In this official document, it can run command in a yaml config file:
apiVersion: v1
kind: Pod
metadata:
name: hello-world
spec: # specification of the pod’s contents
restartPolicy: Never
containers:
- name: hello
image: "ubuntu:14.04"
env:
- name: MESSAGE
value: "hello world"
command: ["/bin/sh","-c"]
args: ["/bin/echo \"${MESSAGE}\""]If I want to run more than one command, how to do?
Just to bring another possible option, secrets can be used as they are presented to the pod as volumes:
Secret example:
apiVersion: v1
kind: Secret
metadata:
name: secret-script
type: Opaque
data:
script_text: <<your script in b64>>Yaml extract:
....
containers:
- name: container-name
image: image-name
command: ["/bin/bash", "/your_script.sh"]
volumeMounts:
- name: vsecret-script
mountPath: /your_script.sh
subPath: script_text
....
volumes:
- name: vsecret-script
secret:
secretName: secret-scriptI know many will argue this is not what secrets must be used for, but it is an option.
Here is how you can pass, multiple commands & arguments in one YAML file with kubernetes:
# Write your commands here
command: ["/bin/sh", "-c"]
# Write your multiple arguments in args
args: ["/usr/local/bin/php /var/www/test.php & /usr/local/bin/php /var/www/vendor/api.php"]Full containers block from yaml file:
containers:
- name: widc-cron # container name
image: widc-cron # custom docker image
imagePullPolicy: IfNotPresent # advisable to keep
# write your command here
command: ["/bin/sh", "-c"]
# You can declare multiple arguments here, like this example
args: ["/usr/local/bin/php /var/www/tools/test.php & /usr/local/bin/php /var/www/vendor/api.php"]
volumeMounts: # to mount files from config-map generator
- mountPath: /var/www/session/constants.inc.php
subPath: constants.inc.php
name: widc-constantsIMHO the best option is to use YAML's native block scalars. Specifically in this case, the folded style block.
By invoking sh -c you can pass arguments to your container as commands, but if you want to elegantly separate them with newlines, you'd want to use the folded style block, so that YAML will know to convert newlines to whitespaces, effectively concatenating the commands.
A full working example:
apiVersion: v1
kind: Pod
metadata:
name: myapp
labels:
app: myapp
spec:
containers:
- name: busy
image: busybox:1.28
command: ["/bin/sh", "-c"]
args:
- >
command_1 &&
command_2 &&
...
command_n
command: ["/bin/sh","-c"]
args: ["command one; command two && command three"]Explanation: The command ["/bin/sh", "-c"] says "run a shell, and execute the following instructions". The args are then passed as commands to the shell. In shell scripting a semicolon separates commands, and && conditionally runs the following command if the first succeed. In the above example, it always runs command one followed by command two, and only runs command three if command two succeeded.
Alternative: In many cases, some of the commands you want to run are probably setting up the final command to run. In this case, building your own Dockerfile is the way to go. Look at the RUN directive in particular.
My preference is to multiline the args, this is simplest and easiest to read. Also, the script can be changed without affecting the image, just need to restart the pod. For example, for a mysql dump, the container spec could be something like this:
containers:
- name: mysqldump
image: mysql
command: ["/bin/sh", "-c"]
args:
- echo starting;
ls -la /backups;
mysqldump --host=... -r /backups/file.sql db_name;
ls -la /backups;
echo done;
volumeMounts:
- ...The reason this works is that yaml actually concatenates all the lines after the "-" into one, and sh runs one long string "echo starting; ls... ; echo done;".
If you're willing to use a Volume and a ConfigMap, you can mount ConfigMap data as a script, and then run that script:
---
apiVersion: v1
kind: ConfigMap
metadata:
name: my-configmap
data:
entrypoint.sh: |-
#!/bin/bash
echo "Do this"
echo "Do that"
---
apiVersion: v1
kind: Pod
metadata:
name: my-pod
spec:
containers:
- name: my-container
image: "ubuntu:14.04"
command:
- /bin/entrypoint.sh
volumeMounts:
- name: configmap-volume
mountPath: /bin/entrypoint.sh
readOnly: true
subPath: entrypoint.sh
volumes:
- name: configmap-volume
configMap:
defaultMode: 0700
name: my-configmapThis cleans up your pod spec a little and allows for more complex scripting.
$ kubectl logs my-pod
Do this
Do thatIf you want to avoid concatenating all commands into a single command with ; or && you can also get true multi-line scripts using an heredoc:
command:
- sh
- "-c"
- |
/bin/bash <<'EOF'
# Normal script content possible here
echo "Hello world"
ls -l
exit 123
EOF
This is handy for running existing bash scripts, but has the downside of requiring both an inner and an outer shell instance for setting up the heredoc.