ssh環境での誤ったシステム停止を防ぐmolly-guard

$ apt-file search /sbin/shutdown
molly-guard: /sbin/shutdown
systemd-sysv: /sbin/shutdown
sysvinit-core: /sbin/shutdown

$ apt show molly-guard
Package: molly-guard
Version: 0.6.4
Priority: extra
Section: admin
Maintainer: Francois Marier <francois@debian.org>
Installed-Size: 57.3 kB
Depends: procps
Enhances: init, kexec-tools, mosh, openssh-server, pm-utils, systemd, sysvinit, upstart
Tag: implemented-in::shell, interface::commandline, network::server,
 protocol::ssh, role::program, scope::utility
Download-Size: 13.8 kB
APT-Manual-Installed: yes
APT-Sources: http://ftp.jp.debian.org/debian stretch/main amd64 Packages
Description: protects machines from accidental shutdowns/reboots
 The package installs a shell script that overrides the existing
 shutdown/reboot/halt/poweroff/coldreboot/pm-hibernate/pm-suspend* commands
 and first runs a set of scripts, which all have to exit successfully,
 before molly-guard invokes the real command.
 .
 One of the scripts checks for existing SSH sessions. If any of the four
 commands are called interactively over an SSH session, the shell script
 prompts you to enter the name of the host you wish to shut down. This should
 adequately prevent you from accidental shutdowns and reboots.
 .
 molly-guard diverts the real binaries to /lib/molly-guard/.  You can bypass
 molly-guard by running those binaries directly.

$ sudo apt install molly-guard
    :
package diverts others to: /lib/molly-guard/coldreboot
/sbin/halt
package diverts others to: /lib/molly-guard/halt
/sbin/pm-hibernate
/sbin/pm-suspend
/sbin/pm-suspend-hybrid
/sbin/poweroff
package diverts others to: /lib/molly-guard/poweroff
/sbin/reboot
package diverts others to: /lib/molly-guard/reboot
/sbin/shutdown
package diverts others to: /lib/molly-guard/shutdown

$ ls -l /sbin | grep molly
lrwxrwxrwx 1 root root        28 Aug 16  2016 coldreboot -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 halt -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 pm-hibernate -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 pm-suspend -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 pm-suspend-hybrid -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 poweroff -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 reboot -> /lib/molly-guard/molly-guard
lrwxrwxrwx 1 root root        28 Aug 16  2016 shutdown -> /lib/molly-guard/molly-guard

$ ls -lA /lib/molly-guard
total 48
-rwxr-xr-x 1 root root 18952 Feb 13  2017 halt
-rwxr-xr-x 1 root root  2767 Aug 16  2016 molly-guard
lrwxrwxrwx 1 root root     4 Feb 13  2017 poweroff -> halt
lrwxrwxrwx 1 root root     4 Feb 13  2017 reboot -> halt
-rwxr-xr-x 1 root root 23368 Feb 13  2017 shutdown

$ ls -lA /lib/molly-guard
total 4
lrwxrwxrwx 1 root root   14 Jun 14 05:20 halt -> /bin/systemctl
-rwxr-xr-x 1 root root 2767 Aug 16  2016 molly-guard
lrwxrwxrwx 1 root root   14 Jun 14 05:20 poweroff -> /bin/systemctl
lrwxrwxrwx 1 root root   14 Jun 14 05:20 reboot -> /bin/systemctl
lrwxrwxrwx 1 root root   14 Jun 14 05:20 shutdown -> /bin/systemctl

$ sudo shutdown -f -P -h +10 "kernel update (`uname -r`)"
W: molly-guard: SSH session detected!
Please type in hostname of the machine to shutdown: desktop
Good thing I asked; I won't shutdown debian ...
W: aborting shutdown due to 30-query-hostname exiting with code 1.

$ sudo shutdown -f -P -h +10 "kernel update (`uname -r`)"
W: molly-guard: SSH session detected!
Please type in hostname of the machine to shutdown: debian

Broadcast message from root@debian (pts/0) (Thu Sep 27 06:15:28 2018):

kernel update (4.9.0-3-amd64)
The system is going DOWN for system halt in 10 minutes!
^C
Shutdown cancelled.

$ sudo shutdown -f -P -h +10 'poweroff'
^C
Shutdown cancelled.