Cannot execute job that runs a shell script

I have the following pl/sql script that should execute the shell script script.sh. When I runt the code below In SQLDeveloper I get:

    Error report -
ORA-27370: job slave failed to launch a job of type EXECUTABLE
ORA-27300: OS system dependent operation:accessing login executable failed with status: 2
ORA-27301: OS failure message: No such file or directory
ORA-27302: failure occurred at: sjseccel 1
ORA-06512: at "SYS.DBMS_ISCHED", line 185
ORA-06512: at "SYS.DBMS_SCHEDULER", line 486
ORA-06512: at line 20
27370. 00000 -  "job slave failed to launch a job of type EXECUTABLE"
*Cause:    The scheduler ran into an error when the job slave tried to start
           a job of type EXECUTABLE. The rest of the error stack will provide
           more detailed information on what the exact problem was.
*Action:   Correct the problem specified in the error stack and reschedule
           the job.

The file exists and has the correct permissions on my system. Is something that I am doing wrong? Also, the provided credentials seem to be the correct ones.

An here is the code:

set serveroutput on;

BEGIN
    DBMS_SCHEDULER.create_credential(
        credential_name => 'user_cred',
        username        => 'user',
        password        => 'pass');  
END;   
/

begin
      DBMS_SCHEDULER.CREATE_JOB (
        job_name           => 'test_prog',
         job_type           => 'EXECUTABLE',
        job_action         => '/home/user/Desktop/foo/script.sh',
         enabled            => TRUE,
         credential_name => 'user_cred'
      );
    dbms_scheduler.run_job('test_prog');
end;
/