linux Archive

Zombie vs Orphan process

When a process terminates, its resources are deallocated by the operating system. However, its entry in the process table must remain there until the parent calls wait(), because the process table contains the process’s exit status. A process that has terminated, but whose parent has not yet called wait(), is known as a zombie process. All

Temporary failure resolving – sudo apt-get update in ubuntu

If you are trying to update ubuntu respository and getting error: W: Failed to fetch http://us.archive.ubuntu.com/ubuntu/dists/trusty-backports/Release.gpg  Temporary failure resolving ‘us.archive.ubuntu.com’ just check the DNS. Set the Google DNS (8.8.8.8) in /etc/resolvconf/resolv.conf.d/base [crayon-5c103d3053535532385643/] then [crayon-5c103d305354f315106090/] After this procedure, I was able to resolve hostnames and [crayon-5c103d3053568539010744/]

Bash script to get average time from logs

What if we have logs of a server like apache or syslog server and we want to get average time from timestamps of all rows. How can we do it? Basically, we need to filter timestamp (column-8) from each row and just find its average. Below is the screenshot of the problem. (click on the

Kill multiple pid with same process

Sometime back I caught up in a situation where I need to kill multiple pid invoked from same process. So, all process have same name Assume, process invoked for “vim” editor. If I have 20 “vim” process running and I want to kill all of them, what’s the best way to do it? #There are multiple ways:

TCPDUMP examples

Tcpdump is a command-line based packet capture tool like wireshark which is GUI. Capture all traffic on ethernet interface: $tcpdump –i eth0 2. Filter by host IP-address: $tcpdump host 10.0.2.15 3. Filter traffic by source and destination ip-address: TCPDUMP filter by source and destination:             $tcpdump src 10.0.2.15        

CURL command examples

CURL is a command line tool used to transfer and retrieve data in web. Let’s have a look at few of the useful options while debugging web issues. Basic syntax $CURL <Options> <hostname or ip-address> Options are optional. Hostname and IP-address can be interchanged depends upon the options we are selecting. First example is to use