RAM plays an important role in the performance of a system. So we should monitor this memory usage to troubleshoot system. free is the basic command to get details of RAM and swap usage. #freeExample :# free total used free shared buffers cachedMem: 3059872 2842016 217856 0 33936 2012684-/+ buffers/cache: 795396 2264476Swap: 2000052 67672 1932380 When you see it’s giving total size, used and free size in bytes. If you want to see in MB specify -m option in free #free -mExample :# free -m total used free shared buffers cachedMem: 2988 2784 203 0 33 1974-/+ buffers/cache: 776 2211Swap: 1953 66 1887 Any other commands to check RAM?The answer for this is yes.1. Use proc file system to get detailed RAM usage of the system. #cat /proc/meminfo2. Use top command to see RAM usage So with top too you can see RAM usage live. Please visit http://www.linuxnix.com for more linux admin...Read More
Month: May 2010
What is a”Core file” ? Ans : A core file is created when a program is crashed/stoped abnormally due to some bug. This will be huge size which contains all the memory info, crash info which is used for programmers to debug the issue and find a solution or patch to that bug. Why we system administrators are interested in that core files?Ans : This is because of their size. As we do monitoring of systems on daily basis but suddenly your disk is full one day when you came to office, you are total blank thinking how come disk is full though there is no much user activity etc. So core files are one reason which will eat up our disk. Which you have to check for when sudden disk activity is observed. How to find core files ? #find / -name core This find command will search entire filesystem for core files.. once you find them use rm command to remove those files..#rm -rf core So how it got it’s name?A core dump file gets it’s name from an old memory technology using tiny magnetic cores for storage. Please visit http://www.linuxnix.com for more linux admin...Read More
A "defunct" processes is also known as a "zombie" processes. A Zombie process is referred as dead process which is receding on your system though it’s completed executing. In one shot we can say it’s a dead processes which is still in RAM. This process will be in your process table and consuming your memory. Having more defunct process will consume your memory which intern slows your system. We have to kill the defunct process in order to free RAM and make system stable. Why defunct process are created? Ans : When ever a process ends all the memory used by that process are cleared and assigned to new process but due to programming errors/bugs some processes are still left in process table. These are created when there is no proper communication between parent process and child process. Some FAQ? 1. How to find a defunct process? And : Grep defunct value in ps -ef output #ps -ef | grep defunct 2. How can I kill a defunct process? And : Just use kill command #kill defunct-pid 3. Still not able to kill? Ans : Then use kill -9 to force kill that process #kill -9 defunct-pid 4. Still have an issue in killing it? Ans : Then try to kill it’s parent id and then defunct. #kill parent-id-of-defunct-pid Then #kill -9 parent-id-of-defunct-pid 5. Still having defunct? Ans : If...Read More
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Linux Bash History: Replace occurrences in last commandNov 20, 2016 | Basics
My name is Surendra Kumar Anne. I hail from Vijayawada which is cultural capital of south Indian state of Andhra Pradesh. I am a Linux evangelist who believes in Hard work, A down to earth person, Likes to share knowledge with others, Loves dogs, Likes photography. At present I work at Bank of America as Sr. Analyst Systems and Administration. You can contact me at surendra (@) linuxnix dot com.