🚀5 最新Docker容器技术%26Docker-Compose实战教程 - 🐋[Docker] 硬盘空间去哪了？ - 《03 Container Runtime（CRI）》

在我的“系统学习Docker，践行DevOps理念”课程里，对于新手，我曾经说过，在玩docker的时候，尽量不要在自己电脑上(Mac或者windows)上直接安装docker和使用他，而是找一个虚拟机。Docker本身如果我们用的时间长了，会占用系统不少硬盘空间，特别是学习期间，今天拉一个image下来，明天又拉一个，今天建一个容器，明天建一个，久而久之，我们的电脑硬盘就吃紧了。如果是在虚拟机(vmware或者virtualbox),我们可以直接删除虚机，但是如果我们不想删除虚机，那如何清理docker所占的硬盘空间呢，本文我们一起来看看吧。首先，我们先准备一台docker host，比如下面，我们通过df命令先看看系统当前的硬盘空间。

[vagrant@localhost ~]$ docker version
Client:
 Version:      18.05.0-ce
 API version:  1.37
 Go version:   go1.9.5
 Git commit:   f150324
 Built:        Wed May  9 22:14:54 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm
Server:
 Engine:
  Version:      18.05.0-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.9.5
  Git commit:   f150324
  Built:        Wed May  9 22:18:36 2018
  OS/Arch:      linux/amd64
  Experimental: false
[vagrant@localhost ~]$ df -h
Filesystem                       Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup00-LogVol00   38G  1.3G   37G   4% /
devtmpfs                         236M     0  236M   0% /dev
tmpfs                            245M     0  245M   0% /dev/shm
tmpfs                            245M  4.5M  240M   2% /run
tmpfs                            245M     0  245M   0% /sys/fs/cgroup
/dev/sda2                       1014M   63M  952M   7% /boot
tmpfs                             49M     0   49M   0% /run/user/1000
tmpfs                             49M     0   49M   0% /run/user/0
[vagrant@localhost ~]$

系统现在用了1.3G空间，还有37G可用空间。首先我们先介绍一个命令，叫 docker system df ,我们看到目前我们没有任何镜像，容器，存储和cache。

[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              0                   0                   0B                  0B
Containers          0                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

我们拉一个image看看

[vagrant@localhost ~]$ docker pull alpine
Using default tag: latest
latest: Pulling from library/alpine
ff3a5c916c92: Pull complete
Digest: sha256:7df6db5aa61ae9480f52f0b3a06a140ab98d427f86d8d5de0bedab9b8df6b1c0
Status: Downloaded newer image for alpine:latest
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              1                   0                   4.148MB             4.148MB (100%)
Containers          0                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

创建一个容器，退出，我们看到其实这个容器本身并不占空间

[vagrant@localhost ~]$ docker run -d alpine
8b7f9b1e11b85c6d2335b17ea2c303cf500f2a19cccd57864fb1eeceb4021a5d
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              1                   1                   4.148MB             0B (0%)
Containers          1                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B

下面我们用Dockerfile基于alpine制作一个image，往这个image写入一个1G大小的文件，然后build完，我们看到系统空间多了1G，这个1G后面括号显示100%，这个100%意思是，这个空间可以100%回收，怎么回收？把这个docker image删了就回收了。

[vagrant@localhost ~]$ more Dockerfile
FROM alpine
RUN dd if=/dev/zero of=1g3.img bs=1G count=1
[vagrant@localhost ~]$ docker build -t test1 .
Sending build context to Docker daemon  125.4kB
Step 1/2 : FROM alpine
 ---> 3fd9065eaf02
Step 2/2 : RUN dd if=/dev/zero of=1g3.img bs=1G count=1
 ---> Running in 6d9e95f54e26
1+0 records in
1+0 records out
Removing intermediate container 6d9e95f54e26
 ---> 4ebfe90ead11
Successfully built 4ebfe90ead11
Successfully tagged test1:latest
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              2                   1                   1.078GB             1.078GB (100%)
Containers          1                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

我们再修改下dockerfile，改成写2个1G的文件，然后重新build，我们看到系统的空间变成了之前的两倍，并没有变成3G，也就是它用了之前的image作为cache

[vagrant@localhost ~]$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
test1               latest              4ebfe90ead11        3 minutes ago       1.08GB
alpine              latest              3fd9065eaf02        4 months ago        4.15MB
[vagrant@localhost ~]$ more Dockerfile
FROM alpine
RUN dd if=/dev/zero of=1g3.img bs=1G count=1
RUN dd if=/dev/zero of=1g3.img bs=1G count=1
[vagrant@localhost ~]$ docker build -t test1 .
Sending build context to Docker daemon  125.4kB
Step 1/3 : FROM alpine
 ---> 3fd9065eaf02
Step 2/3 : RUN dd if=/dev/zero of=1g3.img bs=1G count=1
 ---> Using cache
 ---> 4ebfe90ead11
Step 3/3 : RUN dd if=/dev/zero of=1g3.img bs=1G count=1
 ---> Running in 93929b2a75ce
1+0 records in
1+0 records out
Removing intermediate container 93929b2a75ce
 ---> 9fbb2427fc1d
Successfully built 9fbb2427fc1d
Successfully tagged test1:latest
[vagrant@localhost ~]$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
test1               latest              9fbb2427fc1d        5 seconds ago       2.15GB
alpine              latest              3fd9065eaf02        4 months ago        4.15MB
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              2                   1                   2.152GB             2.152GB (100%)
Containers          1                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

但是有时候我们并不会这么幸运，假如我们的Dockerfile变成

[vagrant@localhost ~]$ more Dockerfile
FROM alpine
RUN echo test
RUN dd if=/dev/zero of=1g3.img bs=1G count=1
RUN dd if=/dev/zero of=1g3.img bs=1G count=1

RUN echo test 的位置导致docker build image时候不会去使用之前的cache，那么灾难就来了。我们的image变成了3个，我们的系统空间占用变成了4G，之前的test1变成了一个, 这个僵尸image叫dangling images，这时候怎么办呢？

[vagrant@localhost ~]$ docker image ls
REPOSITORY          TAG                 IMAGE ID            CREATED             SIZE
test1               latest              8c32028a8557        45 seconds ago      2.15GB
<none>              <none>              9fbb2427fc1d        5 minutes ago       2.15GB
alpine              latest              3fd9065eaf02        4 months ago        4.15MB
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              3                   1                   4.299GB             4.299GB (100%)
Containers          1                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

这时候，其实我们手动通过docker image rm可以删除这两个容器，从而释放空间。但是有点麻烦对吧。这时候我们可以试试一个命令

<font style="color:rgb(28, 31, 33);background-color:rgb(248, 250, 252);">docker system prune</font>

[vagrant@localhost ~]$ docker system prune
WARNING! This will remove:
        - all stopped containers
        - all networks not used by at least one container
        - all dangling images
        - all build cache
Are you sure you want to continue? [y/N] y
Deleted Containers:
8b7f9b1e11b85c6d2335b17ea2c303cf500f2a19cccd57864fb1eeceb4021a5d
Deleted Images:
deleted: sha256:9fbb2427fc1dbaba37fd67a81f84970255e50325ea128aa06bcc60a138835ce8
deleted: sha256:63f58c3c4640f0ed9b1d917e2f01b0ca461929768712a4c8899cbf3b27f0d716
deleted: sha256:4ebfe90ead11af51f131372292709d590e4856bb6bf9855e1bd1e5b801920364
deleted: sha256:45f5bb8b1109d2e61b2aa4ab2d392582cbe89bba99d2e3a3d15192500ed5d22c
Total reclaimed space: 2.147GB
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              2                   0                   2.152GB             2.152GB (100%)
Containers          0                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

docker system prune会清理所有已停止的容器，没有被用的network，所有的僵尸image，还是build cache。能够迅速帮我们清理空间。当然docker system prune 我们可以加一个 -a 参数,这个就厉害了，除了删除之前docker system prune能删除的东西以外，他还会删除所有没有容器使用的image，比如

[vagrant@localhost ~]$ 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 Images:
untagged: alpine:latest
untagged: alpine@sha256:7df6db5aa61ae9480f52f0b3a06a140ab98d427f86d8d5de0bedab9b8df6b1c0
untagged: test1:latest
deleted: sha256:8c32028a8557a1bdd9cc0bdba9b0bb6e9f3c52e139c62de166b24ac3b2abddab
deleted: sha256:cf8eec9e8e0dfdb48a628e284a8bce27b5d6968e94baacc16ca47ef9d667dc82
deleted: sha256:91e956dd9cf9f736e9b0ee7a7211e91b6858ad746d3b1cf7713e1492da575c04
deleted: sha256:e7264a1948b8edae8f94172c5034d5223e4bf045d1d7eb00b431402d52528aec
deleted: sha256:8bbc26e497f57eb0caef4a26a06333f32522ab0d8fae32637a5a85c2d477436e
deleted: sha256:3fd9065eaf02feaf94d68376da52541925650b81698c53c6824d92ff63f98353
deleted: sha256:cd7100a72410606589a54b932cabd804a17f9ae5b42a1882bd56d263e02b6215
Total reclaimed space: 2.152GB
[vagrant@localhost ~]$ docker system df
TYPE                TOTAL               ACTIVE              SIZE                RECLAIMABLE
Images              0                   0                   0B                  0B
Containers          0                   0                   0B                  0B
Local Volumes       0                   0                   0B                  0B
Build Cache                                                 0B                  0B
[vagrant@localhost ~]$

test1这个好的image也被删了，因为没有容器使用它，所以 -a 参数要小心使用。