How do I mount the USB stick containing the installer in Rescue Mode?

[Stella Ashburne <rewefie@gmx.com>]

Debian Bullseye's installer is on a USB stick and I used it to boot into Rescue Mode. If it's of any relevance, the partition table type is GPT, with UEFI+Secure Boot enabled.

After booting into Rescue Mode and filling out the required details onscreen, I chose /dev/perfect-vg/root as the device to use as root file system. If you may recall, the volume group perfect-vg is LUKS-encrypted.

When asked if I wanted to mount the separate /boot/efi partition, I entered No.

Next, I entered Executive a shell in /dev/perfect-vg/root

I typed the command nano /etc/apt/sources.list and commented out all the lines therein.

I added the the following line:

deb [trusted=yes] file:/media/myusb bullseye main

I saved the sources.list file.

I created a directory called /media/myusb and issued the following command to mount the USB stick to it:

mount /dev/sdb1 /media/myusb

The error message is:

mount: /media/myusb: /dev/sdb1 already mounted or mount point busy

Below are the results of cat /etc/fstab

<file system>                  <mount point>  <type>   <options>    <dump>   <pass>
/dev/mapper/perfect--vg-root   /              ext4     errors-remount-ro   0   1
/boot/efi was on /dev/sda1 during installation
UUID=A30E-2C33    /boot/efi     vfat    umask=0077      0      1
/dev/mapper/perfect--vg-swap    none       swap    sw   0      0
/dev/sr0      /media/cdrom0     udf, iso9660 user, noauto   0  0
/media/myusb

I appreciate your help in this matter.