dotfiles/root/usr/local/bin/gentoo-chroot

#!/bin/sh

if [ "$EUID" -ne 0 ]; then
    echo "Must be ran as root"
    exit
fi

# Take user on the chrooted machine as 1st argument,
# this will be the logged user after chroot,
# default to root if none provided
if [ $# -ge 1 ]; then
    USERNAME="$1"
else
    USERNAME="root"
fi

MOUNT_POINT="/mnt/gentoo"
CLIENT_SCRIPT="/usr/local/bin/chroot-client"

# Make sure the partition is mounted according to fstab
mount "$MOUNT_POINT" 2> /dev/null

# Mount necessary directories for chroot to be possible
mount --types proc /proc "$MOUNT_POINT/proc"
mount --rbind /sys "$MOUNT_POINT/sys"
mount --make-rslave "$MOUNT_POINT/sys"
mount --rbind /dev "$MOUNT_POINT/dev"
mount --make-rslave "$MOUNT_POINT/dev"

# Chroot with custom script, if aviable
if [ -f "$MOUNT_POINT/$CLIENT_SCRIPT" ]; then
    chroot "$MOUNT_POINT" "$CLIENT_SCRIPT" "$USERNAME"
else
    # If we didn't find the script in the chroot environment
    # try to find it in this mahcine and copy it over
    if [ -f "$CLIENT_SCRIPT" ]; then
        echo "Client script not in chroot environment, copying"
        mkdir -p "$MOUNT_POINT/$(dirname $CLIENT_SCRIPT)"
        cp "$CLIENT_SCRIPT" "$MOUNT_POINT/$CLIENT_SCRIPTt"
        chroot "$MOUNT_POINT" "$CLIENT_SCRIPT" "$USERNAME"
    else
        echo "Unable to run chroot client script, proceeding manually"
        echo "You may need to run 'source /etc/profile' afterwards"

        # Try to obtain chroot user's default shell from /etc/passwd
        awkstring="BEGIN { FS=\":\" } /$USERNAME/ { print \$7 }"
        shell="$(cat /etc/passwd | awk "$awkstring")"

        if [ -n "$shell" ]; then
            echo "Found user's shell, trying to chroot with it ($shell)"
            chroot "$MOUNT_POINT" "$shell" --login
        else
            echo "Unable to find user in chroot's /etc/passwd, using root with bash shell"
            chroot "$MOUNT_POINT" "/bin/bash" --login
        fi

    fi
fi

# Unmount recursively mounted directories
umount -l "$MOUNT_POINT/dev{/shm,/pts,}"
umount -R "$MOUNT_POINT"

# Remount partition accordingly to fstab
# (the above umountings will unmount gentoo completely,
# which means that remounting is necessary)
mount "$MOUNT_POINT"