The prompt screen for password to mount LUKS on boot is black

asked 2019-03-29 05:49:56 -0500

hacrot3000 gravatar image

updated 2019-03-31 22:39:14 -0500

I am using Fedora 29, I have a LUKS partition and want to mount it on boot with prompt password step. I did:

  • Add mapper in file /etc/crypttab:

data /dev/sda6 none luks

  • Add mount point in /etc/fstab

/dev/mapper/data /mnt/Data ext4 rw 0 0

  • Disable plymouth by run command

plymouth-set-default-theme -R details

When booting I see the detail log, not splash screen as normal. But on the enter decrypt password step I only see a black screen, no prompt, nothing on the screen. I just like enter my password into a black hole then press enter. If I entered on time, the disk will be decrypted and mounted correctly, some time it not be mounted: I am not sure it because I entered wrong password or not on right moment.

How can I make my Fedora show the password prompt instead of the black screen?


I found the problem only happen when I use 2 external monitor same time: one on VGA and other one on DisplayPort. If I only use the primary laptop's monitor or only use the VGA monitor, I can see the prompt for password. If I use 2 monitors on VGA and DisplayPort same time I only see the black screen.

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Checklist: 1. when your system is booted, do you see a not used "VGA:0" (or similar) display in the displaymanager? 2. Are u using lightdm or gdm ?

if you can answere:"yes"+"lightdm" remove lightdm, install gdm => solved.

rdtcustomercare gravatar imagerdtcustomercare ( 2019-03-30 14:59:37 -0500 )edit

Thank rdtcustomercare, I had just found that the display is black only when I use more than 2 monitors. I am using on a laptop with 2 external monitor, one on DisplayPort and other on VGA. If I only use the primary monitor or VGA it work well, I can see the password prompt message. If I plug 2 monitors it only show the black.

I am using gdm, not lightdm so I guess the problem is gdm not working well with 2 external monitors.

hacrot3000 gravatar imagehacrot3000 ( 2019-03-31 22:35:24 -0500 )edit

We had that with lightdm on a dell laptop with a "hidden" internal vga device, so any DM has some bugs to resolve ;)

rdtcustomercare gravatar imagerdtcustomercare ( 2019-04-01 04:37:21 -0500 )edit