Temporarily enable Debugging in the Linux Agent

There is no switch to permanently enable the debug mode in the check_mk_agent for Linux.
The problem with that is, that the output has to be written to a file. Sending it to the CMK Server would lead to a CRIT "Check_MK" service.

Enabling the Debug Mode

To write the debug output to a file on one monitored host, you have to do the following:

1. Create a backup of your check_mk_agent script

cp /usr/bin/check_mk_agent /usr/bin/check_mk_agent.bak

2. Edit the script and add the following lines in the main_setup() routine, after the line set_up_process_commandline_arguments "$@":

     #############################################
    # Permamently enable debug mode

    # log rotation
    logfile=/var/log/agent.out
    max_logs=10  # Adjust the maximum number of stored log files to your needs.
    i=$max_logs

    while [ $i -gt 1 ]; do
        ((j=i-1))
        if [ -f $logfile.$j ]; then
            mv $logfile.$j $logfile.$i
        fi
        i=$j
    done

    if [ -f $logfile ]; then
        mv $logfile $logfile.1
    fi

    # write stderr to log
    set -xv
    exec 2>$logfile

    # Enabling debug END
    ############################################# 

Disabling the Debug Mode

To disable the debug mode, simply copy your original script:

cp /usr/bin/check_mk_agent.bak /usr/bin/check_mk_agent

Limitations

When you're using the Automatic Agent Updater, it might happen that your modified script will be overwritten.