I run this command from my Ubuntu 14.04 computer:
adb shell sm set-force-adoptable true
and I get the following error:
/system/bin/sh: sm: not found
It seems to me that this is about my computer and not the Android device. How can I install sm?
It seems unlikely it is your Ubuntu computer because you are using an adb shell command.
You can run
adb shell as a separate command and verify that you enter the shell of the device without any issue. This confirms that you are now running commands on the device instead of your computer. If you can't shell into the device, then it would in fact be an issue with your computer.
Is it a Genymotion device or a standard Android emulator?