Remove _postgres user safely and completely from Mac /etc/passwd

Question

I'm am attempting to reinstall PostgreSQL as I am unable to log into it at all. I realise I had installed it a long time ago using both the installer from the postgres website and brew install postgres. I have uninstalled both of these now:

• uninstalled using brew uninstall --force postgresql to remove all versions installed via brew.
• uninstalled using sudo /Library/PostgreSQL/9.5/uninstall-postgresql.app/Contents/MacOS/installbuilder.sh
• manually removed /Library/PostgreSQL (rm -rf /Library/PostgreSQL)
• manually the PostgreSQL user (via the Mac Users & Groups).

However I have a _postgres user left in /etc/passwd:

$ grep post /etc/passwd
_postgres:*:216:216:PostgreSQL Server:/var/empty:/usr/bin/false

There are no userdel or usermod commands available on Mac (10.11 El Capitan) and the alternative seems excessively complex (but perhaps necessarily so?)

Solution

Use the command brew remove postgresql. Or investigate the uninstall scripts manually.

Edit: Have you tried this?

• Quit Postgres.app & drag it to the Trash

• Delete the data directory (default location: ~/Library/Application Support/Postgres)

• Delete preferences for Postgres.app by executing the following command: defaults delete com.postgresapp.Postgres2

• Remove the $PATH config for the command line tools (optional): sudo rm /etc/paths.d/postgresapp

Edit 2: To delete a user from the command line, boot into single user mode. Hold Command-s at startup. Check the filesystem: /sbin/fsck -fy If no remaining errors, mount the filesystem: /sbin/mount -uw / Start up directory services: launchctl load /System/Library/LaunchDaemons/com.apple.DirectoryServices.plist Note that single user mode said to use com.apple.DirectoryServicesLocal.plist, but that didn't work -- this did. Find what groups the user belongs to: dscl . -list /groups GroupMembership | grep username -- repeat for each group except for the user's own group. Remove the group corresponding to the username: dscl . delete /groups/username (this may not be necessary -- you may get an error that the group doesn't exist; you can ignore it and go on). Remove the user account: dscl . delete /users/username At this point, you may wish to remove or archive the user folder in /Users. You may wish to remove the .AppleSetupDone file in /var/db to cause the Setup Assistant to run when next booted. Type reboot to reboot the system or shutdown -h now to shut down the system.

Comments

[AJP]

thanks for the help. I have edited answer to make it clear I have already run this command

[user2497]

Oh - well, perhaps then reading the install/uninstall scripts will not be helpful.

[user2497]

I once messed around in the guts of OSX, assuming a normal passwd/group configuration. Even then it was a filthy experience. Jobs certainly made FreeBSD weirder.

[AJP]

Wow... that is intimidating. Thank you very much for your answer. Playing whack-a-mole with postgres has at some point resulted in success. When I reinstall with brew and ran createdb `whoami` I can now login to a psql shell successfully :) Thank you very much for the detailed answer. I'm going to mark this as correct though I haven't summoned the courage to try it!

[user2497]

It is prudent to perform a backup. I am not sure why they got rid of the classical passwd/group system, but it is certainly possible regardless of this obfuscation. When I went cavediving in OSX, I was also removing a user account that wouldn't be removed with conventional weapons, but that was long ago.

[user2497]

IIRC, on a multivolume setup, if you have your Users folder on another disk, you must invoke mount -uwa