kubectl in pod works unexpectedly

Question

kubectl is installed in the pod. When kubectl is used to execute commands in another pod, some commands works as expected, and the others behave abnormally, such as echo.

• execute on host
• excecute in pod The host and pod have the same version of kubectl，is it related to some concept of tty? or something else? thx for any device.

I've tried to add privilege, tty, stdin to my kubectl pod, but not working. Yaml part as below:

containers:
  - name: bridge
    image: registry:5000/bridge:v1
    imagePullPolicy: IfNotPresent
    securityContext:
      privileged: true
    stdin: true
    tty: true
      

Answer 1

It depends on the container environment and limitations based on permissions or if the pod has the required software to run the commands.

As it appears echo is not present in the image which is deployed on pod. Though echo command is part of standard libraries and comes by default you can try installing it again.like in ubuntu use below

sudo apt-get update
sudo apt-get install coreutils

Answer 2

It was finally found to be related to my kubectl command in pod. Which is override by the following script. When I changed to the original kubectl command, everything works fine.

root@bridge-66d98bd46d-zk65m:/data/ww# cat /usr/bin/kubectl
#!/bin/bash
/opt/kubectl1 -ndefault $@
root@bridge-66d98bd46d-zk65m:/data/ww# /opt/kubectl1 -ndefault exec vnc-test -- bash -c 'which echo '
/usr/bin/echo
root@bridge-66d98bd46d-zk65m:/data/ww#