nixpkgs/modules/system/activation/switch-to-configuration.sh

#! @shell@

set -e
export PATH=/empty
for i in @path@; do PATH=$PATH:$i/bin:$i/sbin; done
action="$1"

if ! test -e /etc/NIXOS; then
    echo "This is not a NixOS installation (/etc/NIXOS) is missing!"
    exit 1
fi

if test -z "$action"; then
    cat <<EOF
Usage: $0 [switch|boot|test]

switch: make the configuration the boot default and activate now
boot:   make the configuration the boot default
test:   activate the configuration, but don't make it the boot default
EOF
    exit 1
fi

# Install or update the bootloader.
if [ "$action" = "switch" -o "$action" = "boot" ]; then
    
    if [ "@bootLoader@" = "grub" ]; then
        
      if [ -n "@grubDevice@" ]; then
          mkdir -m 0700 -p /boot/grub
          @menuBuilder@ @out@

          if [ "@grubDevice@" != nodev ]; then
              
              # If the GRUB version has changed, then force a reinstall.
              oldGrubVersion="$(cat /boot/grub/version 2>/dev/null || true)"
              newGrubVersion="@grubVersion@"

              if [ "$NIXOS_INSTALL_GRUB" = 1 -o "$oldGrubVersion" != "$newGrubVersion" ]; then
                  echo "installing the GRUB bootloader..."
                  @grub@/sbin/grub-install "$(readlink -f "@grubDevice@")" --no-floppy
                  echo "$newGrubVersion" > /boot/grub/version
              fi
          fi
          
      else
          echo "Warning: don't know how to make this configuration bootable; please set \`boot.loader.grub.device'." 1>&2
      fi
      
    elif [ "@bootLoader@" = "generationsDir" ]; then
        @menuBuilder@ @out@
    else
        echo "Warning: don't know how to make this configuration bootable; please enable a boot loader." 1>&2
    fi

    if [ -n "@initScriptBuilder@" ]; then
        @initScriptBuilder@ @out@
    fi
fi

# Activate the new configuration.
if [ "$action" = "switch" -o "$action" = "test" ]; then

    oldVersion=$(cat /var/run/current-system/upstart-interface-version 2> /dev/null || echo 0)
    newVersion=$(cat @out@/upstart-interface-version 2> /dev/null || echo 0)

    if test "$oldVersion" -ne "$newVersion"; then
        cat <<EOF
Warning: the new NixOS configuration has an Upstart version that is
incompatible with the current version.  The new configuration won't
take effect until you reboot the system.
EOF
        exit 1
    fi

    oldJobs=$(readlink -f /etc/static/init)
    newJobs=$(readlink -f @out@/etc/init)

    stopJob() {
        local job=$1
        initctl stop "$job" || true
    }

    # Stop all services that are not in the new Upstart
    # configuration.
    for job in $(cd $oldJobs && ls *.conf); do
        job=$(basename $job .conf)
        if ! test -e "$newJobs/$job.conf"; then
            echo "stopping $job..."
            stopJob $job
        fi
    done

    # Activate the new configuration (i.e., update /etc, make
    # accounts, and so on).
    echo "activating the configuration..."
    @out@/activate @out@

    # Make Upstart reload its jobs.
    initctl reload-configuration

    # Start all new services and restart all changed services.
    for job in $(cd $newJobs && ls *.conf); do

        job=$(basename $job .conf)
        
        # Hack: skip the shutdown and control-alt-delete jobs.
        # Another hack: don't restart the X server (that would kill all the clients).
        # And don't restart dbus, since that causes ConsoleKit to
        # forget about current sessions.
        # Idem for the emergeny-shell, because its `console owner'
        # line screws up the X server.
        # Idem for xendomains because we don't want to save/restore
	# Xen domains unless we have to.
        # TODO: Jobs should be able to declare that they should not be
	# auto-restarted.
        if echo "$job" | grep -q "^shutdown$\|^control-alt-delete$\|^xserver$\|^dbus$\|^disnix$\|^emergency-shell$\|^xendomains$\|^udevtrigger$\|^drbd-down$"; then continue; fi

        if ! test -e "$oldJobs/$job.conf"; then
            echo "starting $job..."
            initctl start "$job" || true
        elif test "$(readlink "$oldJobs/$job.conf")" != "$(readlink "$newJobs/$job.conf")"; then
            echo "restarting $job..."
            stopJob $job
            initctl start "$job" || true
        fi
    done

    # Signal dbus to reload its configuration.
    dbusPid=$(initctl status dbus 2> /dev/null | sed -e 's/.*process \([0-9]\+\)/\1/;t;d')
    [ -n "$dbusPid" ] && kill -HUP "$dbusPid"
    
fi