Add ssh key to remote host

If you are working on recent versions of the *nix OS like Fedora or Ubuntu then you would know about the commad ssh-copy-id. But if you land up using one of the older versions like Solaris or something where the command is not present, then probably you need a simpler solution to this. One of the simplest solution is with a lot of assumtions, simply copy the id_rsa file to remote server and hope it works. And here is  a script to do just that:

using `!#$’ to referance backward-word

Here is something that I found on the commandlinefu

cp /work/host/phone/ui/main.cpp !#$:s/host/target

Ah well…its very interesting and very useful.

Some explanation:

!# – means the current command (similar to !! being the last command)

$ – represents the last parameter

:s – is used for substitution.

Related articles

• CommandLineFu: Amazing Collection Of Command Line Gems [Linux & Mac] (makeuseof.com)
• Oh, the Iron-y (ftalphaville.ft.com)

Compare files excluding certain lines.

Quick tip, you can use any expression for the sed commands in the (). With this trick you can redirect the stdout of 2 commands to the diff command. This might become very useful, if you want to compare 2 files, excluding the first  line.

diff <(sed '1d' file) <(sed '1d' file2)

More interesting example is where the string ABC is converted to abc before comparing in the second file with the following command:

Cont: Get yourself some more conkyrc files.

Last time we got ourselves some conkyrc files from the ubuntu forums. But that scripts gets the files only from the First page of the thread. Lets extend this further and get the script to get all the conkyrc files.

There are some 1048 pages in the thread, I am showing pages 1 to 3 but you can change 3 to whatever number you want 🙂

count=0
for i in {1..3}
do
    >.test
    >conkyrc
	echo "Getting page $i"
	curl http://ubuntuforums.org/showthread.php?t=281865\&page=$i |\\
         sed -n '// d'|\
         sed 's##\n-----------------------------------\n\n\n#' \
         >conkyrc
	dos2unix conkyrc
	cp conkyrc .test
	while [ $(wc -l .test|sed 's/[^0-9]//g') != 0 ]
	do
		sed -n '1,/------------------------/ p' .test|sed '$d' >conkyrc.$count
		diff .test conkyrc.$count |sed 's/^<.//'|sed '1, /---------------------/ d;2d'>.test
		((count++))
	done
	echo "Files so far are : $count"
done

Related articles

• Get yourself some conkyrc files. (amit-agarwal.co.in)
• HTC-Like Clock / Weather Conky Configuration (putokaz.wordpress.com)
• Split and join file on Mac OSX Terminal (lezeng.wordpress.com)

Creating a chroot environment – the script.

Here is the script, very simple and effective 🙂

#!/bin/bash -
#===============================================================================
#
#          FILE:  mkchroot.sh
#
#         USAGE:  ./mkchroot.sh
#
#   DESCRIPTION:  Make a  chroot environ and cd to it
#
#       OPTIONS:  ---
#  REQUIREMENTS:  ---
#          BUGS:  ---
#         NOTES:  ---
#        AUTHOR: Amit Agarwal (aka), 
#       CREATED: 09/03/2011 02:53:37 PM IST
# Last modified: Sat Sep 03, 2011  03:11PM
#      REVISION:  ---
#===============================================================================

 binaries=( bash2 ls cat vi vim sudo)
#===  FUNCTION  ================================================================
#          NAME:  copy_binary
#   DESCRIPTION:  copy binary to chroot
#    PARAMETERS:
#       RETURNS:
#===============================================================================

copy_binary ()
{
   cmd=`which $1`
   echo $cmd
   cp $cmd bin/
   ldd $cmd
   while read line
   do
      while read ld
      do
         if [[ -f $ld ]]
         then
            echo copy $ld
            cp $ld lib/
            if [[ -L $ld ]]
            then
               ld1=$( ls -l $ld |sed 's/.*> //')
               echo "  copy $ld1"
               cp  /lib/$ld1 lib/
            fi
         fi
      done < <(echo $line|sed 's/.*> //'|sed 's/ .*//')
   done < <(ldd $cmd)
}	# ----------  end of function copy_binary  ----------

#===  FUNCTION  ================================================================
#          NAME:  init
#   DESCRIPTION:  Do the required initialization
#    PARAMETERS:
#       RETURNS:
#===============================================================================
init()
{
   mkdir -p {root,home,dev,etc,lib,usr,bin}
   mkdir -p usr/bin
   mkdir -p libexec/openssh



   mknod -m 666 dev/null c 1 3

   cd etc
   cp /etc/ld.so.cache .
   cp -avr /etc/ld.so.cache.d/ .
   cp -avr /etc/ld.so.conf.d/ .
   cp /etc/ld.so.conf .
   cp /etc/nsswitch.conf .
   cp /etc/passwd .
   cp /etc/group .
   cp /etc/hosts .
   cp /etc/resolv.conf .
   cd -
}
cd $1
if [[ -f .status ]]
then
   cat .status
   echo "Not running now"
else
   init
   for i in ${binaries[*]}
   do
       copy_binary $i
       cp -avr /etc/${i}* etc/
   done
   ln bin/bash2 bin/bash
   echo "complete" > .status
fi
cp -avr ~/bin/automation root/automation
sudo chroot .

.

Creating a chroot environment in Fedora with bash and other utils.

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I am testing some of my scripts to work on a very old system and there the versions of the most popular applications are very old, real old :(. So, some of things that I am very used to since last couple of years, do not seem to work as expected and I need to keep verifying a lot of things on the server, very inconvinient to keep testing the script on the server (need to connect on VPN) just to test some very simple things.

better bash debugging

I was trying to debug some bash scripts yesterday and learnt something new 😉
There are lot of things in bash that you can use to debug and to start with you can enable xtrace mode as follows:

set -x

With this set you will see that all the commands are printed along with all other information as they are executed.
This you can do for any line or for the function or for the whole script. Once you set the option you can turn it
off with