Using the launch daemon

You might have already noticed that some jobs are automatically launched when the Haiku system starts.

In this article let's review how it's done, and in which case it can be useful to define a launch daemon for your applications packages or for your personal usage.

Before moving forward, the launch daemon is making a difference between a service and a job :

• a service is re-started automatically by the launch_daemon as soon as it's quit (or has crashed)
• a job is only started once (like when the system starts)

Now let's review that in details.

Existing system launch daemon

The existing system launch daemon is available in "/system/data/launch".

Open a Terminal and type :

cd /system/data/launch
lpe system

You should see the below services or jobs :

For instance, let's check the "net_server" service :

launch_roster list | grep net_server

You can retrieve the information relative to this service :

launch_roster info x-vnd.haiku-net_server

According to the help option, you can start/stop/restart a service or a job :

In case of a service, the stop command seems to not be effective :

In case of a job, the stop command is effective, however for the job below, it has been restarted by the system :

Existing user launch daemon

Now let's check the interesting part : the user launch daemon :)

The user launch daemon is available in "/system/data/user_launch".

To review the existing setup, open a Terminal and type :

/system/data/user_launch
lpe user &

Let's review - for instance - the user launch for LaunchBox :

    job x-vnd.Haiku-LaunchBox {
        launch /system/apps/LaunchBox
        if setting ~/config/settings/LaunchBox/main_settings autostart
        on initial_volumes_mounted
        legacy
        no_safemode
    }

This setup indicates that "x-vnd.Haiku-LaunchBox" :

• is a job
• is launching the application "/system/apps/LaunchBox"
• will start only when the settings "main_settings" is true (ie it decodes the flattened BMessage ~/config/settings/LaunchBox/main_settings and checks if there’s a field named “autostart” and sees if it’s true or false)
• is not started when safemode is used from the bootloader

If you go further in the "user" file, you should see the "UserBootScript" below :

The "~/config/settings/boot/UserBootscript" is really interesting in case you need to start some specific commands during the boot of the system.

We will review that at the end of this article.

Last point, as you can see at the end of this "user" file, there's a run section where:

• the "first_boot" target is used the first time the system is booted
• the "desktop" target is used if not

Do you know that with launch_roster command, you can list the existing targets ?

launch_roster list-targets

Let's start the installer target then to check !

launch_roster start installer

It's working as expected :)

Specify a new user launch daemon

Now suppose you would like to create a new launch daemon for a specific usage.

For that you need to create the directory "user_launch" in "/system/non-packaged/data/" :

mkdir -p /system/non-packaged/data/user_launch

A good example is the PostgreSQL package which is not including a launch daemon once installed.

First install PostgreSQL server as explained in the Install PostgreSQL article.

Let's fix the auto-start of the server by adding a new user launch daemon.

In a terminal type :

lpe /system/non-packaged/data/user_launch/postgresql

Do a copy/paste of the below :

job x-vnd.postgresql {
  launch /bin/pg_ctl -D /boot/home/postgresql -l /boot/home/postgresql/postgresql.log start
  no_safemode
  legacy
  on initial_volumes_mounted
}

Save the file and quit.

Restart the sytem.

Open a Terminal, and verify the server is ready, and that you can connect to the server :

pg_isready
psql -h localhost -U postgres -W

Great !

You don't need anymore to start the server manually each time your system is starting.

UserBootScript as an alternative

If you remember, there's also the "UserBootScript" which is called during the system start process.

In case you don't want to bother with user launch daemon, the alternative is to modify this file.

First remove the "/system/non-packaged/data/user_launch/postgresql" created before.

Then edit this boot script file :

lpe ~/config/settings/boot/UserBootscript &

And paste the below line, to start the server when the system starts :

pg_ctl -D /boot/home/postgresql -l /boot/home/postgresql/postgresql.log start

Reboot your system and checks the results.

The "pg_isready" should indicate the server is ready as well !

I hope you have found this article interesting.

You can check for the existing documentation on the official website on the "Introduction to the Launch Daemon" page.