Archivo del Autor: hvivani

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sysadmin, developer, RHCSA

task blocked for more than 120 seconds


When we run very stressful jobs on clustered environments, where IO activity is very high. It is pretty common to start seeing these messages on the ‘dmesg’ kernel output: [24169.372862] INFO: task kswapd1:1140 blocked for more than 120 seconds. [24169.375623] … Seguir leyendo

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failed to alloc buffer for rx queue


If we put enough pressure over the ENA network driver, we’ll start seeing these “failed to alloc buffer for rx queue” messages on the ‘dmesg‘ output. [56459.833033] ena 0000:00:05.0 eth0: failed to alloc buffer for rx queue 4 [56459.836477] ena … Seguir leyendo

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Count and Say


/*Lets write an algorithm that, given an initial value, will produce the next ‘count and say’ sequence: 1, 11, 21, 1211, 111221, 312211, 13112221, 1113213211, … */ public class CountAndSay{ public static void main(String[] args){ System.out.println(“Count and Say algorithm”); System.out.println(“next … Seguir leyendo

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Listen on a port/Send data to a port


Listening with nc: nc -l 8089 Checking that 8089 port is listening: netstat -nap|grep 8089 (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) tcp 0 … Seguir leyendo

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Move a Linux running process to a screen shell session


Use case: You just started a process (i.e. compile, copy, etc). You noticed it will take much longer than expected to finish. You cannot abort or risk the process to get aborted due to the current shell session finishing. It … Seguir leyendo

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Getting latest EMR release label


Usually latest release label gets updated on EMR’s Whats New page. So a way to getting the last EMR release label would be:   curl -s https://docs.aws.amazon.com/emr/latest/ReleaseGuide/emr-whatsnew.html |grep “(Latest)”|head -n1|awk ‘{ print $3 }’   Have fun!    

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Update protobuf to 2.5 on Centos 6


Update protobuf to 2.5 on Centos 6: $ cd /usr/local/src/ $ wget https://github.com/google/protobuf/releases/download/v2.5.0/protobuf-2.5.0.tar.gz $ tar xvf protobuf-2.5.0.tar.gz $ cd protobuf-2.5.0 $ ./autogen.sh $ ./configure –prefix=/usr $ make $ make install $ protoc –version Install protobuf for java $ cd java … Seguir leyendo

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