Multiple Gateways to Server
nano /etc/network/interfaces
auto lo
iface lo inet loopbackauto eth0
iface eth0 inet static
address 10.0.0.52
netmask 255.255.255.0
gateway 10.0.0.1auto eth1
iface eth1 inet static
address 10.0.1.52
netmask 255.255.255.0
post-up route add 10.0.1.52 via 10.0.1.1 dev eth1
auto eth2
iface eth2 inet static
address 10.0.2.52
netmask 255.255.255.0
post-up route add 10.0.2.52 via 10.0.2.1 dev eth2

 

Restrict SSH Access to Specific IP for User
nano /etc/ssh/sshd_config
AllowUsers rene@11.22.33.44
OR
AllowUsers jim@11.22.33.*
OR
AllowUsers *@192.168.1.100

 

Copying files
cp file file.old

 

Copying folder with content
cp -R source destination

 

Install editor
yum install nano

 

Remove folder content
rm /path/to/directory/*

 

Create a File
cat > foo.txt

 

Delete all files and directories within the directory
rm -rf mydir