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Recently I started to play with scapy - a powerful interactive packet manipulation and custom packet generation program written using Python. Please note that this tool is not for a new Linux / UNIX users. This tool requires extensive knowledge of network protocols, packets, layers and other hardcore networking concepts. This tool is extermly useful for
a] Understanding network headers
b] Testing network security
c] Write your own utilities using scapy
d] Decoding protocols etc

From the man page:

You can use this tool to check the security of your own network as it allows to forge or decode packets of a wide number of protocols, send them on the wire, capture them, match requests and replies, and much more. It can easily handle most classical tasks like scanning, tracerouting, probing, unit tests, attacks or network discovery. It also performs very well at a lot of other specific tasks that most other tools can't handle, like sending invalid frames, injecting your own 802.11 frames, combining technics such as VLAN hopping+ARP cache poisoning, VOIP decoding on WEP encrypted channel, etc.

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You can use "type" or "whereis" command to find out which command shell executes and to print binary (command) file location for specified command.

whereis command example

Display ls command location along with man page path:
whereis ls
Output:
ls: /bin/ls /usr/share/man/man1p/ls.1p.gz /usr/share/man/man1/ls.1.gz

type command example

Find out which command the shell executes:
type -a ls
Output:
ls is aliased to `ls --color=tty'
ls is /bin/ls

Related: How Linux or UNIX Understand which program to run - PART I and How BASH Shell Command Search Sequence Works

When you work in tech support department and deal with inexperienced clients debugging problems turns into a nightmare. As a sysadmin, you won't become too paranoid if less experienced people have root-access. As a consultant, you won’t feel isolated if you don’t have remote access to your systems. As a support engineer, you won’t become frustrated if a customer has fiddled around with some important config file and you have to find which. As a performance tuner, you can capture the state of the system configuration in between performance tests/benchmarks.

Luckily, some nifty tools can create a system's hardware and software configuration snapshot. This kind of information is valuable asset while troubleshooting problems.

dconf (System config collector) is one of such tool. It allows to take your system configuration with you on the road, compare identical systems (like nodes in a cluster) to troubleshoot HW or SW problems, indeed a lifesaver.

Dconf is also useful in projects where you have to manage changes as a team. Dconf can run periodically and send out system changes to a list of email addresses so that they can be revised and discussed in group.

You can customize your dconf configuration for specific needs, like making a profile of your web server’s hardware or copy specific software configuration files to send out or compare with other systems.

As a sysadmin, you will not become too paranoid if less experienced people have root-access. As a consultant, you will not feel isolated if you do not have remote access to your systems. As a support engineer, you will not become frustrated if a customer has fiddled around with some important config file and you have to find which. As a performance tuner, you can capture the state of the system configuration in between performance tests/benchmarks.

Install dconf

If you are using Debian / Ubuntu Linux then type the command:
# apt-get install dconf
You can download Dconf for RedHat or Suse Linux here

Create a system's hardware and software configuration snapshot

Once installed you can simply create a snapshot using dconf command:
# dconf
It will write snapshot in /var/log/dconf/ directory. To view current snapshot info, enter:
# zcat /var/log/dconf/dconf-$HOSTNAME-latest.log.gz
To check the latest changes against the previous snapshot:
# zdiff -u /var/log/dconf/dconf-$HOSTNAME-previous.log.gz /var/log/dconf/dconf-$HOSTNAME-latest.log.gz

See also:

I am responsible for couple of MS-Windows servers and Windows XP/Vista/7 workstations too. When I work from home, I need a way to get into Windows XP/2000/Vista/2003/2008/7/Vista operating systems for work.
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How do I Print Out a Linux man or info Page?

Some time it is necessary to print a Linux man or info page. To print a ls command man page type the following command:
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