X Server no respond

You change run level to 3:
$ su -
password
# init 3

That will stop X.

To get back to normal with a GUI, change to runlevel 5:
# init 5

Improve boot and running performance

 

1, Step 1, figure out the most resource consuming service

dmesg

systemd-analyze blame:  Show the service on the boot.

2,Step 2 stop the service

systemctl disable bluetooth.service

To disable the service.

I disabled

• bluetooth.service,
• auditd.service,
• firewalld.service
• modemManager.service

3. uninstall unnecessary software.

 

About the NetworkManager-wait-online.service

 

The command $ systemctl disable NetworkManager-wait-online.service did not work,

but the $ systemctl mask NetworkManager-wait-online.service worked.

 

 

Systemd

 

SYNOPSIS

       systemd [OPTIONS...]

       init [OPTIONS...] {COMMAND}

DESCRIPTION

       systemd is a system and service manager for Linux operating systems.When run as first process on boot (as PID 1), it acts as init system
       that brings up and maintains userspace services.

       For compatibility with SysV, if systemd is called as init and a PID that is not 1, it will execute telinit and pass all command line
       arguments unmodified. That means init and telinit are mostly equivalent when invoked from normal login sessions. See telinit(8)
       for more information.

       When run as a system instance, systemd interprets the configuration file system.conf and the files in system.conf.d directories; when run
       as a user instance, systemd interprets the configuration file user.conf and the files in user.conf.d directories. See
       systemd-system.conf(5) for more information.

For more information, check out http://man7.org/linux/man-pages/man1/init.1.html