隐私政策
留言板
金色传说
kubernetes
terraform
云生原
helm
代码编程
Java
Python
Shell
DevOps
Ansible
Gitlab
Jenkins
运维
老司机
Linux 杂锦
Nginx
数据库
elasticsearch
监控
上帝视角
DJI FPV
DJI mini 3 pro
关于本站共计 17093 个字符，预计需要花费 43 分钟才能阅读完成。
重新温习下docker中的文件系统，因为最近有好多pod被evicted，查了kubelet日志是因磁盘满导致
联合文件系统
linux中的联合文件系统UnionFS允许合并一个或多个文件系统目录中的内容，同时保持内容物理隔离。此处主要以OverlayFS展开描述联合挂载
查看当前docker的存储驱动
xadocker@xadocker-virtual-machine:~/Desktop$ docker info --format '{{.Driver}}'
overlay2
此时查看目录/var/lib/docker/overlay2只有一个目录l(字母l)
xadocker@xadocker-virtual-machine:~/Desktop$ sudo ls -l /var/lib/docker/overlay2
total 4
drwx------ 2 root root 4096 8月 20 12:56 l
xadocker@xadocker-virtual-machine:~/Desktop$ sudo ls -l /var/lib/docker/overlay2/l
total 0
拉个镜像下来看看变化
xadocker@xadocker-virtual-machine:~/Desktop$ sudo docker pull nginx:1.14.2
1.14.2: Pulling from library/nginx
27833a3ba0a5: Pull complete
0f23e58bd0b7: Pull complete
8ca774778e85: Pull complete
Digest: sha256:f7988fb6c02e0ce69257d9bd9cf37ae20a60f1df7563c3a2a6abe24160306b8d
Status: Downloaded newer image for nginx:1.14.2
docker.io/library/nginx:1.14.2
查看该镜像的layers信息
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker inspect nginx:1.14.2 | jq -r '.[] | .RootFS'
{
"Type": "layers",
"Layers": [
"sha256:5dacd731af1b0386ead06c8b1feff9f65d9e0bdfec032d2cd0bc03690698feda",
"sha256:b8f18c3b860b067be09836beadd676a0aa1e784ec28cf730986859b4146c344a",
"sha256:82ae01d5004e2143b642b1a008624e7521c73ab18e5776a22f18a172b9dbec80"
]
}可以看到layers有三层，而此时的/var/lib/docker/overlay2目录存在以下内容
root@xadocker-virtual-machine:/var/lib/docker/overlay2# tree -L 2
.
├── 0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33
│ ├── committed
│ ├── diff
│ └── link
├── 43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9
│ ├── committed
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
├── 441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
└── l
├── GHJM6TNXCEPVQCFQSKRJ7YHQXH -> ../43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff
├── OU3ZI5MET46OMFNFWPEEHCW47X -> ../0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff
└── U4BVMECOSCTSWIUQ5WWS4TY7MN -> ../441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/diff
其中没有lower的则为镜像的基层，因为lower记录着其父级层信息内容
root@xadocker-virtual-machine:/var/lib/docker/overlay2# cat 43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/lower
l/OU3ZI5MET46OMFNFWPEEHCW47X而diff内容则是代表当前层的内容
# 基层diff目录
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ls 0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff/
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
# 非基层diff目录
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ls 43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff/
etc lib tmp usr var
此时我们看下镜像的GraphDriver信息
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker inspect nginx:1.14.2 | jq -r '.[] | .GraphDriver'
{
"Data": {
"LowerDir": "/var/lib/docker/overlay2/43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff:/var/lib/docker/overlay2/0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff",
"MergedDir": "/var/lib/docker/overlay2/441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/merged",
"UpperDir": "/var/lib/docker/overlay2/441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/diff",
"WorkDir": "/var/lib/docker/overlay2/441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/work"
},
"Name": "overlay2"
}
从上面信息可以看到有以下4个目录
- LowerDir：包含镜像层的除当前层（最上层）diff
- UpperDir：指向当前镜像当前层（最上层）diff
- WorkDir：官方说供OverlayFS内部使用
- MergedDir：包含所有层的联合挂载内容
但是从前面的目录信息来看，并没有发现有MergedDir，因为该层是容器运行后的对LowerDir和UpperDir的联合挂载点，目前没启动容器所以没有
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker create --name test-nginx nginx:1.14.2
a1b587358364ee26e11b52e30bcc9febc89c89612cb6ded972c5d6a6f0a16384
root@xadocker-virtual-machine:/var/lib/docker/overlay2# tree -L 2
.
├── 0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33
│ ├── committed
│ ├── diff
│ └── link
├── 43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9
│ ├── committed
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
├── 441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e
│ ├── committed
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
├── 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
├── 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init
│ ├── committed
│ ├── diff
│ ├── link
│ ├── lower
│ └── work
└── l
├── A42HGWMUAQXXX7PJCXEY4BA46H -> ../541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff
├── GHJM6TNXCEPVQCFQSKRJ7YHQXH -> ../43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff
├── HOHSUFEKJXNVVCJSZWJSAYRDS2 -> ../541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/diff
├── OU3ZI5MET46OMFNFWPEEHCW47X -> ../0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff
└── U4BVMECOSCTSWIUQ5WWS4TY7MN -> ../441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/diff
20 directories, 13 files
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker inspect test-nginx | jq -r '.[]| .GraphDriver'
{
"Data": {
"LowerDir": "/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff:/var/lib/docker/overlay2/441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/diff:/var/lib/docker/overlay2/43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff:/var/lib/docker/overlay2/0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff",
"MergedDir": "/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/merged",
"UpperDir": "/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/diff",
"WorkDir": "/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/work"
},
"Name": "overlay2"
}
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ll 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff/etc/
total 8
drwxr-xr-x 2 root root 4096 8月 20 13:52 ./
drwxr-xr-x 4 root root 4096 8月 20 13:52 ../
-rwxr-xr-x 1 root root 0 8月 20 13:52 hostname*
-rwxr-xr-x 1 root root 0 8月 20 13:52 hosts*
lrwxrwxrwx 1 root root 12 8月 20 13:52 mtab -> /proc/mounts
-rwxr-xr-x 1 root root 0 8月 20 13:52 resolv.conf*
# hostname、hosts、resolv.conf都为空的内容
root@xadocker-virtual-machine:/var/lib/docker/overlay2# cat 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff/etc/hostname
root@xadocker-virtual-machine:/var/lib/docker/overlay2# cat 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff/etc/hosts
root@xadocker-virtual-machine:/var/lib/docker/overlay2# cat 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init/diff/etc/resolv.conf
从上面可以看到create容器时会生成两个目录，其中一个带init后缀，搜索一通后说该层只是用来初始化一些配置的如hostname,dns解析等，当我们用命令去配置hostname和dns解析时就是在该层去操作配置，其实就是引入中间init层来做初始化配置的修改
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker create --name nginx-test2-xad --hostname nginx-test2-hostname --add-host nginx.xadocker.cn:192.168.44.168 --dns 223.5.5.5 nginx:1.14.2但是通过上面命令创建该容器后但其init目录里的文件信息还是空的，inspect后发现hosts/hostname/resolv.conf却在/var/lib/docker/container内，暂未发现这层的关系，先埋个坑咯~
此时再创建一个容器并查看信息
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker create --name test-nginx-2 nginx:1.14.2
4ca89f3e1b0ace54dcde604eadbf5a430fd5d02e64f1d6f056f261b90ba5c349
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ls -lrt
total 32
drwx--x--- 3 root root 4096 8月 20 12:58 0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33
drwx--x--- 4 root root 4096 8月 20 12:58 43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9
drwx--x--- 4 root root 4096 8月 20 13:52 441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e
drwx--x--- 4 root root 4096 8月 20 13:52 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada-init
drwx--x--- 4 root root 4096 8月 20 13:52 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada
drwx------ 2 root root 4096 8月 20 14:07 l
drwx--x--- 4 root root 4096 8月 20 14:07 3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4-init
drwx--x--- 4 root root 4096 8月 20 14:07 3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker inspect test-nginx-2 | jq -r '.[]| .GraphDriver'
{
"Data": {
"LowerDir": "/var/lib/docker/overlay2/3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4-init/diff:/var/lib/docker/overlay2/441adc17b9c104687e6d9ea8224b8da74489542a303ae64c78e9e9243194777e/diff:/var/lib/docker/overlay2/43c54c31282405e68e577d9edcfc572e695cd71aabc6193123e9676da14970d9/diff:/var/lib/docker/overlay2/0ee4b77a1e8f6c374e4974182bf850036680b3bccecbc05d4d206373cd943a33/diff",
"MergedDir": "/var/lib/docker/overlay2/3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4/merged",
"UpperDir": "/var/lib/docker/overlay2/3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4/diff",
"WorkDir": "/var/lib/docker/overlay2/3a757b7e83a308c49c22c2b493f40ed393ae015fc6b6fd7404ff74026a1e03d4/work"
},
"Name": "overlay2"
}
可以看到此时create的容器test-nginx和test-nginx-2是复用了镜像层，这样可以实现节约磁盘的使用，现在尝试将test-nginx启动看看
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
4ca89f3e1b0a nginx:1.14.2 "nginx -g 'daemon of…" 4 minutes ago Created test-nginx-2
a1b587358364 nginx:1.14.2 "nginx -g 'daemon of…" 19 minutes ago Created test-nginx
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker start test-nginx
test-nginx
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker ps -a
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
4ca89f3e1b0a nginx:1.14.2 "nginx -g 'daemon of…" 4 minutes ago Created test-nginx-2
a1b587358364 nginx:1.14.2 "nginx -g 'daemon of…" 19 minutes ago Up 1 second 80/tcp test-nginx此时再查看该容器目录就会有一个merged目录了，该目录内容和我们进入到容器里的看到的内容一致
root@xadocker-virtual-machine:/var/lib/docker/overlay2# tree 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada -L 1
541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada
├── diff
├── link
├── lower
├── merged
└── work
3 directories, 2 files
# 查看挂载信息
root@xadocker-virtual-machine:/var/lib/docker/overlay2# mount | grep over
overlay on /var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/merged type overlay (rw,relatime,lowerdir=/var/lib/docker/overlay2/l/A42HGWMUAQXXX7PJCXEY4BA46H:/var/lib/docker/overlay2/l/U4BVMECOSCTSWIUQ5WWS4TY7MN:/var/lib/docker/overlay2/l/GHJM6TNXCEPVQCFQSKRJ7YHQXH:/var/lib/docker/overlay2/l/OU3ZI5MET46OMFNFWPEEHCW47X,upperdir=/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/diff,workdir=/var/lib/docker/overlay2/541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/work)
# 该目录和我们进入到容器里查看的目录
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ls 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/merged/
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker exec -it test-nginx ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker exec -it test-nginx cat /etc/hostname
a1b587358364
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker exec -it test-nginx cat /etc/hosts
127.0.0.1 localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.17.0.2 a1b587358364
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker exec -it test-nginx cat /etc/resolv.conf
# This file is managed by man:systemd-resolved(8). Do not edit.
#
# This is a dynamic resolv.conf file for connecting local clients directly to
# all known uplink DNS servers. This file lists all configured search domains.
#
# Third party programs must not access this file directly, but only through the
# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,
# replace this symlink by a static file or a different symlink.
#
# See man:systemd-resolved.service(8) for details about the supported modes of
# operation for /etc/resolv.conf.
nameserver 192.168.44.2
search localdomain
但是当我们停止容器时，merged目录就会消失，并不代表着内容丢失，因为diff内会记录着该层的变化，merged只是联合挂载后内容
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker exec -it test-nginx bash
root@a1b587358364:/# ls /tmp/
root@a1b587358364:/# echo hello >> /tmp/test.txt
root@a1b587358364:/# exit
exit
root@xadocker-virtual-machine:/var/lib/docker/overlay2# docker stop test-nginx
test-nginx
root@xadocker-virtual-machine:/var/lib/docker/overlay2# ls 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada
diff link lower work
root@xadocker-virtual-machine:/var/lib/docker/overlay2# cat 541c581d71c636420217bcc4b7a699a445c924de01fe7adf4dc40e68a1806ada/diff/tmp/test.txt
hello容器是如何读写overlay2的呢？
读取文件
考虑容器打开文件以通过覆盖进行读取访问的三种场景。
- 该文件不存在于容器层中：如果容器打开一个文件进行读取访问，并且该文件尚不存在于容器 (
upperdir) 中，则会从映像 (lowerdir) 中读取该文件。这会产生非常小的性能开销 - 文件只存在于容器层：如果容器打开一个文件进行读访问，并且该文件存在于容器（
upperdir）中而不是镜像（lowerdir）中，则直接从容器中读取 - 文件同时存在于容器层和镜像层：如果容器打开一个文件进行读访问，并且该文件存在于镜像层和容器层，则读取该文件在容器层的版本。容器层（
upperdir）中的文件掩盖了镜像层中的同名文件lowerdir
修改文件或目录
- 首次写入文件：容器首次写入现有文件时，该文件在容器中不存在 (
upperdir)。驱动程序overlay2执行copy_up操作以将文件从映像 (lowerdir) 复制到容器 (upperdir)。然后，容器将更改写入容器层中文件的新副本。然而，OverlayFS 在文件级别而不是块级别工作。这意味着所有 OverlayFS copy_up 操作都会复制整个文件，即使文件非常大并且只修改了其中的一小部分。这会对容器写入性能产生显着影响。然而，有两件事值得注意：- copy_up 操作仅在第一次写入给定文件时发生。对同一文件的后续写入将针对已复制到容器的文件副本进行操作
- OverlayFS 适用于多个层。这意味着在具有多层的图像中搜索文件时，性能可能会受到影响
- 删除文件和目录：
- 当删除容器内的文件时，会在容器中创建一个空白
upperdir文件 。图像层中的文件版本lowerdir不会被删除（因为它lowerdir是只读的）。但是，whiteout 文件会阻止容器使用它。 - 当删除容器内的目录时，会在容器内创建一个不透明目录
upperdir。这与whiteout文件的工作方式相同，并且有效地防止目录被访问，即使它仍然存在于图像中(lowerdir)
- 当删除容器内的文件时，会在容器中创建一个空白
- 重命名目录：
rename只有源路径和目标路径都在顶层时才允许调用目录。否则，它将返回EXDEV错误（“不允许跨设备链接”）。您的应用程序需要设计为处理EXDEV和回退到“复制和取消链接”策略
统计POD中容器的增量文件大小
从上面的一些简单说明可以了解到upperdir即为容器的增量内容，所以我们可以分别统计下k8s pod中看看谁占的多
[root@master-192-168-31-100 workdir]# cat get-docker-upperdir.sh
#!/bin/bash
docker inspect `docker ps -q` | jq -r '.[] | [.Config.Labels["io.kubernetes.pod.namespace"],.Config.Labels["io.kubernetes.pod.name"],.Config.Labels["io.kubernetes.container.name"], .GraphDriver.Data.UpperDir] | @tsv' | \
while read line
do
echo -n $line" "
echo $line | awk '{print $4}' | xargs du -sk | awk '{print $1}'
done
# 执行
[root@master-192-168-31-100 workdir]# bash get-docker-upperdir.sh | column -t
tigera-operator tigera-operator-66f6445597-7h2q9 tigera-operator /var/lib/docker/overlay2/721b82301cd351ad27a8d0c00ee32dd3ebdbcfc2cfe0ef695b11902356e650e5/diff 0
calico-apiserver calico-apiserver-868f4c547b-t9tkw calico-apiserver /var/lib/docker/overlay2/8178c649017efb057411f174ba7ba395f37cc4025269c64a2f8347ea6a061062/diff 0
calico-apiserver calico-apiserver-868f4c547b-t9tkw POD /var/lib/docker/overlay2/639f27b12febc2b1652db14174128ecea6daaa08ccc843bb65970d0e65eb1cb8/diff 0
kube-system coredns-7d75679df-prvsb coredns /var/lib/docker/overlay2/b324209e3fdaaabb20df39f9ff2502c1b7c1926c51b942240ae4cecb684f88c7/diff 0
calico-system calico-kube-controllers-77b99b58ff-jfkk7 calico-kube-controllers /var/lib/docker/overlay2/954ff02124ea07d5d4134e34bd84cd26f168e49ac3875f161aa08861a35f128f/diff 4其实到这里我们才拿到POD容器里的upperdir增量内容，但还有一部分存储是在POD里的emptydir或者hostpath内，这种类型的volume也是霍霍宿主机硬盘的帮凶
对于emptydir，会在pod的目录中生成并挂在到容器里，pod目录在/var/lib/kubelet/pods/中对应的POD ID里
[root@master-192-168-31-100 workdir]# ll /var/lib/kubelet/pods/
总用量 0
drwxr-x--- 5 root root 71 8月 25 22:49 087f6929-223f-4605-b6ef-5afa8719fc78
drwxr-x--- 5 root root 71 8月 25 23:19 182e216a-3608-45c3-8813-b2fd71b99d68
drwxr-x--- 5 root root 71 8月 25 22:49 225b47362d283e421361cb0d30e95081
drwxr-x--- 5 root root 71 8月 25 23:20 3df101f9-636f-4df4-bd59-4c77811babe3
drwxr-x--- 5 root root 71 8月 25 23:20 4e8507c3-6f07-4e49-83bb-9c97292cdb77
# 一个demo测试样例
[root@master-192-168-31-100 workdir]# cat nginx-test.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
name: my-deployment
spec:
replicas: 2
selector:
matchLabels:
app: my-app
template:
metadata:
labels:
app: my-app
spec:
containers:
- name: my-container
image: nginx:latest
ports:
- containerPort: 80
volumeMounts:
- name: my-emptydir
mountPath: /data # 这里指定挂载路径
volumes:
- name: my-emptydir
emptyDir: {} # 这里配置 EmptyDir 卷在emptydir中创建测试文件测试下
root@master-192-168-31-100 workdir]# kubectl exec -it my-deployment-87fcddd69-rf9qm -- bash
root@my-deployment-87fcddd69-rf9qm:/data# dd if=/dev/zero of=/data/test.db bs=1M count=1024
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 0.743424 s, 1.4 GB/s定位到该pod目录内可以看到一个empty-dir后缀的目录
[root@node-192-168-31-102 ~]# tree /var/lib/kubelet/pods/aae19680-6f64-4c56-9725-9494bf8ac8ee/volumes/kubernetes.io~empty-dir/
/var/lib/kubelet/pods/aae19680-6f64-4c56-9725-9494bf8ac8ee/volumes/kubernetes.io~empty-dir/
└── my-emptydir
└── test.db
1 directory, 1 file但是我们去这个容器的upperdir中可以看到emptydir的挂载点对应的data目录，但是其内容为空，因为容器挂载时会在容器里创建这个名字的目录（所以upperdir里有），但是一旦容器启动后，就被volume覆盖遮住了
[root@node-192-168-31-102 ~]# tree /var/lib/docker/overlay2/be6b4cebf42bdd14c525f446706d39298fdaa8476e723d3acf7527a11737db61/diff/data/
/var/lib/docker/overlay2/be6b4cebf42bdd14c525f446706d39298fdaa8476e723d3acf7527a11737db61/diff/data/
0 directories, 0 files
# 查看对应的目录id
[root@master-192-168-31-100 workdir]# kubectl exec -it my-deployment-87fcddd69-rf9qm -- ls -lid /data
202980633 drwxrwxrwx 2 root root 21 Aug 26 16:25 /data
[root@node-192-168-31-102 ~]# ll -di /var/lib/docker/overlay2/be6b4cebf42bdd14c525f446706d39298fdaa8476e723d3acf7527a11737db61/diff/data/
68731756 drwxr-xr-x 2 root root 6 8月 27 00:22 /var/lib/docker/overlay2/be6b4cebf42bdd14c525f446706d39298fdaa8476e723d3acf7527a11737db61/diff/data/
[root@node-192-168-31-102 ~]# ll -di /var/lib/kubelet/pods/aae19680-6f64-4c56-9725-9494bf8ac8ee/volumes/kubernetes.io~empty-dir/my-emptydir/
202980633 drwxrwxrwx 2 root root 21 8月 27 00:25 /var/lib/kubelet/pods/aae19680-6f64-4c56-9725-9494bf8ac8ee/volumes/kubernetes.io~empty-dir/my-emptydir/看来只能获取pod目录里的emptydir了，先获取POD ID，在去定位emptydir就够了，这里就略了。而对于hostpath类型，则不会在pod目录里创建，而是自行定义的路径了，不解析pod的spec的情况下，好像只能从docker的mounts里获取了，略
正文完
