How to Resolve \'Command Not Found\' Error in Paramiko\'s exec_command for Unix Commands?

Unix Commands Failing with "Command Not Found" Error When Using Paramiko's exec_command

In scenarios where Unix commands like "sesu" fail with "command not found" errors when executed via Python's Paramiko exec_command, the root cause may lie in the default behavior of SSHClient.exec_command.

Understanding the Default Behavior

SSHClient.exec_command typically does not operate in "login" mode or allocate pseudo terminals for sessions. Consequently, it may bypass certain startup scripts that are invoked during interactive SSH sessions. This discrepancy can result in environment variables and script branching differing from regular interactive sessions.

Fixing the Issue

To address this problem, consider the following solutions:

1. Specify the Full Path to the Command: Instead of relying on PATH, use the full path to the command, e.g., "/bin/sesu test."
2. Modify Startup Scripts: Ensure that startup scripts set the PATH consistently for both interactive and non-interactive sessions.
3. Run the Command via Login Shell: Use the "--login" switch to explicitly execute the command via a login shell, e.g., "bash --login -c "sesu test"."
4. Modify the Command Environment: Alter the environment within the command itself, ensuring that essential variables are set correctly.
5. Force Pseudo Terminal Allocation (Not Recommended): Set the "get_pty" parameter to True to allocate a pseudo terminal for the exec channel. However, this method can have unintended consequences.

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