How to Fix \'Command Not Found\' Error in Python Paramiko exec_command?

Unix Commands Failing with "Command Not Found" in Python Paramiko exec_command

When executing Unix commands using Python's Paramiko exec_command, it's possible to encounter an error such as " not found." This issue arises specifically when using the sesu command, while other commands like ls execute successfully.

Underlying Cause

The cause lies in the default behavior of SSHClient.exec_command, which doesn't run a "login" shell and doesn't allocate a pseudo terminal for the session. As a result, different startup scripts may run and specific environment variables might not be set.

Possible Solutions

To resolve this, several approaches can be taken:

1. Utilize a Full Command Path: Use the complete path to the sesu executable, ensuring the command is independent of the environment.
2. Adjust Startup Scripts: Modify startup scripts to consistently set PATH for both interactive and non-interactive sessions.
3. Explicitly Invoke Login Shell: Run the script using --login with compatible shells, such as:

bash --login -c "sesu test"

4. Modify Command Environment: Alter the command itself to include specific environment settings:

PATH="$PATH;/path/to/sesu" && sesu test

5. Force Pseudo Terminal Use: (Not recommended) Enable pseudo terminal allocation by setting get_pty to True:

stdin,stdout,stderr = ssh.exec_command('sesu test', get_pty=True)

Additional Considerations

• Verify LD_LIBRARY_PATH and ensure it accurately locates shared objects.

• Refer to these resources for further insights:

  • [Environment Variable Differences When Using Paramiko](https://stackoverflow.com/questions/13781377/environment-variable-differences-when-using-paramiko)
  • [Certain Unix Commands Fail with "... Not Found" in JSch](https://stackoverflow.com/questions/44950115/certain-unix-commands-fail-with-not-found-when-executed-through-java-using-jsch)

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