Archive for 'Fedora'

Zombie Process

It's a pretty much common question asked in most of the interviews related to Linux, and most of the time people got it confused with Orphan Process. But these two are totally different from each other. A Zombie Process is nearly the same thing which we see in lot of horror movies. Like the dead people which don't have any life force left, Zombie processes are the dead processes sitting in the process table and doing nothing.

To explain this in much better way, "Zombie process or defunct process is a process that have completed the execution, have released all the resources (CPU, memory) but still had an entry in the process table."

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Upgrading the system is one of the very common tasks a Linux Administrator usually do. One can easily update the system with Yum or apt-get commands but the main problem which everyone faces is to reboot the system after a kernel upgrade. This comes out to be a big problem for small organizations, where one don't have High Availability setup and can't afford to reboot the system because of the upgrade.

Since reboots are disruptive, many system administrators delay the update of there patches and makes their system vulnerable to attacks. Below given is the frequency of reboots needed in the last year for respective flavors of linux.

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Configure Tata Photon Whiz On Ubuntu Linux

Tata indicom is offering unlimited surfing plus download at very affordable prices with their Tata Photon Whiz. Although it's at compromised speeds but still, it is unlimited. Configuring this card at windows is pretty much easy, as it is always with all other softwares. Within few clicks, your card will be working and you will be ready to browse net within sometime. but as always, configuring it on Ubuntu linux is not so easy but at the same time not so difficult too if you follow right steps. Below I will be explaining them.

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Q. How I should enforce users to change password at their first login ?

A. This is one of the very basic needs which shows up in most of the companies. As a system admin, I am sure this will be asked from you.

To setup this there are various ways, but I believe one of the very simplest one is the one I am going to explain below.

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Though this warning looks pretty much scary but the reason for this is very much simple and the solution as well.

Q. When did you get this error ?

A. The possible reasons for getting this error are:

  • You have re-installed you system and trying to ssh to the newly installed system.
  • You have assigned the IP address of one system to another system and trying to ssh.
  • You system is dual boot with different ssh keys in both flavors of linux.
  • You are using an IP for load balancing and trying to ssh to the same IP.
  • You generated new ssh keys for your system. (Read this article for the re-generation of the host keys: Generate SSH host keys)
  • Someone trying to do some nasty things, or you can say man-in-the-middle attack.

There could be lots of solution for this problem, which are explained below:

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