reboot-guard

Block systemd-initiated poweroff/reboot/halt until configurable condition checks pass

Requirements

• Python 2.7
• systemd
• Can be launched from a simple systemd service or run manually

Interactive walk-thru: ONE-SHOT

1. Download and execute rguard without any condition checks to confirm it really can block shutdown.

   [root]# cd /usr/sbin
   [root]# curl -kO https://raw.githubusercontent.com/ryran/reboot-guard/master/rguard
     % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                    Dload  Upload   Total   Spent    Left  Speed
   100 16575  100 16575    0     0  54536      0 --:--:-- --:--:-- --:--:-- 54702
   [root]# ll rguard
   -rwxr-xr-x. 1 root root 16575 Sep  1 02:46 rguard
   [root]# rguard -1
   WARNING: ☹  Blocked poweroff.target
   WARNING: ☹  Blocked reboot.target
   WARNING: ☹  Blocked halt.target
   [root]# 
   

2. Try to reboot/shutdown/halt and fail. Note that the old legacy commands (halt, shutdown, reboot) trigger wall messages regardless.

   [root]# systemctl reboot
   Failed to issue method call: Operation refused, unit reboot.target may be requested by dependency only.
   [root]# shutdown -h now
   Failed to issue method call: Operation refused, unit poweroff.target may be requested by dependency only.
   
   Broadcast message from root@localhost on pts/0 (Mon 2015-08-31 02:28:05 EDT):
   
   The system is going down for power-off NOW!
   [root]#
   

3. Disable the blocks.

   [root]# rguard -0
   WARNING: ☻  Unblocked poweroff.target
   WARNING: ☻  Unblocked reboot.target
   WARNING: ☻  Unblocked halt.target
   [root]# 
   

Interactive walk-thru: CONDITION CHECKS

1. Execute rguard with a tiny sleep-interval and 2 simple checks.

   [root]# rguard --interval 15 --unit atd --require-file /run/.require &
   [1] 23317
   WARNING: ☹  Failed a condition-check
   WARNING: ☹  Blocked poweroff.target
   WARNING: ☹  Blocked reboot.target
   WARNING: ☹  Blocked halt.target
   [root]# 
   

2. The conditions we set meant shutdown will be blocked while atd is active and while /run/.require does not exist, so fix that and rguard will immediately unblock shutdown.

   [root]# systemctl is-active atd
   active
   [root]# systemctl stop atd
   [root]# touch /run/.require
   WARNING: ☻  Passed all condition-checks
   WARNING: ☻  Unblocked poweroff.target
   WARNING: ☻  Unblocked reboot.target
   WARNING: ☻  Unblocked halt.target
   [root]# fg
   rguard --interval 15 --unit atd --require-file /run/.require
   ^C
   WARNING: Gracefully exiting due to receipt of signal 2
   

Instructions for daemon service

1. Install the latest rpm from Releases or setup yum repo:
   • yum/dnf install http://people.redhat.com/rsawhill/rpms/latest-rsawaroha-release.rpm
   • yum/dnf install reboot-guard
2. If you want the service to always block reboot/shutdown, requiring the service to be manually stopped or killed, simply run systemctl daemon-reload; systemctl enable rguard --now and you are done; otherwise, continue to next step
3. Play with the options until you get them how you want them (see help page: rguard --help)
4. Copy /usr/lib/systemd/system/rguard.service to /etc/systemd/system and set the ExecStart= directive to your liking
5. Run: systemctl daemon-reload; systemctl enable rguard --now
6. Check systemctl status rguard -n50 or use journalctl -fu rguard to keep an eye on logs (turn up the --loglevel if necesary)
7. Tweak rguard.service as required, and then re-run systemctl daemon-reload; systemctl restart rguard
8. Give feedback by posting to the Issue Tracker

Help page

usage: rguard [-1 | -0] [-f FILE] [-F FILE] [-u UNIT] [-c CMD] [-a ARGS]
              [-r COMMAND] [-h] [-i SEC] [-n] [-x]
              [-v {debug,info,warning,error}] [-t]

Block systemd-initiated shutdown until configurable condition checks pass

SET AND QUIT:
  Execute a single action with no condition checks.

  -1, --install-guard   Install reboot-guard and immediately exit
  -0, --remove-guard    Remove reboot-guard (if present) and immediately exit

CONFIGURE CONDITIONS:
  Establish what condition checks must pass to allow shutdown.
  Each option may be specified multiple times.

  -f, --forbid-file FILE
                        Prevent shutdown while FILE exists
  -F, --require-file FILE
                        Prevent shutdown until FILE exists
  -u, --unit UNIT       Prevent shutdown while systemd UNIT is active
  -c, --cmd CMD         Prevent shutdown while CMD exactly matches at least 1
                        running process
  -a, --args ARGS       Prevent shutdown while ARGS exactly matches the full
                        cmd+args of at least 1 running process
  -r, --run COMMAND     Prevent shutdown while execution of COMMAND fails;
                        prefix COMMAND with '!' to prevent shutdown while
                        execution succeeds (MORE: Prefix COMMAND with '@' to
                        execute it as a shell command, e.g., to use pipes '|'
                        or other logic; examples: '@cmd|cmd' or '!@cmd|cmd')

GENERAL OPTIONS:

  -h, --help            Show this help message and exit
  -i, --interval SEC    Modify the sleep interval between condition checks
                        (default: 60 seconds)
  -n, --ignore-signals  Ignore the most common signals (HUP, INT, QUIT, USR1,
                        USR2, TERM), in which case a graceful exit requires
                        the next option or else SIGKILL
  -x, --exit-on-pass    Exit (and remove reboot-guard) the first time all
                        condition checks pass
  -v, --loglevel {debug,info,warning,error}
                        Specify minimum message type to print (default:
                        warning)
  -t, --timestamps      Enable timestamps in message output (not necessary if
                        running as systemd service)

EXAMPLES:
  As mentioned above, all of the condition-checking options can be used
  multiple times. All specified checks must pass to allow shutdown.

  rguard --forbid-file /shutdown/prevented/if/this/file/exists

  rguard --require-file /shutdown/prevented/until/this/file/exists

  rguard --cmd some-cmd-name-which-when-running-prevents-shutdown
           * e.g., 'bash' or 'firefox'

  rguard --args 'syndaemon -i 1.0 -t -K -R'
           * Prevent shutdown if this exact cmd + args are found running

  rguard --run 'ping -c2 -w1 -W1 10.0.0.1'
           * Allow shutdown only if single command (ping in this case) succeeds

  rguard --run '!ping -c2 -w1 -W1 10.0.0.1'
           * Allow shutdown only if single command FAILS

  rguard --run '!findmnt /mnt'
           * Allow shutdown if nothing mounted at mountpoint

  rguard --run '@some_cmd | some_other_cmd; another_cmd'
           * Allow shutdown only if last cmd in shell succeeds
           * When using '@', full shell syntax is supported
           * e.g.: '|', '&&', '||', ';', '>', '>>', '<', etc

  rguard --run '!@lsof -i:ssh | grep -q ESTABLISHED'
           * Allow shutdown only if shell commands FAIL
           * In this example, only if there are no established ssh connections