Saturday, July 3, 2021

Howto check Centos 7 and 8 common services

In Centos 7 and earlier, SysV manage Linux services. To list such services, 

config --list


Centos 7 and 8 uses Systemd to manage Linux services. The syntax for this command is

systemctl [OPTIONS...] COMMAND [UNIT...]

Centos 7 was a transition phase towards the newer Systemd, and it maintained a mix of service types.


Here are a list of common command to check Linux services.

List active systemd services

systemctl 



List all systemd services

systemctl -a

List only SysV services (centos 7 and older)

systemctl list-unit-files


List by service types

systemctl list-units --type service

systemctl list-units --type mount

Where

LOAD   = Reflects whether the unit definition was properly loaded.

ACTIVE = The high-level unit activation state, i.e. generalization of SUB.

SUB    = The low-level unit activation state, values depend on unit type.


Check status of a service

systemctl status sshd.service

sudo systemctl status nfs-server.service


To stop or start or restart a service

sudo systemctl stop nfs-server.service

sudo systemctl start nfs-server.service

sudo systemctl restart nfs-server.service


To determine service is active or enabled the following will return 0 (active) and non zero (disabled)

systemctl is-active sshd

systemctl is-enabled sshd

systemctl is-active nfs-server

systemctl is-enabled nfs-server


To list a service and its dependencies;

 systemctl list-dependencies nfs-server


List services and their number of running task, CPU percentage, memory usage and I/O continuously

systemd-cgtop


List services as above once

systemd-cgtop -n 1


To sort, use the following based on the column titles

systemd-cgtop -t 

systemd-cgtop -c

systemd-cgtop -m

systemd-cgtop -i


List services and their open ports

netstat -a

List services that use TCP and UDP and their open ports

netstat -tulpn


Display which user is used for a filename

fuser . -v


Display running service

top


Display running services in pretty formatting and enable F1-F10 commands.

htop






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