LPP » HPC

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h1. Bash tricks

h2. Get disk usage

<pre><code class="bash">

df -h

</code></pre> 

Will give you something like this:

<pre>

Sys. de fichiers       Taille Utilisé Dispo Uti% Monté sur

/dev/sde1                110G    8,1G   97G   8% /

devtmpfs                 126G       0  126G   0% /dev

tmpfs                    126G       0  126G   0% /dev/shm

tmpfs                    126G    920K  126G   1% /run

tmpfs                    126G       0  126G   0% /sys/fs/cgroup

tmpfs                    126G    4,0K  126G   1% /tmp

/dev/mapper/ddf1_DATA2    15T    7,7G   14T   1% /home

</pre>

h2. Get CPU and RAM usage

<pre><code class="bash">

htop

</code></pre> 

Will give you something like this:

p=. !{width: 80%}htop.png(htop screenshot example)!

To get more information about htop see "here":http://htop.sourceforge.net/index.php?page=main

h2. Start a Job without a queue

All process started from ssh are terminated when you close the ssh connection, even if you fork them

(./app &). They are closed because when a process is closed the system send the SIGTERM signal

to all its children, it’s done to avoid zombies process on a machine. To keep your task alive when

you disconnect from ssh, you should use screen ("tutorial":http://www.rackaid.com/blog/linux-screen-tutorial-and-how-to/), it will block the SIGTERM signal. To

start your application with screen:

<pre><code class="bash">

screen # to start screen

./your_app   #to start your application or any other command

             #type ’ Ctrl-A’ d to leave screen with your application running in background

</code></pre> 

To reconnect to your previous session:

<pre><code class="bash">

screen -ls    # to list running sessions

screen -r 33287.pts-36.bender # to reconnect to 33287.pts-36.bender session

exit # to close your screen session

</code></pre>