Question

In debian lenny, when running /etc/init.d/tomcat5.5 start, it runs jsvc and expects it to daemonize itself.

From a simple bash shell, this works fine.

However, from a script, this gets completely stuck:

For example, the following works like a charm:

#!/usr/bin/perl
my $cmd = '/etc/init.d/tomcat5.5  start';
system($cmd);

However, the following gets stuck as jsvc does not daemonize:

#!/usr/bin/perl
my $cmd = '/etc/init.d/tomcat5.5  start';
`$cmd`;

It also gets stuck when running it using backticks in bash:

#!/bin/bash
CMD='/etc/init.d/tomcat5.5  start'
`$CMD`

Is this a bug in jsvc? Any idea why this works in a shell or using system() , but not using backticks? I am actually getting defunct/zombie processes because of this issue.

Answer 1

Just a hunch — for a job to become a daemon it needs to close any file descriptors that were opened in its parent process. Perhaps this is easier to do with system than with backticks/readpipe, though I can’t come up with any good reasons why that would be so. What if you used the backticks like:

`$CMD < /dev/null > /dev/null 2>&1`