While I didn't get excessively creative in naming the accounts, one is my Gmail and the other is my work's Google account showing off multiple user mode in an AOKP ROM.One of the neat things that Android 4.2.x brought about was support for multiple users on a device. Unfortunately, it appears that multiple user support has been confined primarily to the tablet world, even though support is built into most Android 4.2.2 AOSP code bases.

Update 11/19/13: how to make it stick added

My guess on the lack of support for multiple users is that there are simply fewer reasons to want it on a phone than there are on a tablet. But if you’re dealing with children wanting your phone to entertain themselves, or a device that’s been relegated to being a media server, you’ll discover soon enough how it would be a nice feature to have available.

Since multiple user mode and multiple profile support came out at roughly the same time, here’s a quick rundown on these so there’s no confusion:

Multiple Profile Support

This is the ability to set volume level, turn on and off radios, and adjust screen brightness based on the time of day, your location, the power situation, or just your preference.

An example of this would be turning off data, setting the brightness to 30%, and turning off system sounds and notifications after 10:oo p.m. every night, and then setting it back to normal at 6:00 a.m.

Multiple User Mode

Multiple User Mode is the ability to give the phone to another person, let them log in with their own account information, and any changes they make are done under their account. They give the phone back to you, and you’ll have none of their clutter, photos, emails, or apps on your account.

This enables you to give your phone to a relative to play with at a picnic and not get it back with 10,000 pay apps downloaded via Google Play, and all your email and icons deleted.

Preparations before proceeding

Since your ROM may not properly support multiple users, and all your data might be lost, make a nandroid backup of your phone before proceeding.

You’ll either need a functioning ADB client, or a terminal emulation application installed.

Onward

In a terminal window or ADB, you’ll need to obtain SuperUser/root access. This is generally done by typing in su. After obtaining SuperUser access, type in:

  • pm get-max-users

This should return the numeric result of “1,” which is the maximum number that the current OS is set up accept. If it returns an error, then your ROM is most likely unable to handle multiple users.

Next, you’ll need to change that number to something higher. In the following, I chose to set it to eight users because I felt like it.

Now type in:

  • setprop fw.max_users 8
  • pm create-user usernameyouwanthere

You may notice the shell reboot, and if you’re on a ROM build that supports multiple users properly, you’ll either get a login request, or a users section will appear under device in system settings. Depending on your ROM, you might even see an option in the developer’s menu to enable user selection in the power menu.

Keep in mind that this may not work completely or be supported by your ROM, but in some instances it’s quite useful. The worst that should happen is that you have to restore a nandroid, or that the max_users changes back to single-user after a reboot.

How to make it stick

Inspired by a comment from konnor below, this is how I got the multiple user mode to stick:

  • adb shell (if you’re not already, you can use terminal emulator if you want)
  • su
  • mount -o rw,remount /system
  • echo fw.max_users=4 >> build.prop
  • exit
  • exit
  • adb reboot (or reboot the device however you want)

From now on out the max_users will always be there when you boot.

After a reboot, swiping down and pressing my face brings me to the lock screen where all users are displayed. Your results may vary so make sure to have a nandroid backup.