ctr和crictl都是Kubernetes环境中管理容器的命令行工具。但它们的目的和使用方法有所不同。
crictl是基于Kubernetes的CRI: Container Runtime Interface接口规范来管理容器, ctr是containerd自带的容器管理工具, 本身和Kubernetes无关。
Kubernetes使用crictl来管理任意兼容CRI接口的容器运行时。
containerd相比于docker，增加了namespace的概念，每个image和container都在各自的namespace下可见。目前kubernetes使用k8s.io作为namespace名称。
所以在使用containerd的kubernetes环境中，要使用ctr命令查看时，如果简单执行如下命令，是没有容器输出的:
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| [root@k8s-worker0 ~]# ctr container list
CONTAINER IMAGE RUNTIME
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需要添加namespace参数，如:
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| [root@k8s-worker0 ~]# ctr -n k8s.io container list
0eada175936306b1d0e428a38770e505d113e82c783b86dd8b4bfa44a93f3782 registry.k8s.io/pause:3.9 io.containerd.runc.v2
222177e2ab84d450f7d2529757d4e7dcf5c7a2cefe046843774aa6b667f31ed4 registry.k8s.io/pause:3.9 io.containerd.runc.v2
2b98414edc9a525fb649f00c176ab8bfad460fe35708efe3eaf089c111eb1ee7 registry.k8s.io/pause:3.9 io.containerd.runc.v2
3c75a2b3d7956b7a4aa25770f7c569d1e5d817438e787782b3e9e00c80ea79c7 registry.k8s.io/pause:3.9 io.containerd.runc.v2
3e6f73eab4bc200c436842c7d95055224731839791957fb58b9c8baf867dee46 registry.k8s.io/pause:3.9 io.containerd.runc.v2
56dbc8de39cf32c9734aeb935b54d556b05ba7512d15cac2ddaa545e502d22da registry.k8s.io/pause:3.9 io.containerd.runc.v2
6ee605bc01510e40341c98149f90ed6693b6557b5cd5c8836c61d01f34b2d51a registry.k8s.io/kube-proxy:v1.29.0 io.containerd.runc.v2
7228c44c6b5ad68bb8bb6aecf1fec72f121edd2dadcefe37ab4dd9869e093b32 registry.k8s.io/pause:3.9 io.containerd.runc.v2
7f52db24f19507da4fdd232eea23fb87e5a1ae7763e255af0f04516a7c9bb008 registry.k8s.io/pause:3.9 io.containerd.runc.v2
8a360bbb308aafebde4371a84000aaa5ebf300f1a4d1169dbf14ad02d3e5658d registry.k8s.io/pause:3.9 io.containerd.runc.v2
a915e48150bb7d4488893261da59bed87e1a3e574e847fb966e5eeb360e2e3ed registry.k8s.io/pause:3.9 io.containerd.runc.v2
b68eb4ae7d918f20689eba8bb4d109c02d2b333a3ffda3b656f30d1bf461d19c registry.k8s.io/pause:3.9 io.containerd.runc.v2
b968b8f6ac6a93543ba13de31893daa1e6ddac296cacda4c8e836a2c8148d824 registry.k8s.io/pause:3.9 io.containerd.runc.v2
ba36dab2f3c65f2478d6a25252e7844260fdaa2af779c6f1381c02540185c29b registry.k8s.io/pause:3.9 io.containerd.runc.v2
d6d4332bbfb1e8b1f179947fd1301e9646c19473c00d885e798c111291667f6c registry.k8s.io/pause:3.9 io.containerd.runc.v2
e8ae98caf2f066a97197a7705159d57cc0224fa2d3ba904e814f76adb586ff2c registry.k8s.io/pause:3.9 io.containerd.runc.v2
f0c578821e55910df0b8b7c3889037004db222493d85ad9ace8527d45e973be8 registry.k8s.io/pause:3.9 io.containerd.runc.v2
f5a33aaccdb1c968bbfcbe9428d0ae5a70b59a8618724ed27e55f85d11bb8cb4 registry.k8s.io/pause:3.9 io.containerd.runc.v2
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如果需要容器关联的POD信息，需要使用crictl:
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| [root@cluster1 ~]# crictl ps
CONTAINER IMAGE CREATED STATE NAME ATTEMPT POD ID POD
0847e65e20b43 14d7d9ac51894 29 hours ago Running mariadb 0 4f2535726e06f mysql-mariadb-0
4bb865f74a8a7 11a5d8a9f31aa 31 hours ago Running lb-tcp-3129 0 5014c89cfe109 svclb-frontend-lb-06a5c6f4-r45ls
68d22a1d09ea1 11a5d8a9f31aa 31 hours ago Running lb-tcp-20001 0 5014c89cfe109 svclb-frontend-lb-06a5c6f4-r45ls
6c75bf330db4a 11a5d8a9f31aa 31 hours ago Running lb-tcp-7902 0 5014c89cfe109 svclb-frontend-lb-06a5c6f4-r45ls
ee41385abf1d7 11a5d8a9f31aa 31 hours ago Running lb-tcp-7901 0 5014c89cfe109 svclb-frontend-lb-06a5c6f4-r45ls
7360a6ee7b30a 11a5d8a9f31aa 31 hours ago Running lb-tcp-443 0 5014c89cfe109 svclb-frontend-lb-06a5c6f4-r45ls
f1dc52862daaf 3a0f7b0a13ef6 2 weeks ago Running registry 0 dcbea1d5918ca registry-795cf4cd5-6djg2
b4b864e0a38a2 c69fa2e9cbf5f 2 weeks ago Running coredns 0 af17c0e59afc2 coredns-56f6fc8fd7-fqd87
a210c70357684 48d9cfaaf3904 2 weeks ago Running metrics-server 0 db363ba6b01e3 metrics-server-5985cbc9d7-vvklc
4423e81878099 5d221316a3c61 2 weeks ago Running local-path-provisioner 0 b4c91a7452716 local-path-provisioner-846b9dcb6c-48nqw
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查询节点上所有的POD：
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| [root@cluster1 ~]# crictl pods
POD ID CREATED STATE NAME NAMESPACE ATTEMPT RUNTIME
5014c89cfe109 31 hours ago Ready svclb-frontend-lb-06a5c6f4-r45ls kube-system 0 (default)
af17c0e59afc2 2 weeks ago Ready coredns-56f6fc8fd7-fqd87 kube-system 0 (default)
db363ba6b01e3 2 weeks ago Ready metrics-server-5985cbc9d7-vvklc kube-system 0 (default)
b4c91a7452716 2 weeks ago Ready local-path-provisioner-846b9dcb6c-48nqw kube-system 0 (default)
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参考: