[SOLVED] Debian not excepting password when screen is locked unless i restart.

TokTok · 07-13-2020, 08:06 PM

Does anyone have a solution or explanation to this problem. My problem is that when i leave Debian on for several hours with the default screen saver on it won`t take the password but if i re-start or re-boot it does like it normally would. Yes, i know the password & entered it several times but it would not take it ** Same password ** until re-start.

jefro · 07-13-2020, 08:10 PM

Did it ever work correctly?

TokTok · 07-13-2020, 08:16 PM

Quote:

Originally Posted by jefro

Did it ever work correctly?

It`s a new install only a few days old. I think it has been doing it from the beginning i noticed it when i leave it on several hours with no activity.

shruggy · 07-14-2020, 01:43 AM

I've had once a similar problem with Xubuntu 20.04. Logging in on a virtual console (Ctrl+Alt+F1) and issuing xfce4-screensaver-command --exit helped. Didn't investigate it any further.

There is xdg-screensaver command to control screensaver from the command line. Most screensavers also have their respective *screensaver-command. E.g. xscreensaver-command, gnome-screensaver-command, mate-screensaver-command, etc.

Rebooting in this situation is unnecessary.

TokTok · 07-14-2020, 10:58 AM

Quote:

Originally Posted by shruggy

I've had once a similar problem with Xubuntu 20.04. Logging in on a virtual console (Ctrl+Alt+F1) and issuing xfce4-screensaver-command --exit helped. Didn't investigate it any further.

There is xdg-screensaver command to control screensaver from the command line. Most screensavers also have their respective *screensaver-command. E.g. xscreensaver-command, gnome-screensaver-command, mate-screensaver-command, etc.

Rebooting in this situation is unnecessary.

The screen saver is locked with a password like the system on startup so terminal is not accessible but re-starting is the only option.

shruggy · 07-14-2020, 11:48 AM

Unless you specifically configured X to disable them, virtual consoles should be accessible when the screen is locked. See the section Magic Backdoor Keystrokes in the xscreensaver(1) manual page:

Quote:

The XFree86 X server and the Linux kernel both trap certain magic keystrokes before X11 client programs ever see them. If you care about keeping your screen locked, this is a big problem.

Ctrl+Alt+Backspace

This keystroke kills the X server, and on some systems, leaves you at a text console. If the user launched X11 manually, that text console will still be logged in. To disable this keystroke globally and permanently, you need to set the DontZap flag in your xorg.conf or XF86Config or XF86Config-4 file, depending which is in use on your system. See XF86Config(5) for details.

Ctrl-Alt-F1, Ctrl-Alt-F2, etc.

These keystrokes will switch to a different virtual console, while leaving the console that X11 is running on locked. If you left a shell logged in on another virtual console, it is unprotected. So don't leave yourself logged in on other consoles. You can disable VT switching globally and permanently by setting DontVTSwitch in your xorg.conf, but that might make your system harder to use, since VT switching is an actual useful feature.

There is no way to disable VT switching only when the screen is locked. It's all or nothing.

Ctrl-Alt-KP_Multiply

This keystroke kills any X11 app that holds a lock, so typing this will kill xscreensaver and unlock the screen. This so-called "feature" showed up in the X server in 2008, and as of 2011, some vendors are shipping it turned on by default. How nice. You can disable it by turning off AllowClosedownGrabs in xorg.conf.

Alt-SysRq-F

This is the Linux kernel "OOM-killer" keystroke. It shoots down random long-running programs of its choosing, and so might might target and kill xscreensaver, and there's no way for xscreensaver to protect itself from that. You can disable it globally with:
Code:
echo 176 > /proc/sys/kernel/sysrq

This text is quite dated. Nowadays, most vendors (I believe Debian, too) ship their systems with Ctrl+Alt+Backspace and Ctrl+Alt+KP_Multiply disabled by default. But virtual consoles and the Magic SysRq key should be enabled in Debian.

TokTok · 07-15-2020, 04:23 PM

Quote:

Originally Posted by shruggy

Unless you specifically configured X to disable them, virtual consoles should be accessible when the screen is locked. See the section Magic Backdoor Keystrokes in the xscreensaver(1) manual page:

This text is quite dated. Nowadays, most vendors (I believe Debian, too) ship their systems with Ctrl+Alt+Backspace and Ctrl+Alt+KP_Multiply disabled by default. But virtual consoles and the Magic SysRq key should be enabled in Debian.

Thank`s i`ll look into it.
From your post the screen saver even though locked can be bypassed with the procedures above. Being a newbie can you specify what and where to post any specific code to disable the screen save from being bypassed ?

berndbausch · 07-15-2020, 07:49 PM

Quote:

Originally Posted by TokTok

From your post the screen saver even though locked can be bypassed with the procedures above.

Except for people who launch X from the command line (which is rare these days and which you are not doing), it can only be "bypassed" by entering username and password at the virtual console.