By default the number of open files pro user in Ubuntu 8.04 is 1024. In my case this number was too small so I have to increase it.This is done with the ulimit command:
$ulimit -a # see all the kernel parameters
$ulimit -n #see the number of open files
$ulimit -n 9000 # set the number open files to 9000
The problem with this way is that the ulimit parameter is only set currently for this command terminal and user.If you open a new tab and type again ulimit -a you will see that the number of open files is 1024.This means that after a reboot you’ll need to set the parameter again.
First, in order to set this options automatically you have to edit the etc/security/limits.conf file.
$sudo gedit /etc/security/limits.conf #open the file in gedit
The # means that this part is commented.The wildcard * means for all users.We need to set the nofile option meaning maximum number of open files.If you want to change the number of files of user, you should add this line in the limits.conf:
user soft nofile 9000
user hard nofile 65000
If you want to set the nofile only for superuser you just write root instead of user.
root soft nofile 9000
root hard nofile 65000
Second you have to add a line in the /etc/pam.d/common-session file:
$ sudo gedit /etc/pam.d/common-session #open the file in gedit
Then add the line:
session required pam_limits.so
Now after rebooting you can see in the terminal with ulimit -a the change.
The option with wildcard *didn’t work for me , because I used root accout to run my programms and wildcard option doesn’t affect the superuser.
Remark: Using the same steps you should be able to set and change other parameters ( core file size, max user processes, stack size ….) from the ulimit options.
This week in my blogging news I see an interesting trend of accepting and realizing that the Virtualization is part of the Cloud Computing. I think this is no surprise as the term Cloud Computing is cited as something general and there are various definitions of it.The Cloud is kind of the main term which encapsulates various layers of abstractions ( existing technologies ) with the main goal to make big data centers ( systems ) easier to manage and use.So here is again a list of the most interesting links:
Virtualization as a term is something fairly new and most of the people are not really sure what’s the meaning of it.I will try to include some definitions and useful links in order to give a light for the people searching around.Wiki definition:
“[Virtualization is] a technique for hiding the physical characteristics of computing resources from the way in which other systems, applications, or end users interact with those resources. This includes making a single physical resource (such as a server, an operating system, an application, or storage device) appear to function as multiple logical resources; or it can include making multiple physical resources (such as storage devices or servers) appear as a single logical resource.”
That’s a nice presentation at DefCon 2007 given by D.J.Capelis attacking some of the problem issues in server virtualization and precisely concerning security.
Next comes the need of a fresh image with installed OS which can be found on Thoughtpolice.They have done great job compiling such a big list of open source operating systems:
ThoughtPolice VMware Images
VMware lets you run another computer in your computer. Try out another operating system, test a different platform, preview a new distro. Hopefully this page of VMware images, or “Virtual Appliances” is useful.
Get the free VMware Player (or VMware Server, ESX 3, or VMware Workstation)
Download the image you want to use (see the list below)
Load the image in VMware
All of these VMware images are straight installs of the distribution, with all the default options chosen. This means you will be using and American English with an American keyboard. No tinkering was done – this means that no security updates have been applied – so be careful! See the 1 minute HOWTO guide for instructions on changing the language and keyboard, and on applying security updates.
There is also a step-by-step walkthrough on how to create your own VMware image using VMware Workstation.
The torrent downloads here are VERY FAST, likely much, much faster than your net connection. If you want the image quickly, definitely use the torrent.
Get a BitTorrent downloader, like uTorrent (free!)
Click one of the fast torrent download! links below
There will be a short pause before, and then your high speed download will begin
CentOS 4.6, server install. Long Term Support (until 2012!) permalink