Category: Server

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How to limit cpu usage for a process with cpulimit (Ubuntu / Debian server)

cpulimit is a tool that can be used to limit cpu usage (throttle cpu usage) for a single process (by its PID). cpulimit is useful to ensure that a single process would not hogs the cpu cycles, which can be use by other processes. cpulimit is different from ‘nice’ as it limits the real cpu usage for a process, while ‘nice’ controls scheduling priorities for a particular process.

How to use cpulimit?
Basic usage:
[bash]
cpulimit -p [pid] -l [ cpu percentage]
cpulimit -p 12345 -l 25
[/bash]

Running cpulimit on background:

[bash]
cpulimit -p 12345 -l 25 -z -b
[/bash]

Note: The cpu percentage is the same one as reported by the ‘top’ command.

cpulimit can be installed from Ubuntu and Debian 6.0 (Squeeze) repository through apt-get. The official website of cpulimit is http://limitcpu.sf.net

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Pingness.com: Free service to monitor website uptime

It is undeniable that uptime is important for business and personal websites. For example, a website with low uptime may mean that the host is having technical problem or the web server is overwhelmed by client requests (serving web pages may incur a lot of overhead)

Pingness.com service does not require sign-up, you need to submit your email address and website url, and pingness will send reports of your site downtime (if any) and when the website is back-online.

pingness
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lowendbox.com: A place to look for cheap-ish VPS and Dedicated Server – Less than USD7 / month!

lowendbox.com is a website that lists bare minimum VPS or Dedicated Server offerings with the lowest price.

For VPS, the category is divided by the virtualization technology and the operating system, as well as the geographical location of the data centers.

low end box VPS

Additionally lowendbox.com provides discussion forum for optimizing web server and databases for the bare minimum servers!

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How to save (or mirror) an entire website with httrack in Debian and Ubuntu

Httrack is a tool for copying and saving an entire website in Debian and Ubuntu. Httrack can crawl an online website save each of the pages (including graphic and other downloadable files).

Among httrack features are:

  • Able to continue interrupted downloads
  • Selective download
  • Customizable user-agent
  • Customizable Scan-rules, can exclude files from being crawled
  • Accept cookies
  • URL hacks
  • Tolerant requests support
httrack screenshot

Using ‘httrack‘ is easy, as it has built-in wizard that can guide you through the process of mirroring web sites. The user will be asked a series of question about the URL to be mirrored, the location where the files will be saved, proxy server and the user-agent to be used.

p/s: httrack perhaps is the only open-source website copier/downloader tool available for GNU/Linux operating system. It is efficient and easy to use. The only gripe that I’ve when using ‘httrack‘ is that it does not provide progress feedback (unlike its counterpart in Microsoft Windows) like ‘wget‘

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How to add contrib and non-free repository in Debian GNU/Linux

Debian GNU/Linux is probably the only Linux distro that has the largest software repository. However the default installation for Debian only includes the ‘main’ repository which is directly maintained by the Debian community and fulfills the Debian Free Software Guidelines (DFSG).

The two other repositories ‘contrib’ and ‘non-free’ are not enabled by default as it contains software that either does not meet DFSG requirements or depends on library or packages which does not meet DFSG requiments.

How to enable contrib and non-free repo in Debian
As ‘root’ you need to edit /etc/apt/sources.lst

Then add ‘contrib’ and ‘non free’ at the end of each line that begins with “deb” and “deb-src” just like the example:


deb http://http.us.debian.org/debian jessie main contrib non-free

deb http://security.debian.org jessie/updates main contrib non-free

Save the file, and run ‘apt-get update‘ and optionally ‘apt-get upgrade‘ to activate the changes.

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