initial commit:

This commit is contained in:
James Swineson 2019-04-09 15:51:15 +08:00
commit 3883e36abc

146
menhera.sh Executable file
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#!/bin/bash
set -Eeuxo pipefail
# config
WORKDIR="/tmp/menhera"
ROOTFS="https://images.linuxcontainers.org/images/debian/stretch/amd64/default/20190406_05:24/rootfs.squashfs"
# internal global variables
OLDROOT="/"
NEWROOT=""
# https://stackoverflow.com/a/3232082/2646069
confirm() {
# call with a prompt string or use a default
read -r -p "${1:-Are you sure? [y/N]} " response
case "$response" in
[yY][eE][sS]|[yY])
true
;;
*)
false
;;
esac
}
sync_filesystem() {
echo "Syncing..."
sync
sync
}
prepare_environment() {
echo "Loading kernel modules..."
modprobe overlay
modprobe squashfs
echo "Creating workspace in '${WORKDIR}'..."
# workspace
mkdir -p "${WORKDIR}"
mount -t tmpfs tmpfs "${WORKDIR}"
# new rootfs
mkdir -p "${WORKDIR}/newroot"
# readonly part of new rootfs
mkdir -p "${WORKDIR}/newrootro"
# writeable part of new rootfs
mkdir -p "${WORKDIR}/newrootrw"
# overlayfs workdir
mkdir -p "${WORKDIR}/overlayfs_workdir"
echo "Downloading temporary rootfs..."
wget "${ROOTFS}" -O "${WORKDIR}/rootfs.squashfs"
}
mount_new_rootfs() {
echo "Mounting temporary rootfs..."
mount -t squashfs "${WORKDIR}/rootfs.squashfs" "${WORKDIR}/newrootro"
mount -t overlay overlay -o rw,lowerdir="${WORKDIR}/newrootro",upperdir="${WORKDIR}/newrootrw",workdir="${WORKDIR}/overlayfs_workdir" "${WORKDIR}/newroot"
NEWROOT="${WORKDIR}/newroot"
}
install_software() {
echo "Installing OpenSSH Server into new rootfs..."
DEBIAN_FRONTEND=noninteractive chroot "${NEWROOT}" apt-get update -y
DEBIAN_FRONTEND=noninteractive chroot "${NEWROOT}" apt-get -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" install -y ssh
}
copy_config() {
echo "Copying important config into new rootfs..."
cp -ax "${OLDROOT}/etc/resolv.conf" "${NEWROOT}/etc"
cp -axr "${OLDROOT}/etc/ssh" "${NEWROOT}/etc"
cp -ax "${OLDROOT}/etc/{passwd,shadow}" "${NEWROOT}/etc"
cp -axr "${OLDROOT}/root/.ssh" "${NEWROOT}/root"
chroot "${NEWROOT}" chsh -s /bin/bash root
}
swap_root() {
echo "Swapping rootfs..."
# prepare future mount point for our old rootfs
mkdir -p "${WORKDIR}/newroot/mnt/oldroot"
mount --make-rprivate /
# swap root
pivot_root "${WORKDIR}/newroot" "${WORKDIR}/newroot/mnt/oldroot"
OLDROOT="/mnt/oldroot"
NEWROOT="/"
# move mounts
for i in dev proc sys run; do mount --move "${OLDROOT}/$i" "${NEWROOT}/$i"; done
mount -t tmpfs tmpfs "${NEWROOT}/tmp"
}
clear_processes() {
echo "Restarting SSH daemon..."
systemctl restart ssh
echo "Restarting systemd..."
systemctl daemon-reexec --no-block
sleep 15
echo "Killing all programs still using the old root..."
fuser -kvm "${OLDROOT}" -15
sleep 15
fuser -kvm "${OLDROOT}" -9
sleep 3
echo "Disabling swap..."
swapoff -a
}
unmount_old_rootfs() {
echo "Unmounting old rootfs..."
umount "${OLDROOT}"
}
# main procedure
if [[ $EUID -ne 0 ]]; then
echo "This script must be run as root"
exit 1
fi
echo -e "We will start a temporary RAM system as your recovery environment."
echo -e "Note that this script will kill programs and umount filesystems without prompting."
echo -e "Please confirm:"
echo -e "\tYou have closed all programs you can, and backed up all important data"
echo -e "\tYou can SSH into your system as root user"
confirm || exit -1
sync_filesystem
prepare_environment
mount_new_rootfs
install_software
copy_config
swap_root
echo -e "If you are connecting from SSH, please create a second session to this host and confirm you can get a shell."
echo -e "After your confirmation, we are going to kill the old SSH server."
confirm || exit -1
clear_processes
unmount_old_rootfs