147 lines
4 KiB
Bash
Executable file
147 lines
4 KiB
Bash
Executable file
#!/bin/bash
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set -Eeuo pipefail
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# config
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WORKDIR="/tmp/menhera"
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ROOTFS="https://images.linuxcontainers.org/images/debian/stretch/amd64/default/20190409_05:24/rootfs.squashfs"
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# internal global variables
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OLDROOT="/"
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NEWROOT=""
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# https://stackoverflow.com/a/3232082/2646069
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confirm() {
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# call with a prompt string or use a default
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read -r -p "${1:-Are you sure? [y/N]} " response
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case "$response" in
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[yY][eE][sS]|[yY])
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true
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;;
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*)
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false
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;;
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esac
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}
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sync_filesystem() {
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echo "Syncing..."
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sync
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sync
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}
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prepare_environment() {
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echo "Loading kernel modules..."
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modprobe overlay
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modprobe squashfs
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echo "Creating workspace in '${WORKDIR}'..."
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# workspace
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mkdir -p "${WORKDIR}"
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mount -t tmpfs tmpfs "${WORKDIR}"
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# new rootfs
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mkdir -p "${WORKDIR}/newroot"
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# readonly part of new rootfs
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mkdir -p "${WORKDIR}/newrootro"
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# writeable part of new rootfs
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mkdir -p "${WORKDIR}/newrootrw"
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# overlayfs workdir
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mkdir -p "${WORKDIR}/overlayfs_workdir"
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echo "Downloading temporary rootfs..."
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wget -c "${ROOTFS}" -O "${WORKDIR}/rootfs.squashfs"
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}
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mount_new_rootfs() {
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echo "Mounting temporary rootfs..."
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mount -t squashfs "${WORKDIR}/rootfs.squashfs" "${WORKDIR}/newrootro"
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mount -t overlay overlay -o rw,lowerdir="${WORKDIR}/newrootro",upperdir="${WORKDIR}/newrootrw",workdir="${WORKDIR}/overlayfs_workdir" "${WORKDIR}/newroot"
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NEWROOT="${WORKDIR}/newroot"
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}
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install_software() {
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echo "Installing OpenSSH Server into new rootfs..."
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DEBIAN_FRONTEND=noninteractive chroot "${NEWROOT}" apt-get update -y
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DEBIAN_FRONTEND=noninteractive chroot "${NEWROOT}" apt-get -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" install -y ssh
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}
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copy_config() {
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echo "Copying important config into new rootfs..."
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! cp -ax "${OLDROOT}/etc/resolv.conf" "${NEWROOT}/etc"
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! cp -axr "${OLDROOT}/etc/ssh" "${NEWROOT}/etc"
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! cp -ax "${OLDROOT}/etc/"{passwd,shadow} "${NEWROOT}/etc"
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! cp -axr "${OLDROOT}/root/.ssh" "${NEWROOT}/root"
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chroot "${NEWROOT}" chsh -s /bin/bash root
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cat > "${NEWROOT}/etc/motd" <<EOF
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NOTICE
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This is a minimal RAM system created by menhera.sh. Feel free to format your disk, but don't blame anyone
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except yourself if you lost important files or your system is broken.
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Download menhera.sh at https://github.com/Jamesits/manhera.sh
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Have a lot of fun...
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EOF
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}
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swap_root() {
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echo "Swapping rootfs..."
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# prepare future mount point for our old rootfs
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mkdir -p "${WORKDIR}/newroot/mnt/oldroot"
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mount --make-rprivate /
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# swap root
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pivot_root "${WORKDIR}/newroot" "${WORKDIR}/newroot/mnt/oldroot"
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OLDROOT="/mnt/oldroot"
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NEWROOT="/"
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# move mounts
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for i in dev proc sys run; do mount --move "${OLDROOT}/$i" "${NEWROOT}/$i"; done
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mount -t tmpfs tmpfs "${NEWROOT}/tmp"
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}
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clear_processes() {
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echo "Restarting SSH daemon..."
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systemctl restart ssh
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echo "Disabling swap..."
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swapoff -a
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echo "Restarting systemd..."
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systemctl daemon-reexec --no-block
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sleep 15
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echo "Killing all programs still using the old root..."
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fuser -kvm "${OLDROOT}" -15
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# in most cases the parent process of this script will be killed, so goodbye
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}
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if [[ $EUID -ne 0 ]]; then
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echo "This script must be run as root"
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exit 1
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fi
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echo -e "We will start a temporary RAM system as your recovery environment."
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echo -e "Note that this script will kill programs and umount filesystems without prompting."
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echo -e "Please confirm:"
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echo -e "\tYou have closed all programs you can, and backed up all important data"
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echo -e "\tYou can SSH into your system as root user"
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confirm || exit -1
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sync_filesystem
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prepare_environment
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mount_new_rootfs
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copy_config
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install_software
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swap_root
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echo -e "If you are connecting from SSH, please create a second session to this host and confirm you can get a shell."
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echo -e "After your confirmation, we are going to kill the old SSH server."
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confirm || exit -1
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clear_processes
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