查看/etc/inittab中的设置

[root@dns-a ~]# cat /etc/inittab 
# inittab is no longer used when using systemd.
#
# ADDING CONFIGURATION HERE WILL HAVE NO EFFECT ON YOUR SYSTEM.
#
# Ctrl-Alt-Delete is handled by /usr/lib/systemd/system/ctrl-alt-del.target
#
# systemd uses 'targets' instead of runlevels. By default, there are two main targets:
#
# multi-user.target: analogous to runlevel 3
# graphical.target: analogous to runlevel 5
#
# To view current default target, run:
# systemctl get-default
#
# To set a default target, run:
# systemctl set-default TARGET.target
#

根据/etc/inittab中的提示，ctrl+alt+del关机的配置是在/usr/lib/systemd/system/ctrl-alt-del.target中，查看此文件内容如下：

[root@dns-a ~]# cat /usr/lib/systemd/system/ctrl-alt-del.target 
#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.

[Unit]
Description=Reboot
Documentation=man:systemd.special(7)
DefaultDependencies=no
Requires=systemd-reboot.service
After=systemd-reboot.service
AllowIsolate=yes
JobTimeoutSec=30min
JobTimeoutAction=reboot-force

[Install]
Alias=ctrl-alt-del.target

查看/usr/lib/systemd/system/ctrl-alt-del.target,其实是reboot.target文件的软链接

[root@dns-b ~]# ll /usr/lib/systemd/system/ctrl-alt-del.target
lrwxrwxrwx. 1 root root 13 Jul  9 22:27 /usr/lib/systemd/system/ctrl-alt-del.target -> reboot.target

因此，要想禁用ctrl+alt+del重启系统，只需要删除此软链接即可