Command buffering control

Thu 31 December 2015 by admin

Debugging output from hping3 using grep via pipes doesn't show any result. It's because hping3 output is buffered, to make things working as you expect use tool called stdbuf from coreutils package in ubuntu and:

# stdbuf -oL hping3 -S -p 80 blog.witalis.net | grep <lookfor>

it means that each line is buffered not the whole stream. Imagine you can pass output buffered by line, so you can get live stats like in this ping example:

$ ping <host> | stdbuf -oL cut -d'=' -f4 | stdbuf -oL awk '{split($1,a,"."); print a[1]}'  | xargs -L 5 | stdbuf -oL sed 's/ /\n/g' | uniq -c

you are only interested in response time, you measure uniq count values in 5 probes at once.


Distributed Docker Stats

Mon 21 December 2015 by admin

Initial commit for project that helps to make: docker stats command more distributed:

https://github.com/witalisoft/dds

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Journald - log rate limiting

Tue 03 November 2015 by admin

It seems to be an easy task, make available logging from haproxy to syslog. Configuration on haproxy side was pretty easy, log file start growing, but from time to time there were some pauses. Rsyslog was the first victim, I dig into limiting configuration area, but default limits doesn't ...

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InfoMarquee

Sat 10 October 2015 by admin

After one year break I'm back. This time with new ideas more concentrating on dev side of sysadmin. The first new project called infomarquee published on github. Project brings user defined alerts in TV news station style. First iteration consist of two headlines with user defined alerts with duration ...

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How domains are being resolved ?

Thu 23 October 2014 by admin

Not so far ago I was doing some cleanup work with static entries in /etc/hosts. I was wondering how many of these static entries are being actively used. To figure out I started digging, but without much luck. Tools like strace, ltrace doesnt give me a clear look which ...

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How safely change ip address on remote host ?

Sun 05 October 2014 by admin

Routine task change ip address on remote host without cut off. There are a lot of possibilites i.e. from reboot with new ip address to some fancy stuff with cron job. But there is a one method to make it clear and elegant.

Simply set:

echo 1 > /proc/sys ...
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New look and feel

Sun 29 June 2014 by admin

After couple months of inactivity I am starting with new look of blog site. It's not only a new theme, but it's completly rewrite engine. No more complexity of Wordpress on top of Varnish,Nginx,PHP,MySQL just pure static content generated by Pelican. Static website is served ...

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Jesień Linuksowa 2013

Tue 08 October 2013 by admin

Tym razem po drugiej stronie mikrofonu:

Zaopiekuj się moimi logami
Witold Duranek

więcej na: http://jesien.org/2013/pl/agenda

Zapraszam,

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Zerofree your filesystem

Sat 28 September 2013 by admin

Lets assume that you have file image:

dd if=/dev/zero of=file.1 bs=4k count=128

on top of it you create filesystem ext3/ext4

mkfs.ext4 /root/file.1

mount it, create remove some files etc. and you gonna make it more space efficient, that's why ...

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Some notes about memory ballooning in VMware

Sun 01 September 2013 by admin

Couple days ago I found out that memory usage grow rapidly on one server. After couple minutes of investigation, it was clear that memory balloon take place. Of course it will happen only if you have vmware tools installed. To find out what was happening, you can look at vmware ...

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