127 lines
3.9 KiB
Bash
Executable File
127 lines
3.9 KiB
Bash
Executable File
#!/bin/bash
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set -Eeuo pipefail
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# disable command path hashing as we are going to move fast and break things
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set +h
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WORKDIR="/tmp/menhera"
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MIRROR="https://iso.meson.cc/ultralite/archlinux"
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ROOTFS="${MIRROR}/iso/latest/arch/x86_64/airootfs.sfs"
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# internal global variables
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OLDROOT="/"
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NEWROOT=""
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[[ "$(uname -m)" == "x86_64" ]] || { echo "error: wrong arch $(uname -m) (not x86_64)"; exit 1; }
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PUBKEY="./key.pub"
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[ -f "$PUBKEY" ] || { echo "error: you should put your ssh public key at ${PUBKEY} in order to ssh with root account and this key later"; exit 1; }
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if [[ $EUID -ne 0 ]]; then
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echo "This script must be run as root"
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exit 1
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fi
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systemctl status > /dev/null || { echo "error: no systemd"; exit 1; }
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# helper functions
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# https://stackoverflow.com/a/3232082/2646069
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menhera::confirm() {
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# call with a prompt string or use a default
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read -r -p "${1:-Are you sure? [y/N]} " response
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case "$response" in
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[yY][eE][sS]|[yY])
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true
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;;
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*)
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false
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;;
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esac
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}
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echo -e "We will start a temporary RAM system as your recovery environment."
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echo -e "Note that this script will kill programs and umount filesystems without prompting."
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echo -e "Please confirm:"
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echo -e "\tYou have closed all programs you can, and backed up all important data"
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echo -e "\tYou can SSH into your system as root user"
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menhera::confirm || exit -1
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# fix possible PATH problems
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export PATH="$PATH:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
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echo "Loading kernel modules..."
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modprobe overlay
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modprobe squashfs
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sysctl kernel.panic=10
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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 -o size=100% tmpfs "${WORKDIR}"
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mkdir -p "${WORKDIR}/newroot" # where iso is stored
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mkdir -p "${WORKDIR}/newrootro" # lower
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mkdir -p "${WORKDIR}/newrootrw" # upper
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mkdir -p "${WORKDIR}/overlayfs_workdir" # work
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echo "Downloading temporary rootfs..."
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wget -O "${WORKDIR}/rootfs.squashfs" "${ROOTFS}"
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echo "Mounting temporary rootfs..."
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mount -t squashfs "${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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rm -f "${NEWROOT}/etc/resolv.conf"
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cat "${OLDROOT}/etc/resolv.conf" > "${NEWROOT}/etc/resolv.conf"
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install -DTm0600 <(cat "$PUBKEY") "${NEWROOT}/root/.ssh/authorized_keys"
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chmod 0700 "${NEWROOT}/root/.ssh"
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sync && sync # why sync twice? idk
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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" "${WORKDIR}/newroot/mnt/oldroot"
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OLDROOT="/mnt/oldroot"
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NEWROOT="/"
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# move mounts
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for i in dev proc sys run; do
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if [ -d "${OLDROOT}/$i" ]; then
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mount --move "${OLDROOT}/$i" "${NEWROOT}/$i"
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fi
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done
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mount -t tmpfs -o size=100% tmpfs "${NEWROOT}/tmp"
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mkdir -p "${WORKDIR}"
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mount --move "${OLDROOT}/${WORKDIR}" "${WORKDIR}"
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echo "Restarting SSH daemon..."
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systemctl daemon-reload
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systemctl is-active ssh && systemctl stop ssh || true
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systemctl restart sshd
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echo "Disabling swap..."
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swapoff -a
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echo "Restarting init process..."
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systemctl daemon-reexec
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systemctl --quiet is-system-running || true
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echo -e "If you are connecting from SSH, please create a second session to this host use root and"
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echo -e "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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if menhera::confirm; then
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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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else
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echo -e "Please manually issue a reboot to recover your old OS. If you believe there is a bug in menhera.sh, "
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echo -e "raise a ticket at https://github.com/Jamesits/menhera.sh/issues ."
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fi
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