我发现这个方法最适合我:

docker image prune --all

默认情况下，Docker不会删除已命名的图像，即使它们未使用。该命令将删除未使用的映像。

注意，图像中的每一层都是/usr/lib/docker/overlay2/文件夹中的一个文件夹。

我使用了“docker system prune -a”，它清洗了卷和overlay2下的所有文件

    [root@jasontest volumes]# 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: ubuntu:12.04
    untagged: ubuntu@sha256:18305429afa14ea462f810146ba44d4363ae76e4c8dfc38288cf73aa07485005
    deleted: sha256:5b117edd0b767986092e9f721ba2364951b0a271f53f1f41aff9dd1861c2d4fe
    deleted: sha256:8c7f3d7534c80107e3a4155989c3be30b431624c61973d142822b12b0001ece8
    deleted: sha256:969d5a4e73ab4e4b89222136eeef2b09e711653b38266ef99d4e7a1f6ea984f4
    deleted: sha256:871522beabc173098da87018264cf3e63481628c5080bd728b90f268793d9840
    deleted: sha256:f13e8e542cae571644e2f4af25668fadfe094c0854176a725ebf4fdec7dae981
    deleted: sha256:58bcc73dcf4050a4955916a0dcb7e5f9c331bf547d31e22052f1b5fa16cf63f8
    untagged: osixia/openldap:1.2.1
    untagged: osixia/openldap@sha256:6ceb347feb37d421fcabd80f73e3dc6578022d59220cab717172ea69c38582ec
    deleted: sha256:a562f6fd60c7ef2adbea30d6271af8058c859804b2f36c270055344739c06d64
    deleted: sha256:90efa8a88d923fb1723bea8f1082d4741b588f7fbcf3359f38e8583efa53827d
    deleted: sha256:8d77930b93c88d2cdfdab0880f3f0b6b8be191c23b04c61fa1a6960cbeef3fe6
    deleted: sha256:dd9f76264bf3efd36f11c6231a0e1801c80d6b4ca698cd6fa2ff66dbd44c3683
    deleted: sha256:00efc4fb5e8a8e3ce0cb0047e4c697646c88b68388221a6bd7aa697529267554
    deleted: sha256:e64e6259fd63679a3b9ac25728f250c3afe49dbe457a1a80550b7f1ccf68458a
    deleted: sha256:da7d34d626d2758a01afe816a9434e85dffbafbd96eb04b62ec69029dae9665d
    deleted: sha256:b132dace06fa7e22346de5ca1ae0c2bf9acfb49fe9dbec4290a127b80380fe5a
    deleted: sha256:d626a8ad97a1f9c1f2c4db3814751ada64f60aed927764a3f994fcd88363b659
    untagged: centos:centos7
    untagged: centos@sha256:2671f7a3eea36ce43609e9fe7435ade83094291055f1c96d9d1d1d7c0b986a5d
    deleted: sha256:ff426288ea903fcf8d91aca97460c613348f7a27195606b45f19ae91776ca23d
    deleted: sha256:e15afa4858b655f8a5da4c4a41e05b908229f6fab8543434db79207478511ff7

    Total reclaimed space: 533.3MB
    [root@jasontest volumes]# ls -alth
    total 32K
    -rw-------  1 root root  32K May 23 21:14 metadata.db
    drwx------  2 root root 4.0K May 23 21:14 .
    drwx--x--x 14 root root 4.0K May 21 20:26 ..

背景

The blame for the issue can be split between our misconfiguration of container volumes, and a problem with docker leaking (failing to release) temporary data written to these volumes. We should be mapping (either to host folders or other persistent storage claims) all of out container's temporary / logs / scratch folders where our apps write frequently and/or heavily. Docker does not take responsibility for the cleanup of all automatically created so-called EmptyDirs located by default in /var/lib/docker/overlay2/*/diff/*. Contents of these "non-persistent" folders should be purged automatically by docker after container is stopped, but apparently are not (they may be even impossible to purge from the host side if the container is still running - and it can be running for months at a time).

解决方案

解决方案需要仔细的手动清理，虽然已经在其他地方描述过，但您仍然可以从我的案例研究中找到一些提示，我试图使其尽可能具有启发性和普遍性。

所以发生的事情是罪魁祸首应用程序(在我的案例中是claire -scanner)设法在几个月内向docker的overlay2的/diff/tmp子文件夹写入了数百gb的数据

du -sch /var/lib/docker/overlay2/<long random folder name seen as bloated in df -haT>/diff/tmp

271G total

因此，由于/diff/tmp中的所有子文件夹都是相当自解释的(都是克莱尔-scanner-*的形式，并且有过时的创建日期)，我停止了相关的容器(docker stop clair)，并小心地从diff/tmp中删除了这些过时的子文件夹，谨慎地从一个(最古老的)单一文件夹开始，并测试了对docker引擎的影响(这需要重新启动[systemctl restart docker]来回收磁盘空间):

rm -rf $(ls -at /var/lib/docker/overlay2/<long random folder name seen as bloated in df -haT>/diff/tmp | grep clair-scanner | tail -1)

我回收了数百gb的磁盘空间，而不需要重新安装docker或清除它的整个文件夹。所有正在运行的容器都必须在某一时刻停止，因为需要重新启动docker守护进程来回收磁盘空间，因此首先要确保您的故障转移容器在某个/其他节点上正确运行。我希望docker的prune命令也能覆盖过时的/diff/tmp(甚至/diff/*)数据(通过另一个开关)。

这是一个有3年历史的问题，你可以在Docker论坛上阅读它丰富多彩的历史，其中针对上述解决方案的应用程序日志的变体在2019年被提出，并且似乎在几个设置中起了作用:https://forums.docker.com/t/some-way-to-clean-up-identify-contents-of-var-lib-docker-overlay/30604

在上面的评论中，人们建议修剪系统，如清除悬空卷，图像，退出容器等，有时你的应用程序成为罪魁祸首，它在很短的时间内产生了太多的日志，如果你使用一个空的目录卷(本地卷)，这会填满/var分区。在这种情况下，我发现下面的命令非常有趣，要弄清楚是什么在消耗我的/var分区磁盘上的空间。

du -ahx /var/lib | sort -rh | head -n 30

This command will list top 30, which is consuming most space on a single disk. Means if you are using external storage with your containers, it consumes a lot of time to run du command. This command will not count mount volumes. And is much faster. You will get the exact directories/files which are consuming space. Then you can go to those directories and check which files are useful or not. if these files are required then you can move them to some persistent storage by making change in app to use persistent storage for that location or change location of that files. And for rest you can clear them.

警告:不要在生产系统中使用

/# df
...
/dev/xvda1      51467016 39384516   9886300  80% /
...

好的，让我们先尝试系统修剪

#/ docker system prune --volumes
...
/# df
...
/dev/xvda1      51467016 38613596  10657220  79% /
...

不太好，好像清理了几兆。让我们疯狂起来吧:

/# sudo su
/# service docker stop
/# cd /var/lib/docker
/var/lib/docker# rm -rf *
/# service docker start
/var/lib/docker# df
...
/dev/xvda1      51467016 8086924  41183892  17% /
...

好了! 只需要记住，除了一次性服务器，不建议使用这种方法。此时，Docker的内部数据库将无法找到任何这些覆盖，这可能会导致意想不到的后果。

我最近遇到了一个类似的问题，overlay2变得越来越大，但我不知道是什么消耗了大量的空间。

df告诉我overlay2的大小大约是24GB。

对于du，我试图找出是什么占据了空间，但失败了。

区别来自于删除的文件(在我的情况下主要是日志文件)仍然被一个进程(Docker)使用。因此，文件不会显示du，但它占用的空间将显示df。

重新启动主机有帮助。重新启动docker容器可能已经有所帮助了…… org上的这篇文章帮助我找到了答案。