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.

faster bash operations on files with File Descriptors.

I was writing a bash script that would do some operations and read and write to file. Seems that that was pretty simple with

  <td>
    <div class="text codecolorer">
      while read line<br /> <br /> do<br /> <br /> done<file
    </div>
  </td>
</tr>

and then use redirection operations like “>” and “»” to write to file. Done with the script pretty fast. So far so good, when I went for real life tests, no one was interested in using it, why? Simple, it was simply taking too long. The file was reading about 10K lines and writing about 50 lines and was taking about more than 10 minutes.

Terminating a SSH session after starting background process.

This is too good. If you are planning to start a background process in the bash script in the background and continue in the script, you cannot do it until…….

You would need to close the stdout/stdin and stderr before you can terminate any ssh session automatically. Here’s some more light on this topic.

http://lists.debian.org/debian-user/2005/09/msg00254.html

On Thu, Sep 01, 2005 at 05:33:28PM -0400, Roberto C. Sanchez wrote: > I occasionally log into a machine remotely and start a process in the > background: > > command & > > However, when I log out of the machine, the ssh process on my local > machine blocks. I guess that it is becuase the remote still has jobs > running. Is there a way to get it start the process in the background > and then detach from the shell? I have already tried this:

browsing the windows machines and their shares – listing

smbtree is a very nice command to check all the machines that are present in the LAN (your connected network). For this to work you may need to look at this article also.

  <td>
    <div class="text codecolorer">
      smbtree -U <strong>username
    </div>
  </td>
</tr>

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client lanman auth is disabled error for samba

The error:

Server requested LANMAN password (share-level security) but ‘client lanman auth’ is disabled

is easily fixable. You just need to tell samba that client lanman auth is enabled. And here is how to do this:

If you are getting this error then add the following in the globals section of the samba configuration:

client lanman auth = Yes

Ensure that you change this in the file /etc/samba/smb.conf

10 Useful Sar (Sysstat) Examples for UNIX / Linux Performance Monitoring

10 Useful Sar (Sysstat) Examples for UNIX / Linux Performance Monitoring

by Ramesh Natarajan on March 29, 2011

Using sar you can monitor performance of various Linux subsystems (CPU, Memory, I/O..) in real time.

Using sar, you can also collect all performance data on an on-going basis, store them, and do historical analysis to identify bottlenecks.

Sar is part of the sysstat package.

This article explains how to install and configure sysstat package (which contains sar utility) and explains how to monitor the following Linux performance statistics using sar.