Daemon::Control - Create init scripts in Perl
Daemon::Control provides a library for creating init scripts in perl. Your perl script just needs to set the accessors for what and how you want something to run and the library takes care of the rest.
You can launch programs through the shell (/usr/sbin/my_program) or launch Perl code itself into a daemon mode. Single and double fork methods are supported and in double-fork mode all the things you would expect like reopening STDOUT/STDERR, switching UID/GID are supported.
Write a program that describes the daemon:
#!/usr/bin/perl use warnings; use strict; use Daemon::Control; Daemon::Control->new({ name => "My Daemon", lsb_start => '$syslog $remote_fs', lsb_stop => '$syslog', lsb_sdesc => 'My Daemon Short', lsb_desc => 'My Daemon controls the My Daemon daemon.', path => '/home/symkat/etc/init.d/program', program => '/home/symkat/bin/program', program_args => [ '-a', 'orange', '--verbose' ], pid_file => '/tmp/mydaemon.pid', stderr_file => '/tmp/mydaemon.out', stdout_file => '/tmp/mydaemon.out', fork => 2, })->run;
You can then call the program:
/home/symkat/etc/init.d/program start
You can also make an LSB compatable init script:
/home/symkat/etc/init.d/program get_init_file > /etc/init.d/program
The constuctor takes the following arguments.
The name of the program the daemon is controlling. This will be used in status messages "name [Started]" and the name for the LSB init script that is generated.
This can be a coderef or the path to a shell program that is to be run.
$daemon->program( sub { ... } );
$daemon->program( "/usr/sbin/http" );
This is an array ref of the arguments for the program. In the context of a coderef being executed this will be given to the coderef as @_, the Daemon::Control instance that called the coderef will be passed as the first arguments. Your arguments start at $_[1].
In the context of a shell program, it will be given as arguments to be executed.
$daemon->program_args( [ 'foo', 'bar' ] );
$daemon->program_args( [ '--switch', 'argument' ] );
When set, the username supplied to this accessor will be used to set the UID attribute. When this is used, uid will be changed from its inital settings if you set it (which you shouldn't, since you're using usernames instead of UIDs). See "uid" for setting numerical user ids.
uid
$daemon->user('www-data');
When set, the groupname supplied to this accessor will be used to set the GID attribute. When this is used, gid will be changed from its inital settings if you set it (which you shouldn't, since you're using groupnames instead of GIDs). See "gid" for setting numerical group ids.
gid
$daemon->group('www-data');
If provided, the UID that the program will drop to when forked. This is ONLY supported in double-fork mode and will only work if you are running as root. Accepts numeric UID. For usernames please see "user".
$daemon->uid( 1001 );
If provided, the GID that the program will drop to when forked. This is ONLY supported in double-fork mode and will only work if you are running as root. Accepts numeric GID, for groupnames please see "group".
$daemon->gid( 1001 );
If provided, chdir to this directory before execution.
The path of the script you are using Daemon::Control in. This will be used in the LSB file genration to point it to the location of the script. If this is not provided $0 will be used, which is likely to work only if you use the full path to execute it when asking for the init script.
The name of the init config file to load. When provided your init script will source this file to include the environment variables. This is useful for setting a PERL5LIB and such things.
$daemon->init_config( "/etc/default/my_program" );
By default this is set true. STDOUT will be redirected to stdout_file, STDERR will be redirected to stderr_file. Setting this to 0 will disable redriecting before a double fork. This is useful when you are using a code ref and would like to leave the file handles alone until you're in control.
Call ->redirect_filehandles on the Daemon::Control instance your coderef is passed to redirect the filehandles.
If provided stdout will be redirected to the given file. This is only supported in double fork more.
$daemon->stdout_file( "/tmp/mydaemon.stdout" );
If provided stderr will be redirected to the given file. This is only supported in double fork more.
$daemon->stderr_file( "/tmp/mydaemon.stderr" );
The location of the PID file to use. Warning: if using single-fork mode, it is recommended to set this to the file which the daemon launching in single-fork mode will put it's PID. Failure to follow this will most likely result in status, stop, and restart not working.
$daemon->pid_file( "/tmp/mydaemon.pid" );
The mode to use for fork. By default a double-fork will be used.
In double-fork, uid, gid, std*_file, and a number of other things are supported. A traditional double-fork is used and setsid is called.
In single-fork none of the above are called, and it is the responsiblity of whatever you're forking to reopen files, associate with the init process and do all that fun stuff. This mode is recommended when the program you want to control has it's own daemonizing code. It is importand to note that the PID file should be set to whatever PID file is used by the daemon.
$daemon->fork( 1 );
$daemon->fork( 2 ); # Default
This provides an extra check to see if the program is running. Normally we only check that the PID listed in the PID file is running. When given a regular expression, we will also match the name of the program as shown in ps.
$daemon->scan_name( qr|mydaemon| );
The value of this string is used for the 'Required-Start' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.
$daemon->lsb_start( '$remote_fs $syslog' );
The value of this string is used for the 'Required-Stop' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.
$daemon->lsb_stop( '$remote_fs $syslog' );
The value of this string is used for the 'Short-Description' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.
$daemon->lsb_sdesc( 'Mah program...' );
The value of this string is used for the 'Description' value of the generated LSB init script. See http://wiki.debian.org/LSBInitScripts for more information.
$daemon->lsb_desc( 'My program controls a thing that does a thing.' );
This will make your program act as an init file, accepting input from the command line. Run will exit either 1 or 0, following LSB files on exiting. As such no code should be used after ->run is called. Any code in your file should be before this.
Is called when start is given as an argument. Starts the forking, and exits.
/usr/bin/my_program_launcher.pl start
Is called when stop is given as an argument. Stops the running program if it can.
/usr/bin/my_program_launcher.pl stop
Is called when restart is given as an argument. Calls do_stop and do_start.
/usr/bin/my_program_launcher.pl restart
Is called when status is given as an argument. Displays the status of the program, basic on the PID file.
/usr/bin/my_program_launcher.pl status
Is called when get_init_file is given as an argument. Dumps an LSB compatable init file, for use in /etc/init.d/
/usr/bin/my_program_launcher.pl get_init_file
This is used to display status to the user. It accepts a message, and a color. It will default to green text, if no color is explictly given. Only supports red and green.
$daemon->pretty_print( "My Status", "red" );
This will write the PID to the file in pid_file.
This will read the PID from the file in pid_file and set it in pid.
An accessor for the PID. Set by read_pid, or when the program is started.
A function to dump the LSB compatable init script. Used by do_get_init_file.
SymKat <symkat@symkat.com> ( Blog: http://symkat.com/ )
Matt S. Trout (mst) <mst@shadowcat.co.uk>
Mike Doherty (doherty) <doherty@cpan.org>
Copyright (c) 2012 the Daemon::Control "AUTHOR" and "CONTRIBUTORS" as listed above.
This library is free software and may be distributed under the same terms as perl itself.
The most current version of Daemon::Control can be found at https://github.com/symkat/Daemon-Control
To install Daemon::Control, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Daemon::Control
CPAN shell
perl -MCPAN -e shell install Daemon::Control
For more information on module installation, please visit the detailed CPAN module installation guide.