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."
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 Zombie Process. But these two are totally different from each other. An Orphan Process is nearly the same thing which we see in real world. Orphan means someone whose parents are dead. The same way Orphan process is a process, whose parents are dead, that means parents are either terminated, killed or exited but the child process is still alive.
Everyone is not as lucky as having a full fletched email client like thunderbird or kmail to send mails. There is one unlucky group known as system administrators who have to send the mails either through the command line or a script running on the remote server. Also, apart from sending the emails, sometimes one needs to test or debug the email server which can't be done by traditional email clients. If you are one of those system administrators and are scared, then you shouldn't be, because this is where netcat comes to rescue.
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.
