Installing Debian Linux on Xen error INVALID_SOURCE – unable to access a required file in the specified repository

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I am working on a new virtualization implementation based on XEN Cloud Platform (XCP). After installing first XCP based hypervisor I tried installing a Debian 6 Linux OS with “New VM” option that later failed with an error:

INVALID_SOURCE – unable to access a required file in the specified repository: file://tmp/cdrom-repo–XXXXX/install.amd/xe/vmlinuz.

After a while, I figured out where was the problem – Debian doesn’t have vmlinuz so you shouldn’t select a Debian template from the drop down list, but rather select “Other install media” and install Debian from an ISO DVD image.… Read the rest of this entry »


Ripe today will start allocating IPv4 IPs from the last /8 block

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IPv4 are running out for all the regional registries and today Ripe NCC will probably start allocated IPv4 requests from the last /8 pool. This means no more PI space can be allocated and new LIRs will be assigned only 1024 IPs, not 2048 IPs as it used to be. See the daily allocated graph yourself:

http://www.ripe.net/internet-coordination/ipv4-exhaustion/ipv4-available-pool-graph

Welcome to the IPv6 world my friends!… Read the rest of this entry »


Protect .svn folders on Apache or Nginx web servers

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Sometimes I use subversion (svn) to publish my latest web sources to web servers and it’s always good to secure your .svn folders on the web server. You can easily do it for an Apache and nginx web servers.

I have published quick config examples below – feel free to use!

Apache config httpd.conf:

<DirectoryMatch .*\.svn/.*>
Deny From All
</DirectoryMatch>

Nginx config nginx.conf:

location ~ /.svn/ {
deny all;
}

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Sorry but the board is temporarily unavailable, please try again in a few minutes. phpbb error

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If you have noticed the following error after installing new phpbb forum:

Sorry but the board is temporarily unavailable, please try again in a few minutes

You may want to login into Administrator panel and go to General Tab -Load settings and change value of Limit sessions from 1 to 0 (unlimited).… Read the rest of this entry »


Enable Firefox full URL display

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New Firefox versions effectively hide full URL and when you copy the URL it adds http:// or https:// automatically (which is annoying), but it doesn’t show up URL bar by default.

To change it, enter the following in URL location and hit Enter:

about:config

Then find the following value:

browser.urlbar.trimURLs

and Toggle it to False.
This is it, now Firefox will display full URL in a location (URL) bar.… Read the rest of this entry »


MySQL Cluster 7.3 supports foreign keys

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Finally, MySQL Cluster 7.3 (not production version thought) supports foreign keys and that’s the feature many folks requested for years. With 7.3 you can drop and add foreign keys in real time – mysql cluster will deliver read/write requests online.

Check out Mysql labs and download MySQL Cluster 7.3 to test out new features and remember that MySQL Cluster 7.3 is not production stable version yet.… Read the rest of this entry »


Knot DNS server installation problem configure: error: liburcu not found

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I wanted to test out high-performance Knot DNS server and had problem while installing it on Centos 6.2 64-bit platform. The installation died with the error:

configure: error: liburcu not found

After some minutes of research, I found userspace urcu packages available for downloads at:

http://lttng.org/urcu/

Debian and Ubuntu Linux distributions does have these packages in their repositories.… Read the rest of this entry »


Time is running out for IPv4 addresses – get PI space while you still can

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Ripe will soon stop assigning PI IPv4 address blocks so you should act fast. You can get an IPv4 /24 PI space for multihoming purpose from Ripe and comply with their allocation policies if you need this space for multihoming.

Ps. This is my first blog post from Android phone!… Read the rest of this entry »


set_real_ip_from and real_ip_header settings for Nginx

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A few weeks ago we got a customer with multiple remote proxy servers accelerating customer’s web site for caching and performance issues. As always, I use Nginx as a front end and forwarding all dynamic queries (PHP) to back-end Apache/PHP for processing. And we hit the wall with getting the real client IP and pass it to the back-end Apache so that all posts and comments do show real client IP address. Hey, site admin requires blocking spamming IP blocks as well as flooders!

Front end proxy servers were already set-up to send X-Forwarded-For header with real client IP address.… Read the rest of this entry »


Memcached replication for data redundancy

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A lot of high performance web sites use memcached to speed up caching and serve content much faster to the web visitors. By default memcached doesn’t offer any data redundancy and no replication feature – memcached uses server RAM to store all data and if the server hardware fails or it is rebooted all data that’s stored in the memcached daemon will be lost. In order to increase memcached data redundancy and offer high availability you should check out RepCached (Web site: http://repcached.lab.klab.org/ ) – it offers multi-master and asynchronous replication for 1.2.x memcached versions.

You can use Layer-4 load … Read the rest of this entry »