Managing services using systemd and sysV init

 ustlstops142 - Dev server. - Tops/Cathy.

Virtual server.

RHEL 7.9 - 

systemd -

unit files - /lib/systemd/system

.service - daemons

.timer

.target - user environmet

.slice

.socket -> network service

.mount - systemd doesn't needs /etc/fstab -> it can use .mount

/etc/systemd/system -> overreides /lib/systemd/system - make config changes only here

systemd is a binary - it is an executable that runs.

systemctl - controls systemd

systemctl start httpd

systemctl enable httpd -> puts a symlink in /etc/ for /usr/lib/systemd/system/httpd.service

systemctl disable httpd -> removes the symlink from /etc/ for httpd.server

systemctl status httpd -?

systemctl isolate multi-user.target

Managing services with systemd

Amazon Linux - uses CentOS06 - uses upstart - user sysV init

sysV init - starts process one by one.

systemd - starts process in parallel

===

$  ls -l | grep rc.*

# Please note that you must run 'chmod +x /etc/rc.d/rc.local' to ensure

$

$

rc.sysinit - systemV init

systemd - uses targets instead of runlevels -

==============

chkconfig - lets you turn on/off services at different run levels. - it defaults to run level 3 or 5.

chkconfig httpd on

chkconfig --level 35 httpd on

chkconfig --list

chkconfig --list| grep mysql

service start httpd