[1] It's possible to display services' status like follows.
[root@localhost ~]# systemctl -t service
UNIT LOAD ACTIVE SUB DESCRIPTION
auditd.service loaded active running Security Auditing Service
crond.service loaded active running Command Scheduler
dbus-daemon.service loaded active running D-Bus System Message Bus
dovecot.service loaded active running Dovecot IMAP/POP3 email server
dracut-shutdown.service loaded active exited Restore /run/initramfs on shutdown
firewalld.service loaded active running firewalld - dynamic firewall daemon
[email protected] loaded active running Getty on tty1
httpd.service loaded active running The Apache HTTP Server
import-state.service loaded active exited Import network configuration from initramfs
...
[2] List of all services.
[root@localhost ~]# systemctl list-unit-files -t service
UNIT FILE STATE
arp-ethers.service disabled
auditd.service enabled
[email protected] enabled
blk-availability.service disabled
bluetooth.service enabled
brltty.service disabled
[email protected] static
canberra-system-bootup.service disabled
canberra-system-shutdown-reboot.service disabled
canberra-system-shutdown.service disabled
[email protected] static
console-getty.service disabled
[email protected] static
cpupower.service disabled
crond.service enabled
...
[3] Stop and turn OFF auto-start setting for a service if you don'd need it. (it's bluetooth as an example below)
[root@localhost ~]# systemctl stop bluetooth
[root@localhost ~]# systemctl disable bluetooth
[4] View the status of a service.
[root@localhost ~]# systemctl status crond
● crond.service - Command Scheduler
Loaded: loaded (/usr/lib/systemd/system/crond.service; enabled; vendor preset: enabled)
Active: active (running) since Fri 2021-09-24 03:30:06 +03; 18h ago
Main PID: 1755 (crond)
Tasks: 1 (limit: 4915)
Memory: 2.1M
CGroup: /system.slice/crond.service
└─1755 /usr/sbin/crond -n
Sep 24 13:01:01 localhost.localdomain CROND[30121]: (root) CMD (run-parts /etc/cron.hourly)
Sep 24 14:01:01 localhost.localdomain CROND[22819]: (root) CMD (run-parts /etc/cron.hourly)
...
[5] Start a service and add it to startup services.
[root@localhost ~]# systemctl start httpd
[root@localhost ~]# systemctl enable httpd
Created symlink /etc/systemd/system/multi-user.target.wants/httpd.service → /usr/lib/systemd/system/httpd.service.
[6] Restart a service.
[root@localhost ~]# systemctl restart crond
[7] Check that a service has been added to the startup services.
[root@localhost ~]# systemctl is-enabled postfix
enabled
[8] Check the running status of a service.
[root@localhost ~]# systemctl is-active bluetooth
inactive