Debugging Kubernetes nodes with crictl
Kubernetes v1.11
stable
- The version name is vX where X is an integer.
- Stable versions of features will appear in released software for many subsequent versions.
crictl
is a command-line interface for CRI-compatible container runtimes.
You can use it to inspect and debug container runtimes and applications on a
Kubernetes node. crictl
and its source are hosted in the
cri-tools repository.
Before you begin
crictl
requires a Linux operating system with a CRI runtime.
Installing crictl
You can download a compressed archive crictl
from the cri-tools release
page, for several
different architectures. Download the version that corresponds to your version
of Kubernetes. Extract it and move it to a location on your system path, such as
/usr/local/bin/
.
General usage
The crictl
command has several subcommands and runtime flags. Use
crictl help
or crictl <subcommand> help
for more details.
crictl
connects to unix:///var/run/dockershim.sock
by default. For other
runtimes, you can set the endpoint in multiple different ways:
- By setting flags
--runtime-endpoint
and--image-endpoint
- By setting environment variables
CONTAINER_RUNTIME_ENDPOINT
andIMAGE_SERVICE_ENDPOINT
- By setting the endpoint in the config file
--config=/etc/crictl.yaml
You can also specify timeout values when connecting to the server and enable or
disable debugging, by specifying timeout
or debug
values in the configuration
file or using the --timeout
and --debug
command-line flags.
To view or edit the current configuration, view or edit the contents of /etc/crictl.yaml
.
cat /etc/crictl.yaml
runtime-endpoint: unix:///var/run/dockershim.sock
image-endpoint: unix:///var/run/dockershim.sock
timeout: 10
debug: true
Example crictl commands
The following examples show some crictl
commands and example output.
Warning: If you usecrictl
to create pod sandboxes or containers on a running Kubernetes cluster, the Kubelet will eventually delete them.crictl
is not a general purpose workflow tool, but a tool that is useful for debugging.
List pods
List all pods:
crictl pods
The output is similar to this:
POD ID CREATED STATE NAME NAMESPACE ATTEMPT
926f1b5a1d33a About a minute ago Ready sh-84d7dcf559-4r2gq default 0
4dccb216c4adb About a minute ago Ready nginx-65899c769f-wv2gp default 0
a86316e96fa89 17 hours ago Ready kube-proxy-gblk4 kube-system 0
919630b8f81f1 17 hours ago Ready nvidia-device-plugin-zgbbv kube-system 0
List pods by name:
crictl pods --name nginx-65899c769f-wv2gp
The output is similar to this:
POD ID CREATED STATE NAME NAMESPACE ATTEMPT
4dccb216c4adb 2 minutes ago Ready nginx-65899c769f-wv2gp default 0
List pods by label:
crictl pods --label run=nginx
The output is similar to this:
POD ID CREATED STATE NAME NAMESPACE ATTEMPT
4dccb216c4adb 2 minutes ago Ready nginx-65899c769f-wv2gp default 0
List images
List all images:
crictl images
The output is similar to this:
IMAGE TAG IMAGE ID SIZE
busybox latest 8c811b4aec35f 1.15MB
k8s-gcrio.azureedge.net/hyperkube-amd64 v1.10.3 e179bbfe5d238 665MB
k8s-gcrio.azureedge.net/pause-amd64 3.1 da86e6ba6ca19 742kB
nginx latest cd5239a0906a6 109MB
List images by repository:
crictl images nginx
The output is similar to this:
IMAGE TAG IMAGE ID SIZE
nginx latest cd5239a0906a6 109MB
Only list image IDs:
crictl images -q
The output is similar to this:
sha256:8c811b4aec35f259572d0f79207bc0678df4c736eeec50bc9fec37ed936a472a
sha256:e179bbfe5d238de6069f3b03fccbecc3fb4f2019af741bfff1233c4d7b2970c5
sha256:da86e6ba6ca197bf6bc5e9d900febd906b133eaa4750e6bed647b0fbe50ed43e
sha256:cd5239a0906a6ccf0562354852fae04bc5b52d72a2aff9a871ddb6bd57553569
List containers
List all containers:
crictl ps -a
The output is similar to this:
CONTAINER ID IMAGE CREATED STATE NAME ATTEMPT
1f73f2d81bf98 busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47 7 minutes ago Running sh 1
9c5951df22c78 busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47 8 minutes ago Exited sh 0
87d3992f84f74 nginx@sha256:d0a8828cccb73397acb0073bf34f4d7d8aa315263f1e7806bf8c55d8ac139d5f 8 minutes ago Running nginx 0
1941fb4da154f k8s-gcrio.azureedge.net/hyperkube-amd64@sha256:00d814b1f7763f4ab5be80c58e98140dfc69df107f253d7fdd714b30a714260a 18 hours ago Running kube-proxy 0
List running containers:
crictl ps
The output is similar to this:
CONTAINER ID IMAGE CREATED STATE NAME ATTEMPT
1f73f2d81bf98 busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47 6 minutes ago Running sh 1
87d3992f84f74 nginx@sha256:d0a8828cccb73397acb0073bf34f4d7d8aa315263f1e7806bf8c55d8ac139d5f 7 minutes ago Running nginx 0
1941fb4da154f k8s-gcrio.azureedge.net/hyperkube-amd64@sha256:00d814b1f7763f4ab5be80c58e98140dfc69df107f253d7fdd714b30a714260a 17 hours ago Running kube-proxy 0
Execute a command in a running container
crictl exec -i -t 1f73f2d81bf98 ls
The output is similar to this:
bin dev etc home proc root sys tmp usr var
Get a container’s logs
Get all container logs:
crictl logs 87d3992f84f74
The output is similar to this:
10.240.0.96 - - [06/Jun/2018:02:45:49 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.47.0" "-"
10.240.0.96 - - [06/Jun/2018:02:45:50 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.47.0" "-"
10.240.0.96 - - [06/Jun/2018:02:45:51 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.47.0" "-"
Get only the latest N
lines of logs:
crictl logs --tail=1 87d3992f84f74
The output is similar to this:
10.240.0.96 - - [06/Jun/2018:02:45:51 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.47.0" "-"
Run a pod sandbox
Using crictl
to run a pod sandbox is useful for debugging container runtimes.
On a running Kubernetes cluster, the sandbox will eventually be stopped and
deleted by the Kubelet.
Create a JSON file like the following:
{ "metadata": { "name": "nginx-sandbox", "namespace": "default", "attempt": 1, "uid": "hdishd83djaidwnduwk28bcsb" }, "logDirectory": "/tmp", "linux": { } }
Use the
crictl runp
command to apply the JSON and run the sandbox.crictl runp pod-config.json
The ID of the sandbox is returned.
Create a container
Using crictl
to create a container is useful for debugging container runtimes.
On a running Kubernetes cluster, the sandbox will eventually be stopped and
deleted by the Kubelet.
Pull a busybox image
crictl pull busybox Image is up to date for busybox@sha256:141c253bc4c3fd0a201d32dc1f493bcf3fff003b6df416dea4f41046e0f37d47
Create configs for the pod and the container:
Pod config:
{ "metadata": { "name": "nginx-sandbox", "namespace": "default", "attempt": 1, "uid": "hdishd83djaidwnduwk28bcsb" }, "log_directory": "/tmp", "linux": { } }
Container config:
{ "metadata": { "name": "busybox" }, "image":{ "image": "busybox" }, "command": [ "top" ], "log_path":"busybox.log", "linux": { } }
Create the container, passing the ID of the previously-created pod, the container config file, and the pod config file. The ID of the container is returned.
crictl create f84dd361f8dc51518ed291fbadd6db537b0496536c1d2d6c05ff943ce8c9a54f container-config.json pod-config.json
List all containers and verify that the newly-created container has its state set to
Created
.crictl ps -a
The output is similar to this:
CONTAINER ID IMAGE CREATED STATE NAME ATTEMPT 3e025dd50a72d busybox 32 seconds ago Created busybox 0
Start a container
To start a container, pass its ID to crictl start
:
crictl start 3e025dd50a72d956c4f14881fbb5b1080c9275674e95fb67f965f6478a957d60
The output is similar to this:
3e025dd50a72d956c4f14881fbb5b1080c9275674e95fb67f965f6478a957d60
Check the container has its state set to Running
.
crictl ps
The output is similar to this:
CONTAINER ID IMAGE CREATED STATE NAME ATTEMPT
3e025dd50a72d busybox About a minute ago Running busybox 0
See kubernetes-incubator/cri-tools for more information.
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