Blog | Creating a service account on OS X (Yosemite)

17

Mar
2015
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Creating a service account on OS X (Yosemite)

Creating service users on OS X is not as straight forward as doing so on Linux system.  For starters, the useradd command is not available.

So in order to perform the same action on OS X, open a terminal window and run the following commands. For this example, I will create a group and user in order to run MongoDB.

[korey@localhost ~]$ sudo dscl . -list /Users UniqueID
_amavisd                83
_appleevents            55
_appowner               87
_appserver              79
_ard                    67
_assetcache             235
_astris                 245
_atsserver              97
_avbdeviced             229
_calendar               93
_ces                    32
_clamav                 82
_coreaudiod             202
_coremediaiod           236
_cvmsroot               212
....

The above command lists all the current users along with their UID. This is necessary so that we can pick an unused ID below 500 (UIDs above 500 are for normal users). You can run the same command with /Groups instead of /Users to get a list of groups.

First, lets create a group for the users with the same name:

[korey@localhost ~]$ sudo dscl . -create /Groups/_mongo gid 300
[korey@localhost ~]$ sudo dscl . -create /Groups/_mongo RealName "Mongo DB Server Group"
[korey@localhost ~]$ sudo dscl . -create /Groups/_mongo passwd "*"

As you can see the group ID is set to 300, and the password is set to “*”. This is a special password not to allow logins as that group of user. I am not certain if this is necessary, but looking at other similar groups on OS X, it seems to be the right way to do this.

Now, lets create the user and make sure that it will not show up as a user on the login screen:

[korey@localhost ~]$ sudo dscl . -create /Users/_mongo
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo uid 300
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo gid 300
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo NFSHomeDirectory /var/empty
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo UserShell /usr/bin/false
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo RealName "Mongo DB Server"
[korey@localhost ~]$ sudo dscl . -create /Users/_mongo passwd "*"

At this point, the service account is created, and its primary group set to the one we just created. Setting the shell and home folders are necessary to make sure that the account does not show up on the login screen and to ensure that even if someone does login as that user, they will not have access to anything. Once again, the account password here is set to “*” in order to not allow logins.

If you look at /etc/passwd on your OS X machine, you’ll notice that most service accounts are listed in there, but the above account is not. I am not sure if this will be problematic over the long term, but for all intents and purposes, the service account works as expected.

Naturally, I searched a good while before I came up with the above command set and here are some links that helped me:


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