The Chroot Automator (mount-chroot.sh)

mount-chroot.sh

#!/bin/bash

# Usage: sudo ./mount-chroot.sh /dev/mapper/ubuntu--vg-root /dev/sda2 /dev/sda1
# Params: 1: Root device, 2: Boot partition (optional), 3: EFI partition (optional)

#Execution Workflow
#Unlock LUKS first:
#cryptsetup luksOpen /dev/sda3 crypt_root

#Run script:
#chmod +x mount-chroot.sh
#sudo ./mount-chroot.sh /dev/mapper/crypt_root /dev/sda2 /dev/sda1

ROOT_DEV=$1
BOOT_DEV=$2
EFI_DEV=$3
TARGET="/mnt/chroot"

if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root"
   exit 1
fi

if [[ -z "$ROOT_DEV" ]]; then
    echo "Usage: $0 <root_dev> [boot_dev] [efi_dev]"
    exit 1
fi

echo "--- Preparing Chroot Environment at $TARGET ---"

# 1. Mount Root
mkdir -p $TARGET
mount $ROOT_DEV $TARGET

# 2. Mount Boot/EFI if provided
if [[ -n "$BOOT_DEV" ]]; then
    mount $BOOT_DEV $TARGET/boot
fi

if [[ -n "$EFI_DEV" ]]; then
    mount $EFI_DEV $TARGET/boot/efi
fi

# 3. Bind API Filesystems
echo "--- Binding Kernel API Filesystems ---"
for dir in /dev /dev/pts /proc /sys /run; do
    mount --bind $dir $TARGET$dir
done

# 4. Copy DNS config to ensure networking inside chroot
cp /etc/resolv.conf $TARGET/etc/resolv.conf

echo "--- Entering Chroot ---"
chroot $TARGET /bin/bash

# 5. Cleanup after exiting chroot
echo "--- Chroot exited. Unmounting... ---"
umount -l $TARGET/dev/pts
umount -l $TARGET/dev
umount -l $TARGET/proc
umount -l $TARGET/sys
umount -l $TARGET/run
if [[ -n "$EFI_DEV" ]]; then umount $TARGET/boot/efi; fi
if [[ -n "$BOOT_DEV" ]]; then umount $TARGET/boot; fi
umount $TARGET
echo "--- Done ---"