First of all -- it stores the virtual disk under ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2.
In the next step I have copied this file into the folder where a Vagrant Linux VM run, listed content, found a running Docker container and shrunk virtual disk:
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| # Show some info about the virtual disk | |
| mymac> qemu-img check ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2 ✓ 10118 | |
| No errors were found on the image. | |
| 54968/1048576 = 5.24% allocated, 0.95% fragmented, 0.00% compressed clusters | |
| Image end offset: 3606183936 | |
| mymac> qemu-img info ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2 ✓ 10138 | |
| image: ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2 | |
| file format: qcow2 | |
| virtual size: 64G (68719476736 bytes) | |
| disk size: 3.4G | |
| cluster_size: 65536 | |
| Format specific information: | |
| compat: 1.1 | |
| lazy refcounts: true | |
| refcount bits: 16 | |
| corrupt: false | |
| # Copy and compress virtual disk to Linux VM folder | |
| qemu-img convert -c -O qcow2 ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/Docker.qcow2 dockermac.qcow2 | |
| # Login into Linux VM | |
| mymac>vagrant ssh | |
| [vagrant@centos7-adb ~]$ ll /vagrant | |
| total 1065220 | |
| -rw-r--r--. 1 qemu qemu 1090781184 Jun 10 12:33 dockermac.qcow2 | |
| -rw-r--r--. 1 vagrant vagrant 2137 Jun 10 12:08 Vagrantfile | |
| # Install libguestfs | |
| [vagrant@centos7-adb ~]$ sudo yum install libguestfs-tools | |
| # Start libguestfs shell | |
| [vagrant@centos7-adb ~]$ sudo guestfish | |
| ><fs> add /vagrant/dockermac.qcow2 # add a copy of Docker for Mac virtual disk | |
| ><fs> run | |
| 100% ⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧ 00:00 | |
| ><fs> list-filesystems | |
| /dev/sda1: swap | |
| /dev/sda2: ext4 | |
| ><fs> mount /dev/sda2 / # mount virtual disk under Linux VM | |
| ><fs> ll / | |
| total 52 | |
| drwxr-xr-x 10 root root 4096 Jun 9 13:29 . | |
| drwxr-xr-x 19 root root 4096 Jun 10 16:17 .. | |
| drwxr-xr-x 4 root root 4096 May 20 20:54 cache | |
| drwxr-xr-x 2 root root 4096 May 6 06:00 empty | |
| drwxr-xr-x 2 root root 4096 May 20 20:54 git | |
| drwxr-xr-x 8 root root 4096 Jun 9 13:29 lib | |
| lrwxrwxrwx 1 root root 9 Jun 9 13:29 lock -> /run/lock | |
| drwxr-xr-x 3 root root 4096 Jun 9 13:29 log | |
| drwx------ 2 root root 16384 Jun 9 13:29 lost+found | |
| lrwxrwxrwx 1 root root 4 Jun 9 13:29 run -> /run | |
| drwxr-xr-x 3 root root 4096 May 6 06:00 spool | |
| drwxrwxrwt 2 root root 4096 May 6 06:00 tmp | |
| ---------- 1 root root 0 Jun 9 13:29 transfused_start.log | |
| # found a container running in Mac | |
| ><fs> ll /lib/docker/containers/45a946cb64d29f7aea8789c710093d494ae07d6bb9dc256ddb5e70e1992be95d/ | |
| total 1016 | |
| drwx------ 3 root root 4096 Jun 9 14:14 . | |
| drwx------ 3 root root 4096 Jun 10 09:46 .. | |
| -rw-r----- 1 root root 1000621 Jun 10 10:06 45a946cb64d29f7aea8789c710093d494ae07d6bb9dc256ddb5e70e1992be95d-json.log | |
| -rw-r--r-- 1 root root 3337 Jun 9 14:14 config.v2.json | |
| -rw-r--r-- 1 root root 1101 Jun 9 14:14 hostconfig.json | |
| -rw-r--r-- 1 root root 13 Jun 9 14:14 hostname | |
| -rw-r--r-- 1 root root 174 Jun 9 14:14 hosts | |
| -rw-r--r-- 1 root root 37 Jun 9 14:14 resolv.conf | |
| -rw------- 1 root root 71 Jun 9 14:14 resolv.conf.hash | |
| drwx------ 2 root root 4096 Jun 9 14:14 shm | |
| [vagrant@centos7-adb ~]$ exit | |
| # Now if you want to shrink virtual disk to save space (e.g. after you cleaned up obsolete images and containers) | |
| # Stop running Docker daemon | |
| mymac> cd ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/ | |
| mymac> mv Docker.qcow2 Docker.qcow2.backup | |
| mymac> qemu-img convert -O qcow2 Docker.qcow2.backup Docker.qcow2 | |
| mymac> qemu-img check Docker.qcow2.backup ✓ 10162 | |
| No errors were found on the image. | |
| 54969/1048576 = 5.24% allocated, 0.96% fragmented, 0.00% compressed clusters | |
| Image end offset: 3606249472 | |
| mymac> qemu-img check Docker.qcow2 ✓ 10163 | |
| No errors were found on the image. | |
| 39636/1048576 = 3.78% allocated, 0.01% fragmented, 0.00% compressed clusters | |
| Image end offset: 2601385984 | |
| # Start your Docker for mac | |
| mymac> /Applications/Docker.app/Contents/Resources/bin/docker-diagnose ✓ 10165 | |
| OS X: version 10.11.5 (build: 15F34) | |
| Docker.app: version: v1.11.1-beta14.5.m | |
| Running diagnostic tests: | |
| [OK] docker-cli | |
| [OK] Moby booted | |
| [OK] driver.amd64-linux | |
| [OK] vmnetd | |
| [OK] osxfs | |
| [OK] db | |
| [OK] slirp | |
| [OK] menubar | |
| [OK] environment | |
| [OK] Docker | |
| [OK] VT-x | |
| Docker logs are being collected into /tmp/20160610-205107.tar.gz | |
| Most specific failure is: No error was detected | |
| # All good! |
Not a lot of science, nevertheless -- learned a new tool and now know where to search and what to do if my local Docker is getting occupy too much disk space.
PS: Special thanks to Richard WM Jones for useful tips about guestfs tools and James Coyle for an article Reclaim disk space from a sparse image file (qcow2/vmdk),
