阅读完 James Coyle 的博客 后,我发现我需要使用 docker save
和 docker load
命令。
> docker images
REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
progrium/consul latest e9fe5db22401 11 days ago 25.81 MB
> docker save e9fe5db22401 | tar x
> ls e9fe5db22401*
VERSION json layer.tar
VERSION
文件中只包含1.0
,而json
文件包含了相当多的信息:
{
"id": "e9fe5db224015ddfa5ee9dbe43b414ecee1f3108fb6ed91add11d2f506beabff",
"parent": "68f9e4929a4152df9b79d0a44eeda042b5555fbd30a36f98ab425780c8d692eb",
"created": "2014-08-20T17:54:30.98176344Z",
"container": "3878e7e9b9935b7a1988cb3ebe9cd45150ea4b09768fc1af54e79b224bf35f26",
"container_config": {
"Hostname": "7f17ad58b5b8",
"Domainname": "",
"User": "",
"Memory": 0,
"MemorySwap": 0,
"CpuShares": 0,
"Cpuset": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"PortSpecs": null,
"ExposedPorts": {
"53/udp": {},
"8300/tcp": {},
"8301/tcp": {},
"8301/udp": {},
"8302/tcp": {},
"8302/udp": {},
"8400/tcp": {},
"8500/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"HOME=/",
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"SHELL=/bin/bash"
],
"Cmd": [
"/bin/sh",
"-c",
"#(nop) CMD []"
],
"Image": "68f9e4929a4152df9b79d0a44eeda042b5555fbd30a36f98ab425780c8d692eb",
"Volumes": {
"/data": {}
},
"WorkingDir": "",
"Entrypoint": [
"/bin/start"
],
"NetworkDisabled": false,
"OnBuild": [
"ADD ./config /config/"
]
},
"docker_version": "1.1.2",
"author": "Jeff Lindsay <progrium@gmail.com>",
"config": {
"Hostname": "7f17ad58b5b8",
"Domainname": "",
"User": "",
"Memory": 0,
"MemorySwap": 0,
"CpuShares": 0,
"Cpuset": "",
"AttachStdin": false,
"AttachStdout": false,
"AttachStderr": false,
"PortSpecs": null,
"ExposedPorts": {
"53/udp": {},
"8300/tcp": {},
"8301/tcp": {},
"8301/udp": {},
"8302/tcp": {},
"8302/udp": {},
"8400/tcp": {},
"8500/tcp": {}
},
"Tty": false,
"OpenStdin": false,
"StdinOnce": false,
"Env": [
"HOME=/",
"PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
"SHELL=/bin/bash"
],
"Cmd": [],
"Image": "68f9e4929a4152df9b79d0a44eeda042b5555fbd30a36f98ab425780c8d692eb",
"Volumes": {
"/data": {}
},
"WorkingDir": "",
"Entrypoint": [
"/bin/start"
],
"NetworkDisabled": false,
"OnBuild": [
"ADD ./config /config/"
]
},
"architecture": "amd64",
"os": "linux",
"Size": 0
}
layer.tar
文件似乎是空的。于是检查了它的父文件夹和祖父文件夹,发现它们的 layer.tar
文件中都没有文件。
因此假设 4.0K 是一个空 tarball 的标准大小:
for layer in $(du -hs */layer.tar | grep -v 4.0K | cut -f2)
do (echo $layer:;tar tvf $layer)
done
这些变化对文件系统进行了简单的增量更改。
所以一个结论是,最好只使用Docker构建图像并将其推送到注册表,就像Packer一样。
从头开始构建镜像的方法在文档中描述。
事实证明,docker import - scratch
并不关心tarball中的内容,它只假设那是rootfs。
> touch foo
> tar c foo | docker import - scratch
02bb6cd70aa2c9fbaba37c8031c7412272d804d50b2ec608e14db054fc0b9fab
> docker save 02bb6cd70aa2c9fbaba37c8031c7412272d804d50b2ec608e14db054fc0b9fab | tar x
> ls 02bb6cd70aa2c9fbaba37c8031c7412272d804d50b2ec608e14db054fc0b9fab/
VERSION json layer.tar
> tar tvf 02bb6cd70aa2c9fbaba37c8031c7412272d804d50b2ec608e14db054fc0b9fab/layer.tar
drwxr-xr-x 0/0 0 2014-09-01 13:46 ./
-rw-r--r-- 500/500 0 2014-09-01 13:46 foo
对于OpenEmbedded集成,最好构建rootfs
tar包,这是Yocto开箱即用提供的功能,并使用官方Python库使用import_image(src='rootfs.tar', repository='scratch')
导入rootfs
tar包并使用私有注册表方法推送。
这可能不是最优雅的解决方案,但目前只能这样操作。否则,可以以自己的方式管理和部署rootfs
修订版本,并在目标主机上使用docker import
,尽管这仍然不完美,但相对比较简单。