bug#37513: Subject: Installer finish backtrace, umount dispatch exception /mnt device busy

[free bird <freebird42@riseup.net>]

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Dear Maintainers,

Backtrace details are in attached screenshots.

What led to the problem(s):

Wired Net Installs onto old laptop 
(previously had Debian; wiping old install).

Install 1: 
Used guided encrypted partitioning, XFCE.
Seemed to go OK, except,
(was unclear which US keyboard to choose, 
no swap space option in guided partitioning, and
seemed verrrrry slow compared with Debian net installs).
Problems: Finished with "Installation Complete, Reboot" box displayed
over repeating "device-mapper: remove ioctl on cryptroot  failed: Device
or resource busy"
(white text on blue screen)
and was hung/frozen (could not hit "Reboot"). 

Actions after: Cycled power.
Seemed OK after restart, but subsequent guix install packages were all
source compilations (extremely slow), and only one /home/user/Directory
had been created for the user account. So it became apparent this
install would be abandoned.

Expected: Smooth, complete install.

Install 2:
Same as before, plus GNOME.
Everything went OK during the install, except
Problems: Install ended with backtrace display, and
after hitting OK it displayed start of new install.

Action taken: Instead, I Ctrl-Alt-Fx to TTY, shutdown as root, then
powered up again. 

Expected results: Message to go umount swap file, or successful forced
umount and/or option to reboot (not starting new install).

Final results: All seems mostly OK now, except
Guix installed packages are not added to Applications menu until after
reboot
(as reported for Mate in Distrowatch review).

Suspected cause of umount problem: 
During install, I Ctrl-Alt-Fx to TTY, and added 10 GB swap file, 
suspecting insufficient memory (2 GB).
Also ran top in TTY.

Hardware: x86_64, Intel Core 2 Duo on old ASUS laptop, 2 GB RAM, 120 GB
SSD.


PS. Other feedback (from long time Debian user perspective):

XFCE comes with few packages and plugins by default,
and has more limited plugins available to add (that I've found).

It would be nice to get a warning, "are you sure you want to spend that
much time" when packages to be installed will require compiling and take
forever (e.g. qutebrowser).

Not having a torbrowser-launcher (installer) available, 
or even being able to download and (simply) run torbrowser is...
disappointing.

PPS. It's probably all user error. :) Thanks for the interesting
experience!

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