Linux Commands Shutting Down, Re-Mounting, yum command

shutdown -h now
shutdown -h +15

Shut Down > Halt now or in 15 minutes.

shutdown -r now
shutdown -r +15

Shut Down > Restart now or in 15 minutes.

mount -o remount,rw /

nano /etc/yum.repos.d/CentOS-Base.repo

Under:
#additional packages that extend functionality of existing packages
[centosplus]

Change:
enabled=0
to:
enabled=1

or just type:
# yum update --enablerepo centosplus mysql-server mysql

yum list available
yum install packagename
yum update packagename
yum check-update
yum search packagename

yum update
yum update httpd
yum update openssl
yum update mysql-server mysql
yum update php

/etc/init.d/sshd start
/etc/init.d/httpd start
/etc/init.d/httpd restart
/etc/rc.d/init.d/mysqld start
or
# service httpd start
# service httpd stop
# service httpd reload

/etc/rc.d/init.d/mysqld start /etc/rc.d/init.d/mysqld stop /etc/rc.d/init.d/mysqld restart

# chkconfig --list httpd

# chkconfig --level 3 httpd on

# chkconfig --level 3 httpd off

reset to default configuration: # chkconfig --level 3 httpd reset