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如何彻底清除 Docker 占用的存储空间呢
How do I clean up the disk space occupied by Docker?
As a faith-based technology company, our fundebug background uses a cool, fully docker architecture, with all services, including databases, running in Docker. This is certainly not for the sake of dazzle skill, the benefit that sees clearly is still a lot of:
- The configuration of all servers is very simple, only Docker installed, so the new server is much simpler.
- It’s easy to move a variety of services between servers, download the Docker mirror and run without having to manually configure the running environment.
- The development/testing environment is in strict conformity with the production environment, without fear of a deployment failure due to environmental problems.
At least, on the line for more than a year, Docker has been very stable, there is no problem. However, it has a modest problem that consumes more disk space.
If Docker accidentally fills up the disk space and your service is over, all Docker users need to be vigilant . Of course, we should not be nervous, this problem is very good solution.
1. Docker system command
In who ran out of disk? In the Docker system command detailed, we detail the Docker System command, which can be used to manage disk space.
Docker System DF command, similar to the DF command on Linux, to view disk usage for Docker:
docker system df
TYPE TOTAL ACTIVE SIZE RECLAIMABLE
Images 147 36 7.204GB 3.887GB (53%)
Containers 37 10 104.8MB 102.6MB (97%)
Local Volumes 3 3 1.421GB 0B (0%)
Build Cache 0B 0B
The Docker Mirror uses the 7.2GB disk, the Docker container occupies the 104.8MB disk, and the Docker data volume occupies the 1.4GB disk.
The Docker system Prune command can be used to clean up disks, remove closed containers, useless data volumes and networks, and dangling mirrors (that is, mirrors without tag). The Docker system prune-a command cleans more thoroughly, eliminating the use of Docker mirrors with no containers. Note that these two commands delete the container you have temporarily closed, and the Docker mirror image that you have temporarily not used … So you must think clearly before using.
After the Docker system prune-a command is executed, Docker consumes a lot less disk space:
docker system df
TYPE TOTAL ACTIVE SIZE RECLAIMABLE
Images 10 10 2.271GB 630.7MB (27%)
Containers 10 10 2.211MB 0B (0%)
Local Volumes 3 3 1.421GB 0B (0%)
Build Cache 0B 0B
2. Manually clean docker mirrors/containers/data volumes
For older versions of Docker (prior to version 1.13), there is no Docker system command, so manual cleanup is required. Here are some common life Remove all closed containers
docker ps -a | grep Exit | cut -d ' ' -f 1 | xargs docker rm
Delete all dangling mirrors (that is, mirror without tag):
docker rmi $(docker images | grep "^<none>" | awk "{print $3}")
Delete all dangling data volumes (that is, useless volume):
docker volume rm $(docker volume ls -qf dangling=true)
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3. Limit container Log Small
Once, when I cleaned up the disk using the methods mentioned in 1 and 2, I did a series of analyses.
On Ubuntu, all related files for Docker, including mirrors, containers, and so on, are stored in the /var/lib/docker/directory:
du -hs /var/lib/docker/
97G /var/lib/docker/
It’s enough that Docker used nearly 100GB disks. To continue with the du command, you can navigate to a directory that really consumes so many disks:
92G /var/lib/docker/containers/a376aa694b22ee497f6fc9f7d15d943de91c853284f8f105ff5ad6c7ddae7a53
It is known by Docker PS that the ID of the Nginx container is exactly a376aa694b22, with the above directory /var/lib/docker/containers/a376aa694b22 the prefix for the is consistent:
docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a376aa694b22 192.168.59.224:5000/nginx:1.12.1 "nginx -g 'daemon off" 9 weeks ago Up 10 minutes nginx
As a result, the Nginx container occupies a disk of 92GB . Further analysis shows that the real disk space consumption is nginx log files. Then it is not difficult to understand. Our fundebug daily data requests are millions, so the log data is naturally very large.
You can use the truncate command to “clear 0” of the Nginx container’s log file:
truncate -s 0 /var/lib/docker/containers/a376aa694b22ee497f6fc9f7d15d943de91c853284f8f105ff5ad6c7ddae7a53/*-json.log
Of course, this command is only temporary effect, the log file will rise back sooner or later. To solve the problem fundamentally, you need to limit the log file size of the Nginx container . This can be done by configuring the log’s max-size , which is the Docker-compose configuration file for the Nginx container:
nginx:
image: nginx:1.12.1
restart: always
logging:
driver: "json-file"
options:
max-size: "5g"
After restarting the Nginx container, the size of its log file is limited to 5GB, so don’t worry anymore ~
4. Restart Docker
Also once , when I cleaned out mirrors, containers, and data volumes, I found that there was no reduction in disk space. Based on the recommendations mentioned in Docker disk usage , I restarted Docker and found that disk usage dropped from 83% to 19%. Depending on the master pointing , this should be a bug related to kernel 3.13, causing Docker to be unable to clean up some unwanted directories:
It’s quite likely that for some reason when those container shutdown, Docker couldn ‘ t remove the directory because the SHM Device was busy. This tends to happen often on 3.13 kernel. You may want to update it to the 4.4 version supported on trusty 14.04.5 LTS.
The reason it disappeared after a restart, is that daemon probably tried and succeeded to clean up left over data from Sto pped containers.
I looked at the kernel version and found it was 3.13:
uname -r
3.13.0-86-generic
If your kernel version is also 3.13, and the disk is not successful, you may wish to reboot the Docker. Of course, this evening operation is more reliable.
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