一、docker容器的结构
containerd 是老大，新建一个容器会先新建 containerd-shim，containerd-shim 会建出来最终的docker容器。
1、 查看containerd的pid
pidof containerd == 2841
2、 查看 父进程是containerd的进程，全是 containerd-shim
ps -A -ostat,pid,ppid,user,cmd|grep 2841
Ssl 2841 1 root /usr/bin/containerd
Sl 7320 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/52eeb71ffa22cd8020a6214fa1a556c2e22c3012858a75aa5799b021502916e1 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
Sl 7342 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/08bcf4df1a2072dc69f825517c6c1ace3ed81886d420fe974fc0683ae61aa7fb -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
Sl 8087 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/c3d3530cf2f5dddff0d1a37c5cd6791ffb15cf21d5e1096d96ca36269e077136 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
Sl 19039 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/63ee2df4c255110248842e885fb0b9dafca9791dda6a00499bbc3fc99e153743 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
Sl 19338 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
Sl 19407 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
3、 查看一个containerd-shim 和子进程
# 这是一个 nginx容器
ps -A -opid,ppid,user,cmd |grep 7320
7320 2841 root containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/52eeb71ffa22cd8020a6214fa1a556c2e22c3012858a75aa5799b021502916e1 -address /run/containerd/containerd.sock -containerd-binary /usr/bin/containerd -runtime-root /var/run/docker/runtime-runc
7337 7320 root nginx: master process nginx -g daemon off;
4、查看这个nginx的容器
# docker ps |grep 52eeb71ffa
52eeb71ffa22 xxxx/xxxx/safe-nginx "nginx -g 'daemon of…" 41 hours ago Up 41 hours k8s_safe-nginx_668c459d6-pp7bxxx-xxxx_4e11582d-aeea-11ea-8af4-0050569e47b9_0
二、 pod与容器，cgroup
1、systemctl status && systemd-cgls
在不加最后的unit参数的时候，这个命名变得很陌生了。主要是查看 cgroup状态。
[root@my-node1 ~]# systemctl status
● my-node1
State: running
Jobs: 0 queued
Failed: 0 units
Since: 一 2020-06-15 16:48:44 CST; 1 day 17h ago
CGroup: /
├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
├─kubepods
│ ├─besteffort
│ │ └─podf86494f1-aeea-11ea-8af4-0050569e47b9
│ │ ├─167e38f31f6f225fe7e53a6fc31a1aebb85628531b6b3b438a3591fffefca93c
│ │ │ └─kube-proxy
│ │ │ └─6227 /usr/local/bin/kube-proxy --config=/var/lib/kube-proxy/config.conf --hostname-override=my-node1
│ │ └─1ff0ae01463af951a16ac8e7006ec99333e8a42578118791529755b5704de4cb
│ │ └─5982 /pause
│ └─burstable
│ ├─podf5f16f15-af9e-11ea-8af4-0050569e47b9
│ │ ├─d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
│ │ │ ├─19431 nginx: master process nginx -g daemon off
│ │ │ ├─19453 nginx: worker proces
│ │ │ ├─19454 nginx: worker proces
│ │ │ ├─19455 nginx: worker proces
│ │ │ ├─19456 nginx: worker proces
│ │ │ ├─19457 nginx: worker proces
│ │ │ ├─19458 nginx: worker proces
│ │ │ ├─19459 nginx: worker proces
│ │ │ └─19460 nginx: worker proces
│ │ ├─9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
│ │ │ └─19356 redis-server
│ │ └─63ee2df4c255110248842e885fb0b9dafca9791dda6a00499bbc3fc99e153743
│ │ └─19057 /pause
│ ├─pod4e11582d-aeea-11ea-8af4-0050569e47b9
│ │ ├─52eeb71ffa22cd8020a6214fa1a556c2e22c3012858a75aa5799b021502916e1
│ │ │ ├─7337 nginx: master process nginx -g daemon off
│ │ │ ├─7380 nginx: worker proces
│ │ │ ├─7381 nginx: worker proces
│ │ │ ├─7382 nginx: worker proces
│ │ │ ├─7383 nginx: worker proces
│ │ │ ├─7384 nginx: worker proces
│ │ │ ├─7385 nginx: worker proces
│ │ │ ├─7386 nginx: worker proces
│ │ │ └─7387 nginx: worker proces
│ │ └─0a5529d9b0fcb544630ea2722c8a82feaa8c3d2efd7ea4118bc5713ffa604437
│ │ └─7175 /pause
│ ├─podf8697bea-aeea-11ea-8af4-0050569e47b9
│ │ ├─99e0fbfa76ad0141bce359555fa343380a0c27b8a441609b9fe41beed954eda4
│ │ │ ├─6962 /bin/sh /install-cni.sh
│ │ │ └─7233 sleep 3600
│ │ ├─1ac5b03e0a9683313a409330a0c7390ea908d963ec9955ff71d2739882924c2d
│ │ │ └─6593 /opt/bin/flanneld --ip-masq --kube-subnet-mgr
│ │ └─dcbc2486a119dac68cb6bb2b90941411927c27a0a58c9027475026d02b83e224
│ │ └─5967 /pause
│ └─podf8662a28-aeea-11ea-8af4-0050569e47b9
│ ├─599b533be6646195bc24f5d32bf2551a131a207fd469522608fe7916b187c7cc
│ │ └─7049 ./kube-rbac-proxy --logtostderr --secure-listen-address=11.11.176.68:9100 --tls-cipher-suites=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256,TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256,TLS_RSA_
│ ├─a18a4606e095579037d4e7f10276b64ab020abf76472598c39acfa67cd16b0f2
│ │ └─6715 /bin/node_exporter --web.listen-address=127.0.0.1:9100 --path.procfs=/host/proc --path.sysfs=/host/sys --path.rootfs=/host/root --collector.textfile.directory=/host/key --collector
│ └─aa8c844c2907348c09244c240927964494ab1a43181c1e2cd1e8154e4451bb78
│ └─5974 /pause
├─user.slice
│ └─user-0.slice
│ ├─session-290.scope
│ │ ├─11908 systemctl status
│ │ ├─11909 less
│ │ ├─31551 sshd: root@pts/1
│ │ └─31579 -bash
│ ├─session-175.scope
│ │ ├─30428 sshd: root@pts/0
│ │ └─30430 -bash
│ └─session-1.scope
│ ├─1348 login -- root
│ ├─1352 -bash
│ └─1448 bash
└─system.slice
├─rpc-statd.service
│ └─7519 /usr/sbin/rpc.statd
├─kubelet.service
│ └─5773 /usr/local/sbin/kubelet --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf --kubeconfig=/etc/kubernetes/kubelet.conf --pod-manifest-path=/etc/kubernetes/manifests --allow-pr
├─docker.service
│ └─2842 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sock
├─containerd.service
│ ├─ 2841 /usr/bin/containerd
│ ├─ 5914 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/dcbc2486a119dac68cb6bb2b90941411927c27a0a58c9027475026d02b83e224 -address /run/contain
│ ├─ 5918 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/aa8c844c2907348c09244c240927964494ab1a43181c1e2cd1e8154e4451bb78 -address /run/contain
│ ├─ 5929 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/1ff0ae01463af951a16ac8e7006ec99333e8a42578118791529755b5704de4cb -address /run/contain
│ ├─ 6210 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/167e38f31f6f225fe7e53a6fc31a1aebb85628531b6b3b438a3591fffefca93c -address /run/contain
│ ├─ 6575 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/1ac5b03e0a9683313a409330a0c7390ea908d963ec9955ff71d2739882924c2d -address /run/contain
│ ├─ 6698 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/a18a4606e095579037d4e7f10276b64ab020abf76472598c39acfa67cd16b0f2 -address /run/contain
│ ├─ 6944 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/99e0fbfa76ad0141bce359555fa343380a0c27b8a441609b9fe41beed954eda4 -address /run/contain
│ ├─ 7031 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/599b533be6646195bc24f5d32bf2551a131a207fd469522608fe7916b187c7cc -address /run/contain
│ ├─ 7156 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/0a5529d9b0fcb544630ea2722c8a82feaa8c3d2efd7ea4118bc5713ffa604437 -address /run/contain
│ ├─ 7320 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/52eeb71ffa22cd8020a6214fa1a556c2e22c3012858a75aa5799b021502916e1 -address /run/contain
│ ├─ 7342 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/08bcf4df1a2072dc69f825517c6c1ace3ed81886d420fe974fc0683ae61aa7fb -address /run/contain
│ ├─ 8087 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/c3d3530cf2f5dddff0d1a37c5cd6791ffb15cf21d5e1096d96ca36269e077136 -address /run/contain
│ ├─19039 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/63ee2df4c255110248842e885fb0b9dafca9791dda6a00499bbc3fc99e153743 -address /run/contain
│ ├─19338 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94 -address /run/contain
│ └─19407 containerd-shim -namespace moby -workdir /var/lib/containerd/io.containerd.runtime.v1.linux/moby/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a -address /run/contain
├─nkucsd.service
│ └─1042 nkucsd
├─sshd.service
│ └─1025 /usr/sbin/sshd -D
├─postfix.service
│ ├─1272 /usr/libexec/postfix/master -w
│ ├─1274 qmgr -l -t unix -u
│ └─5409 pickup -l -t unix -u
├─tuned.service
│ └─1023 /usr/bin/python -Es /usr/sbin/tuned -l -P
├─crond.service
│ └─731 /usr/sbin/crond -n
├─NetworkManager.service
│ └─717 /usr/sbin/NetworkManager --no-daemon
├─vmtoolsd.service
│ └─716 /usr/bin/vmtoolsd
├─vgauthd.service
│ └─715 /usr/bin/VGAuthService -s
├─rsyslog.service
│ └─710 /usr/sbin/rsyslogd -n
├─gssproxy.service
│ └─719 /usr/sbin/gssproxy -D
├─polkit.service
│ └─707 /usr/lib/polkit-1/polkitd --no-debug
├─chronyd.service
│ └─713 /usr/sbin/chronyd
├─dbus.service
│ └─700 /bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation
├─irqbalance.service
│ └─699 /usr/sbin/irqbalance --foreground
├─systemd-logind.service
│ └─697 /usr/lib/systemd/systemd-logind
├─rpcbind.service
│ └─703 /sbin/rpcbind -w
├─auditd.service
│ └─673 /sbin/auditd
├─systemd-udevd.service
│ └─541 /usr/lib/systemd/systemd-udevd
├─lvm2-lvmetad.service
│ └─531 /usr/sbin/lvmetad -f
└─systemd-journald.service
└─513 /usr/lib/systemd/systemd-journald
2、从目录里看 cgroup
# ll /sys/fs/cgroup
总用量 0
drwxr-xr-x 6 root root 0 4月 25 2019 blkio
lrwxrwxrwx 1 root root 11 4月 25 2019 cpu -> cpu,cpuacct
lrwxrwxrwx 1 root root 11 4月 25 2019 cpuacct -> cpu,cpuacct
drwxr-xr-x 6 root root 0 4月 25 2019 cpu,cpuacct
drwxr-xr-x 4 root root 0 4月 25 2019 cpuset
drwxr-xr-x 6 root root 0 4月 25 2019 devices
drwxr-xr-x 4 root root 0 4月 25 2019 freezer
drwxr-xr-x 4 root root 0 4月 25 2019 hugetlb
drwxr-xr-x 6 root root 0 4月 25 2019 memory
lrwxrwxrwx 1 root root 16 4月 25 2019 net_cls -> net_cls,net_prio
drwxr-xr-x 4 root root 0 4月 25 2019 net_cls,net_prio
lrwxrwxrwx 1 root root 16 4月 25 2019 net_prio -> net_cls,net_prio
drwxr-xr-x 4 root root 0 4月 25 2019 perf_event
drwxr-xr-x 4 root root 0 4月 25 2019 pids
drwxr-xr-x 6 root root 0 4月 25 2019 systemd
## 在 /sys/fs/cgroup/systemd 这个目录就是 systemd-cgls 展示的根。
3、只看我这一个pod
我起了一个 pod 里边有一个nginx和一个redis，还有一个pause。
CGroup: /
├─1 /usr/lib/systemd/systemd --switched-root --system --deserialize 21
├─kubepods ### pod的根cgroup
│ └─burstable ### pod根据request和limit分为3个保证稳定性的QoS服务质量级别：BestEffort，Burstable，Guaranteed；参考：https://blog.csdn.net/horsefoot/article/details/52091077
│ ├─podf5f16f15-af9e-11ea-8af4-0050569e47b9 ### 对应于 /var/lib/kubelet/pods/xxxx ，其下的目录： containers etc-hosts plugins volumes
│ │ ├─d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a ### nginx 容器的id
│ │ │ ├─19431 nginx: master process nginx -g daemon off
│ │ │ ├─19453 nginx: worker proces
│ │ │ ├─19454 nginx: worker proces
│ │ │ ├─19455 nginx: worker proces
│ │ │ ├─19456 nginx: worker proces
│ │ │ ├─19457 nginx: worker proces
│ │ │ ├─19458 nginx: worker proces
│ │ │ ├─19459 nginx: worker proces
│ │ │ └─19460 nginx: worker proces
│ │ ├─9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94 ### redis 容器的id
│ │ │ └─19356 redis-server
│ │ └─63ee2df4c255110248842e885fb0b9dafca9791dda6a00499bbc3fc99e153743 ### pause 容器的id
│ │ └─19057 /pause
# cat /proc/`pidof nginx`/cgroup
11:memory:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
10:cpuset:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
9:devices:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
8:blkio:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
7:net_prio,net_cls:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
6:perf_event:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
5:pids:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
4:cpuacct,cpu:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
3:hugetlb:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
2:freezer:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
1:name=systemd:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/d62b4a22abd21d47636a1c84e970ad7e76d8fe633232715f74606ee93c71291a
# cat /proc/`pidof redis-server`/cgroup
# cat /proc/19356/cgroup
11:memory:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
10:cpuset:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
9:devices:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
8:blkio:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
7:net_prio,net_cls:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
6:perf_event:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
5:pids:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
4:cpuacct,cpu:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
3:hugetlb:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
2:freezer:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
1:name=systemd:/kubepods/burstable/podf5f16f15-af9e-11ea-8af4-0050569e47b9/9934ac36efade11bde691c12729a1dfa7483b8864ae4ded7a77a03f3b6e84d94
三、 pod和容器，namespace
就是pause和容器，查看pause进程和容器进程的namespace关系
首先要从容器 id 获得其进程在宿主机上的进程号：
1、查看pause容器的进程号： 19057
# docker top 63ee2df4
UID PID PPID C STIME TTY TIME CMD
root 19057 19039 0 Jun16 ? 00:00:00 /pause
2、 查看 redis容器的进程号：19356
# docker top 9934ac36
UID PID PPID C STIME TTY TIME CMD
100 19356 19338 0 Jun16 ? 00:03:21 redis-server
3、 查看 nginx容器的进程号：19431
# docker top d62b4a2
UID PID PPID C STIME TTY TIME CMD
root 19431 19407 0 Jun16 ? 00:00:00 nginx: master process nginx -g daemon off;
100 19453 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19454 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19455 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19456 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19457 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19458 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19459 19431 0 Jun16 ? 00:00:00 nginx: worker process
100 19460 19431 0 Jun16 ? 00:00:00 nginx: worker process
4、 查看 pod里进程们到底共享什么namespace
## 查看 pause进程的 namespace信息
# ll /proc/19057/ns
总用量 0
lrwxrwxrwx 1 root root 0 6月 16 14:59 ipc -> ipc:[4026532659] ## same ；ipc namespace
lrwxrwxrwx 1 root root 0 6月 17 10:28 mnt -> mnt:[4026532657]
lrwxrwxrwx 1 root root 0 6月 16 14:59 net -> net:[4026532662] ## same ；net namespace
lrwxrwxrwx 1 root root 0 6月 17 10:28 pid -> pid:[4026532660]
lrwxrwxrwx 1 root root 0 6月 17 10:28 user -> user:[4026531837] ## same ；user namespace
lrwxrwxrwx 1 root root 0 6月 17 10:28 uts -> uts:[4026532658]
## 查看 redis进程的 namespace信息
# ll /proc/19356/ns
总用量 0
lrwxrwxrwx 1 100 101 0 6月 16 15:13 ipc -> ipc:[4026532659] ## same
lrwxrwxrwx 1 100 101 0 6月 16 15:13 mnt -> mnt:[4026532654]
lrwxrwxrwx 1 100 101 0 6月 16 15:13 net -> net:[4026532662] ## same
lrwxrwxrwx 1 100 101 0 6月 16 15:13 pid -> pid:[4026532656]
lrwxrwxrwx 1 100 101 0 6月 16 15:13 user -> user:[4026531837] ## same
lrwxrwxrwx 1 100 101 0 6月 16 15:13 uts -> uts:[4026532655]
## 查看 nginx进程的 namespace信息
# ll /proc/19431/ns
总用量 0
lrwxrwxrwx 1 root root 0 6月 16 15:13 ipc -> ipc:[4026532659] ## same
lrwxrwxrwx 1 root root 0 6月 16 15:13 mnt -> mnt:[4026532849]
lrwxrwxrwx 1 root root 0 6月 16 15:13 net -> net:[4026532662] ## same
lrwxrwxrwx 1 root root 0 6月 16 15:13 pid -> pid:[4026532851]
lrwxrwxrwx 1 root root 0 6月 16 15:13 user -> user:[4026531837] ## same
lrwxrwxrwx 1 root root 0 6月 16 15:13 uts -> uts:[4026532850]
四、总结pod和容器的关系
pod是k8s抽象出来的资源类型，是k8s调度的最小单位。这是事实，但是为什么会有pod呢？直接用容器不好吗？
-- 不好！首先容器里只启动一个进程这基本是共识了，那联系紧密的几个进程怎么办，pod维持多个容器紧密联系，他们共享ipc，net和user namespace，他们属于同一组 cgroup，作为一个整体来参与调度；
-- 二、容器技术不只是containerd 这一种引擎，还有 rkt，cri-o等，k8s需要pod这一层更高级的抽象。