When I fist saw this product I had an instance light-bulb moment, I could stop paying for a dynamic DNS service and build my own private one. As a broadband (DHCP) user I have a very basic requirement of needing to regularly update an A record so that I can find my pc

To bring my idea into fruition I began researching; I need a cli tool which I could run from cron on my linux box (to send the DNS update requests to rackspace). In my research I found rscurl, a cli tool to control cloud servers, as rackspace have a standard API for all their products I have been able to use rscurl to develop rsdns.

rsdns is a series of cli tools to adding/deleting/changing rackspace DNS records, as part of the tool development I have created a script called rsdns-dc.sh to run on my machine, below is a short how to:

How to get free dynamic dns from rackspace.

Pre-requisit: This is for linux/mac, if you want to do this on windows you’ll need bash, curl, awk, sed & dig installed – google is your friend.

The instructions below assume that you (a) have a domain and (b) have already changed your NS records to point to dns1.stabletransit.com & dns2.stabletransit.com.

Download the latest rsdns from gitgub and unpack somewhere, I like ~/bin/rsdns.

Go to your rackspace management portal and grap your username & API key (It’s under “Your Account” -> “API Access”)

Create a config file for rsdns (~/.rsdns_config) with your settings.

RSUSER=linickx
RSAPIKEY=123456
RSPATH=~/bin/rsdns/

You need your domain created on rackspace, you can either use rackspaces GUI to do this (It’s under “Hosting” -> “Cloud Servers” -> “serverabc” -> “DNS” ) or you can use rsdns, like so.

[LINICKX@SERVER rsdns]$./rsdns-domain.sh -d www.linickx.com -e spam@linickx.com

Once you have a domain setup you need an A record, this step was a deliberate design to avoid any rouge cron jobs from creating a million records, the dynamic client will only update an existing record – not create a new one.

To create the a record you going to need an IP address, it can be something random like the below, or you can use http://icanhazip.com to get your actual current IP. Again to create a record, you can use the rackspace GUI (It’s under “Hosting” -> “Cloud Servers” -> “serverabc” -> “DNS” -> “yourdomain” > “Add”) or you can use rsdns….

[LINICKX@SERVER rsdns]$./rsdns-a.sh -n dynamichost.linickx.com -i 123.123.123.123 -t 3600

In the above the TTL is set to 1hr, this is so that DNS caches do not keep the record too long. That’s all the pre-work done, now lets get your dynamic host setup!

The script to update your a record is rsdns-dc.sh, and you run it like this…

[LINICKX@SERVER rsdns]$./rsdns-dc.sh -n dynamichost.linickx.com

Easy huh? The script uses icanhazip to get your current IP, it then update the A record with it.

I never switch off my router so I have create a created a cronjob to run that script every 2 hours, plus the 1hr TTL should mean that the record is roughly in sync with my IP without making unnecessary requests – You can run the script more often if you like, just stay under the limits –> according to the API guidelines you can make upto 25 changes per min / 2 per second.

I use redhat based linux systems, so I can simply drop the following file called rsdns-dc into /etc/cron.d/ with this…

* */2  * * *     linickx /home/linickx/bin/rsdns/rsdns-dc.sh -n dynamichost.linickx.com &>/dev/null

Now we are actually done! Free private Dynamic DNS on your own zone, what more could you want?

In my frustration I have given up and created a shell script which converts a CSV into an ASA output, simply create a two column CSV with Col A containing your starting IP and Col B containing you end IP.

The script is a recursive loop so should support large outputs such as 10.1.2.10 to 10.2.1.20 howvere I’m not actually sure you’d want that in your firewall config but I wrote the computability for the fun it!

Have fun, click “more” below if you can’t see the script!

#!/bin/bash

# Commas separated VAR....
IFS=","
while read name firstip lastip
# Loop around CSV
do

# Split up our first ip into it's octects
firstipfirstoctect=$(echo $firstip | awk -F "." '{print $1}')
firstipsecondoctect=$(echo $firstip | awk -F "." '{print $2}')
firstipthirdoctect=$(echo $firstip | awk -F "." '{print $3}')
firstipforthoctect=$(echo $firstip | awk -F "." '{print $4}')

# Split up our last IP into it's ocects
lastipfirstoctect=$(echo $lastip | awk -F "." '{print $1}')
lastipsecondoctect=$(echo $lastip | awk -F "." '{print $2}')
lastipthirdoctect=$(echo $lastip | awk -F "." '{print $3}')
lastipforthoctect=$(echo $lastip | awk -F "." '{print $4}')

	# Re-set BASH
	unset IFS 

	# Echo out the object GROUP name
	echo "object-group network $name"

	# Loop through 1st Octect
	for a in `seq $firstipfirstoctect $lastipfirstoctect`;
	do
		# test to see if we need to print the whole range
		if [ $firstipfirstoctect -lt $lastipfirstoctect ]
		then
			firstipsecondoctectCOUNTER="0"
			lastipsecondoctectCOUNTER="255"
		fi

		# first IP might not be 1
		if [ $a -eq $firstipfirstoctect ]
		then
			firstipsecondoctectCOUNTER=$firstipsecondoctect
		fi

		# last IP might not be 255
		if [ $a -eq $lastipfirstoctect ]
		then
			lastipsecondoctectCOUNTER=$lastipsecondoctect
		fi

			# Loop through 2nd Octect
			for b in `seq $firstipsecondoctect $lastipsecondoctect`;
			do

				# Same tests as before except, next octect.
				if [ $firstipsecondoctect -lt $lastipsecondoctect ]
				then
					firstipthirdoctectCOUNTER="0"
					lastipthirdoctectCOUNTER="255"
				fi

				if [ $b -eq $firstipsecondoctect ]
				then
					firstipthirdoctectCOUNTER=$firstipthirdoctect
				fi

				if [ $b -eq $lastipsecondoctect ]
				then
					lastipthirdoctectCOUNTER=$lastipthirdoctect
				fi

					# Loop through 3rd Octect
					for c in `seq $firstipthirdoctectCOUNTER $lastipthirdoctectCOUNTER`;
					do

						# copy / paste / tweak
						if [ $firstipthirdoctect -lt $lastipthirdoctect ]
						then
							firstipforthoctectCOUNTER="0"
							lastipforthoctectCOUNTER="255"
						fi

						if [ $c -eq $firstipthirdoctect ]
						then
							firstipforthoctectCOUNTER=$firstipforthoctect
						fi

						if [ $c -eq $lastipthirdoctect ]
						then
							lastipforthoctectCOUNTER=$lastipforthoctect
						fi

							# final octect... echo result.
							for d in `seq $firstipforthoctectCOUNTER $lastipforthoctectCOUNTER`;
							do
								echo " network-object $a.$b.$c.$d  255.255.255.255"
							done

					done
			done
	done

done<./FirewallRanges.csv

I use my shell all the time to ping stuff, renice processes and you know, whatever (like in the image below)…..

… having my todo list right there in front of me has been really helpful (The numbers in the square brackets!). Steve’s website suggests a quick update to your shell profile to add your task list to your prompt but I found running a python script each time I do anything quite slow, especially since I have two lists.

Below is my bash .profile file, there you can see the rather OTT change(s) I’ve made to integrate my todo lists into my shell prompt. I have two lists (work & personal) the number of things to do shown in my shell prompt gets updated each time the lists change (thanks to md5)…. and I hide my work list over the weekend

alias p='python ~/bin/t/t.py --task-dir ~/Dropbox/Tasks --list personal.tasks --delete-if-empty'
alias w='python ~/bin/t/t.py --task-dir ~/Dropbox/Tasks --list work.tasks --delete-if-empty'

function nick_PS1 {

        if [ -e "/Users/nick/Dropbox/Tasks/Personal.tasks" ]
        then
                CurrentPersonalMD5=`md5 ~/Dropbox/Tasks/Personal.tasks | awk '{print $4}' | cat `

                if [ -e "~/.tasks.personal.md5" ]
                then
                        LastPersonalMD5=`cat ~/.tasks.personal.md5`
                fi

                if [ "$CurrentPersonalMD5" == "$LastPersonalMD5" ]
                then
                        if [ -e "~/.tasks.personal.no" ]
                        then
                                NumOfPersonal=`cat ~/.tasks.personal.no`
                        fi
                else
                        NumOfPersonal=`p | wc -l | sed -e's/ *//'`
                        echo $NumOfPersonal > ~/.tasks.personal.no
                        echo $CurrentPersonalMD5 > ~/.tasks.personal.md5
                fi

                if [ $NumOfPersonal -ne 0 ]
                then
                        LEFT='['
                        RIGHT=']'
                        Personal="p:$NumOfPersonal"
                fi

        else
                NumOfPersonal=0
        fi

DayOfWeek=`date "+%u"`
if [ $DayOfWeek -lt 6 ]
then
        if [ -e "/Users/nick/Dropbox/Tasks/Work.tasks" ]
        then
                CurrentWorkMD5=`md5 ~/Dropbox/Tasks/Work.tasks | awk '{print $4}'`

                if [ -e "~/.tasks.work.md5" ]
        then
                LastWorkMD5=`cat ~/.tasks.work.md5`
        fi

                if [ "$CurrentWorkMD5" == "$LastWorkMD5" ]
        then
                        if [ -e "~/.tasks.work.no" ]
                        then
                                NumOfWork=`cat ~/.tasks.work.no`
                        fi
                else
                                        NumOfWork=`w | wc -l | sed -e's/ *//'`
                                        echo $NumOfWork > ~/.tasks.work.no
                                        echo $CurrentWorkMD5 > ~/.tasks.work.md5
                fi

                if [ $NumOfWork -ne 0 ]
                then
                        LEFT='['
                        RIGHT=']'
                        Work="w:$NumOfWork"
                fi

        else
                NumOfWork=0
        fi
else
 NumOfWork=0
fi

        if [ $NumOfPersonal -ne 0 ]
        then
                if [ $NumOfWork -ne 0 ]
                then
                        SEP="|"
                fi
         fi

        RESULT="$LEFT$Personal$SEP$Work$RIGHT"

        if [ -z $RESULT ]
        then
                RESULT="linickx@macbookpro"
        fi

        echo $RESULT
}

export PS1="\$(nick_PS1) \W \$"

… I think my next stop will be using geektool show the list/reminders on my desktop.

The advantage of doing this is that your host machine stays snappy, responsive and won’t get too over-loaded by jobs on your VMs!

#!/bin/bash
ps -xo pid,command | grep -v grep | grep startvm | while read line ;
do
        procID=`echo $line | awk '{print $1}'`
        sudo renice +10 -p $procID
done

The above code works on a mac; although I haven’t tested it, I recon to get it running on Linux you need to update the PS command, by swapping the x for an e… like this….

#!/bin/bash
ps -eo pid,command | grep -v grep | grep startvm | while read line ;
do
        procID=`echo $line | awk '{print $1}'`
        sudo renice +10 -p $procID
done

Have fun, suggestions and improvements welcome.

Recently I’ve been having a small problem with mediatomb, further investigation lead me to a “Inotify thread caught exception” error which can be fixed by recursively resetting your file permissions.

What I have done to fix the issue is save the following code as /etc/cron.daily/fix_mt.sh and ‘jobs a gooden’

#!/bin/bash
# Load up your mediatomb directories...
MediaTombDirectories[0]="/home/me/Videos"
MediaTombDirectories[1]="/home/me/Music"
# add more if needbe
# MediaTombDirectories[2]="/home/me/files"

# Setup find correctly.
export IFS=$'\n'

# Loop through our array.
for x in ${MediaTombDirectories[@]}
	do
		# Find all directories & subdirectories
		for i in $(find $x -type d)
			do
				# Fix Permissions
				chmod -c 775 $i
				chown -c me:user $i
			done

		# Find all Files
		for i in $(find $x -type f)
			do
				# Fix Permissions
				chmod -c 664 $i
				chown -c me:user $i
			done
	done

Quick tip: You (or root) will get e-mailed every time this executes, you can make the script more verbos by changing all “-c” to “-v“, or make it silent by removing the “-c” altogether.

Enjoy!

$ history | awk '{a[$2]++}END{for(i in a){print a[i] " " i}}' | sort -rn | head
114 ping
107 sudo
82 ssh
71 top
71 cd
68 iwconfig
56 ls
46 usbkey.sh
43 ps
33 evolution

The output shows what commands you type the most, usbkey.sh is a script to unlock the secret-keys held on my usb key-fob, sudo is high up probably cause I use sudo to bounce services (the intel wireless drive crashes quite alot and both it and Network Manager then need restarting) and evolution needs a shutdown every now and again The other commands are fairly self-explanatory.

So what’s your history?


#!/bin/bash
export IFS=$'\n'
for i in $(find $1 -type f)
do
echo "$i"
done