Non interactive ftp for Linux users

FTP. Yes, people are still using it.

1.  non interactive ftp login:
   

   $ ~/.netrc
   machine server_name/ip
   login username
   password password
   
   $ chmod 600 ~/.netrc

   Now you can simply ftp to said machine and it will auto-login.
   
   
2.  Copying a file to the ftp server:
   

   • echo put FILE.ext | ftp server_name
     or
   •  curl -T FILE.ext ftp://server_name --user username:password

Checking your NIC is connected using bash

A simple yet effective way to test your network adapters connection status using  command line.

Requires: ethtool


# ifconfig -a|grep eth|while read line;do echo ${line%% *} && ethtool ${line%% *}|grep Link;done

Slow ssh in RHEL/CentOS

It's everywhere and so it's also here, if ssh to Red Hat or CentOS takes forever, here's a quick fix:

# sed -i 's/^#UseDNS yes/UseDNS no/g' /etc/ssh/sshd_config
# sed -i 's/^#GSSAPIAuthentication no/GSSAPIAuthentication no/g' /etc/ssh/sshd_config
# sed -i 's/^GSSAPIAuthentication yes/#GSSAPIAuthentication yes/g' /etc/ssh/sshd_config
# service sshd restart

BASH CLI turn monitor off / blank screen

So you want to get your screen blank or get your monitor into standby mode from the CLI?
Add the following to your .bashrc:

alias blank='sleep 1 && xset dpms force standby'

From there on, just use the command blank from your terminal.

Quickly add rules to IPTABLES on CentOS/RHEL 5.x using a script

Older iptables lack the -C switch so you have to use bash to check whether a rule already exists before appending it. Works like this:

if [ ! "`iptables-save | grep 'dport 21'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 21 -j ACCEPT;fi
if [ ! "`iptables-save | grep 'dport 22'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 22 -j ACCEPT;fi
if [ ! "`iptables-save | grep 'dport 80'`" ]; then iptables -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT;fi
service iptables save

Probably not the most elegant solution, but it works. 

Quickly disable SELinux in a setup script

So we all know how to disable SELinux manually, but what about doing so as part of a setup script?
Easy, got to love sed!

Setenforce 0

sed -i 's/^SELINUX=.*/SELINUX=disabled/g' /etc/sysconfig/selinux && cat /etc/sysconfig/selinux

Repeat on /etc/selinux/config for Centos 7

Key exchange for passwordless rsync, scp, ssh...

There are so many answers out there but this is probably the best one I've seen:
http://troy.jdmz.net/rsync