To access an encrypted Btrfs Arch Linux system from a live USB, you need to unlock the LUKS partition and mount each Btrfs subvolume before chrooting:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14

# Unlock the encrypted partition
cryptsetup open /dev/nvme0n1 cryptlvm

# Mount the root subvolume
mount -o subvol=@ /dev/mapper/cryptlvm /mnt

# Mount the home subvolume
mount -o subvol=@home /dev/mapper/cryptlvm /mnt/home

# Mount the log subvolume with nodatacow option
mount -o nodatacow,subvol=@var_log /dev/mapper/cryptlvm /mnt/var/log

# Chroot into the system
sudo arch-chroot /mnt

The cryptsetup open command unlocks the encrypted partition and maps it to /dev/mapper/cryptlvm. Each Btrfs subvolume needs to be mounted separately. The nodatacow option on /var/log prevents copy-on-write for log files. The arch-chroot command automatically handles mounting /proc, /sys, and /dev.