Switching keyboard layout on Ubuntu 13.10

Found this after digging around in AskUbuntu:

It's still possible to make the change from the command line using dpkg. Credit goes to this site: http://www.humans-enabled.com/2013/10/ubuntu-1310-enable-controlaltbackspace.html. To sum up what's written there, you can open a terminal and enter

$ sudo dpkg-reconfigure keyboard-configuration

This will take you through a series of options for the keyboard; for the first 4 or 5 just hit enter to keep things as is, and you'll end up with the option to enable Ctrl-Alt-Backspace.

Quick ping-scanning a network using bash

So you want to know who answers to pings in said network or IP range?
Certainly not the best way to map a network, but it's useful enough to find a forgotten IP number without having to check with your DHCP:

$ for ip in 10.0.0.{000..255};do ping -c1 -t1 $ip > /dev/null 2>&1 && echo "${ip} is up" & done|grep up|sort

This method can also be used to run multiple commands in multiple terminal windows by using gnome-terminal -e "your command here".

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.