Force launchd to re-read environment variables

launchd

Is there any way, short of rebooting, to force launchd to re-read environment variables newly defined in /etc/launchd.conf?

Can it be done with launchctl(1)?

Best Answer

There is no way to do this, "launchd" is the master process, the equivalent of "init" in other unix systems, the only way in any other daemon would be to perform some sort of kill -HUP to reload config files etc, but this operation is not permitted on launchd. If you look it up in the process table it is the number 1 process, every other process that is currently running is in some way a child of it, so a reboot is the only way to achieve this. You may have further luck in setting those environment variables in another area that is more inclined to allow restarts.

    Dans-iMac:etc stuffe$ ps -ef | grep launchd | grep -v grep
    0     1     0   0  9:40am ??         0:09.47 /sbin/launchd
   65    18     1   0  9:40am ??         1:53.64 /usr/sbin/mDNSResponder -launchd
  213    73     1   0  9:41am ??         0:02.55 /System/Library/PrivateFrameworks/MobileDevice.framework/Versions/A/Resources/usbmuxd -launchd
    0    85     1   0  9:41am ??         0:00.08 /System/Library/CoreServices/ODSAgent.app/Contents/MacOS/ODSAgent -launchd
   89   230     1   0  9:41am ??         0:00.01 /sbin/launchd
  501   238     1   0  9:41am ??         0:00.23 /sbin/launchd
  501   933   238   0 10:53am ??         0:00.01 /System/Library/CoreServices/AirPort Base Station Agent.app/Contents/MacOS/AirPort Base Station Agent -launchd -allowquit

EDIT:

Of course, missing the obvious solution that you can add the relevant variables into the config file, and then just run the commands manually in order to escape the need for a reboot, nothing that only newly start programs will take account of any changes. I found this page which explains it in more detail:

Environment variables set in launchd will be available to all programs on the system. However since $HOME/.launchd.conf is not supported, this approach is used for global environment variables only.

The /etc/launchd.conf file contains a list of commands to be run by launchctl during startup. However environment variables set in /etc/launchd.conf cannot have spaces and cannot reference other environment variables; launchctl when run in Terminal does not suffer these limitations. Do note that /etc/launchd.conf does not exist by default, so we will need to create it.

A reboot is necessary to load the contents of /etc/launchd.conf. However if you were to run the corresponding launchctlcommands in Terminal, you can alleviate the need for the reboot. Just remember that if you only do the launchctl commands, and do not put the entries in /etc/launchd.conf, it will not persist after reboot.

If you want to have a system wide environment variable that uses spaces or be dependent upon another environment variable, you can put the launchctl commands into one of the files Terminal reads. You will have to quit and relaunch Terminal to access the newly set variables.

Related Solutions

Launchd: ask user before performing tasks

Make launchd call this AppleScript. It displays a dialog with a timeout and calls a shell script if the user selected "Ok".

set timeoutInSeconds to 60
set abortOnTimeout to true

tell application (path to frontmost application as text)
    try
        set dialogResult to display dialog "Do you want to execute?" default button 2 giving up after timeoutInSeconds
        on error number -128
            return
    end try
end tell

if gave up of dialogResult and abortOnTimeout then
    return
end if

do shell script "/path/to/yourscript.sh"

Defining environment variables with launchd/launchctl

For the sake of clarity, I will refer to this solution as the static solution, the second solution as the dynamic solution, and finally this one as the launch agent solution. I am going to compare the static and dynamic solution with the launch agent one, respectively.

The static solution involves the editing of /etc/launchd.conf. This has the advantage, as with the launch agent solution, that the variables are set right at the login. Disadvantages are that

the variables are defined for all users. The launch agent solution lets each user decide for himself. If one wants to define variables for all users with the launch agent solution, the shell script can be amended with a loop (and another file),
the definition of the variables in /etc/launchd.conf does not allow for things like variable substitution and such stuff (at least that is my guess, maybe it is feasible),
obviously, you need access to /etc/launchd.conf to pull the static solution off, with the other one you can put all files at accessible places, e.g. the launch agent in ~/Library/LaunchAgents/,
the variables are not available immediately after editing the file, as with the launch agent solution (but see below).

The dynamic solution is similar to the launch agent solution. Its disadvantage is that the variables are not available right after login, you first need to (re-)define them. To combine the dynamic solution with the other, imagine you wanted to set the variable FOO to the content of the variable BAR. You would fire up a shell, say the bash, and type

launchctl setenv FOO "$BAR"
echo 'setenv FOO $BAR' >> ~/.conf.launchd

Then FOO would be available in all applications started after this definition, and would also be defined right after the next login.

Best Answer

Related Solutions

Launchd: ask user before performing tasks

Defining environment variables with launchd/launchctl

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