudo service docker start
```

Docker eats /var space how I can save some?

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