[Dave N]

A person where I work started up her late 2011 iMac (running 10.7) and it booted itself into the root command line. It was a black screen with white text. I did a command line restart and it booted normally into OS X. This computer has a standard install of 10.7 and has never been tinkered with by anyone (no power users). Was this a one time fluke, or something to be concerned about? Could this be a virus or anything else? Thanks.

[Thorzdad]

Perhaps they accidentally had the Shift key pressed and booted into Safe Mode?

[Dave N]

Thanks for the reply. I noticed the wireless keyboard battery is low, so maybe it could have been sending some strange signals??? Someone in my building said it could have been a kernel panic. I guess I should have read more of what was on the screen, or taken a picture.

[Spheric Harlot]

If you were able to reboot using the command line, it was not a kernel panic.

Holding the shift key at startup boots into Safe Mode, not single-user mode.

Single-user mode (a functional command-line prompt) is achieved by holding down "S" (or Cmd-S) at startup.

[Dave N]

OK, I just booted my 10.8 mini into single user mode and got exactly the same thing that was on the imac. So I'm assuming that this person may have inadvertently held down the command-s keys, or maybe the low battery in the keyboard caused it.

[Waragainstsleep]

I've seen this happen before. Nothing to worry about unless it persists.