For the first single time I just had to log twice from the screensaver, and the second login screen was unusual.

I am running XFCE 4.12 on Slackware 14.1, with xcreensaver 5.40.

The first login screen to exit the screensaver was normal. However, the screen then became black, and when I moved the mouse or typed a key it became white with a black square and some text saying something like

Blank screensaver, enter your password to login or click the icon to lock

along with the machine name.

However I cannot find any "blank screensaver" in xscreensaver's list, and it didn't look like an xscreensaver anyway (no login box, the login form took the whole screen).

Is such a screensaver known ? And could I have triggered its shortcut with random keys ? Call me paranoid, but I wonder if it might be some keylogger…

  • 1
    That text sounds like what xlock used to say. Perhaps it got run as well?
    – alanc
    Apr 7, 2019 at 3:08
  • @alanc That's it ! Make your comment an answer so I can accept it. Apr 7, 2019 at 14:26

2 Answers 2


Read the manpage: https://www.jwz.org/xscreensaver/man1.html

Or type

man 1 xscreensaver

Search for blank - I found it almost immediately under the mode option.

    blank   When blanking the screen, just go black: don't run any graphics hacks.

Enjoy the other, prettier hacks!

  • 1
    I felt dumb for a minute, but after testing this mode doesn't seem to correspond to my issue : the password prompt is the same GUI box as with other xscreensavers. Mar 27, 2019 at 7:50
  • If this doesn't look the same then it very likely isn't xscreensaver, because that is drawn using a very limited part of the code (intentionally, to reduce the dependence on external libraries) although it can be styled. Does this happen every time? What happens if you type the wrong password into the second dialog? If it happens always, try creating another user and see if it happens for that account. Check your login scripts, .local, any desktop startup stuff.
    – Rich
    Mar 28, 2019 at 16:22
  • No, it happened only once. It didn't look like an X screensaver anyway, it rather looked like what a framebuffer screensaver could look like. Mar 28, 2019 at 16:25

As found by alanc, this is actually a known screensaver : xlock. I don't know why it took precedence once, but it seems to run automatically (under Slackware 14.1) when XScreenSaver isn't running : I had to kill XScreenSaver yesterday for some reason and it ran since.

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