[docker] Clean up docker system junk files, save disk space, keep the latest image, use the docker system command

1. The disk is full after docker runs for a while

Since releases and builds are often required, server machines are chosen from less disk space.
50G

Especially when building the front end and building golang, the image file must be downloaded every time. There will be a lot of build cache.

On the contrary, the real useful mirror image does not take up much space.

# df -lh
文件系统        容量  已用  可用 已用% 挂载点
devtmpfs        3.8G     0  3.8G    0% /dev
tmpfs           3.8G   24K  3.8G    1% /dev/shm
tmpfs           3.8G  908K  3.8G    1% /run
tmpfs           3.8G     0  3.8G    0% /sys/fs/cgroup
/dev/vda1        50G   49G     0  100% /
tmpfs           773M     0  773M    0% /run/user/0
overlay          50G   49G     0  100% /data/docker/overlay2/ff113c990677624e519763d002699fae39bcf58c0e005a7100253435718eb2a0/merged
overlay          50G   49G     0  100% /data/docker/overlay2/cefe857f8a1a40cd3d4fc9f95352fe71aa4a3e85210412e89612d97ad54f7b4d/merged
overlay          50G   49G     0  100% /data/docker/overlay2/f39ac164064163d69e8474b070d870a22ccb4dcf4f8b907d9b5ed58675de8348/merged
overlay          50G   49G     0  100% /data/docker/overlay2/18237ec943d64472a4d42789b70892cdc0727d7cf65cefc4aede49068241a4dc/merged

2, docker official cleaning

First check the disk usage using the command:

# docker system df
TYPE            TOTAL     ACTIVE    SIZE      RECLAIMABLE
Images          4         4         764.4MB   0B (0%)
Containers      4         3         2B        0B (0%)
Local Volumes   0         0         0B        0B
Build Cache     274       0         32.84GB   32.84GB

Then use the cleanup command:

#  docker system prune -a
WARNING! This will remove:
  - all stopped containers
  - all networks not used by at least one container
  - all images without at least one container associated to them
  - all build cache

Are you sure you want to continue? [y/N] y
Deleted Containers:
1ff34a648fa8b47476dc76080874d5c6c1d73fd5bbac79fff4cb0e3f639673bd

Deleted Images:
untagged: redis:bullseye
untagged: 
deleted: sha256:eca1379fe8b541831fd5ce4a252c263db0cef4efbfd428a94225dc020aaeb1af
deleted: sha256:21acda8c08f1a6109e2fb61ed010d368ee6581cf30128cdaab0e6b91dabffc22
...

Deleted build cache objects:
jcgsxqae4dviszzlx6g2ygfou
1chpzs27wr8a5x41hoshzd8pd
...
7c7wsj7e2rcu3o49xbgnoqid9
4f16uvjz4h7bsklayvfcftsf3

Total reclaimed space: 32.95GB

Cleaned up space:

# df -lh
文件系统        容量  已用  可用 已用% 挂载点
devtmpfs        3.8G     0  3.8G    0% /dev
tmpfs           3.8G   24K  3.8G    1% /dev/shm
tmpfs           3.8G  828K  3.8G    1% /run
tmpfs           3.8G     0  3.8G    0% /sys/fs/cgroup
/dev/vda1        50G  6.4G   41G   14% /
tmpfs           773M     0  773M    0% /run/user/0
overlay          50G  6.4G   41G   14% /data/docker/overlay2/18237ec943d64472a4d42789b70892cdc0727d7cf65cefc4aede49068241a4dc/merged
overlay          50G  6.4G   41G   14% /data/docker/overlay2/f39ac164064163d69e8474b070d870a22ccb4dcf4f8b907d9b5ed58675de8348/merged
overlay          50G  6.4G   41G   14% /data/docker/overlay2/ff113c990677624e519763d002699fae39bcf58c0e005a7100253435718eb2a0/merged

3. Reduced to 14%

Save a lot of space. The mirror used at the same time is still there.
Very convenient. You can continue to use docker.