DNS stands for “Domain Name Service”. It is the mechanism in which the internet is able to map a name (eg www.sgasoftware.com) to an IP address (eg 12.34.56.78). This writeup is not designed to be 100% technically accurate. Rather, it is designed to give a layman understanding of relevant parts of the DNS system. Much more [...]
Archive for the ‘System Administration’ Category
Essentials of DNS: understand the basics well
Posted in Interesting, Perspective, System Administration, Technique, tagged Distibuted Systems, DNS, Internet, Network, Perspective, Technology on December 15, 2010 | Leave a Comment »
How to force-drop a postgresql database by killing off connection processes
Posted in Engineering, Linux, Open Source, Software, System Administration, Technique, tagged Drop Database, Kill Process, PostgreSQL, Process on November 3, 2010 | 4 Comments »
Ever need to drop a postgresql database, but it would not let you because there are open connections to it (from a webapp or whatever)? Quite annoying. If on a production server, and other databases are being used, restarting postgresql is a last resort, because it generates downtime for your site (even if small). I [...]
Ubuntu Post-Install tips…
Posted in Linux, Open Source, Software, System Administration, Technique, tagged Ubuntu, Ubuntu Partner Repositories, Ubuntu Setup on June 14, 2010 | Leave a Comment »
I received this from a friend, and thought I would post it here in case anyone would find it useful. After Installing Ubuntu, basically I do this: Go to: System -> Administration -> Software Sources -> Other Sofware, and enable partner repository. After that, we can this on a Terminal: sudo apt-get update sudo apt-get dist-upgrade sudo [...]
PostgreSQL Dump and Restore Notes
Posted in Open Source, Software, System Administration, Technique, tagged database backup, pg_dump, pg_restore, PostgreSQL on May 16, 2010 | Leave a Comment »
The pg_dump and pg_restore commands provide excellent flexibility in storing a compressed dump file, and selectively restoring any part of it. I’ve found that dropping and re-creating the target database is the cleanest way to restore a dumpfile — no stray relations left to cause trouble. Unless you own all of the objects being restored, [...]
nginx restart error
Posted in Linux, System Administration, Technique, tagged nginx, nginx configuration, nginx error on February 24, 2010 | Leave a Comment »
Was playing around with nginx on Centos 5 (EPEL package). Most of the time I ran: I would get this message in the /var/log/nginx/error.log file: After some hunting around, it appears to be a known bug in nginx (perhaps perl in nginx?)… Anyway, a simple workaround is to do this: Or, simply edit /etc/init.d/nginx, and [...]
Example Automated MySQL Backup Script
Posted in Linux, System Administration, Technique, tagged backup, Backup Script, MySQL, System Administration on December 26, 2009 | Leave a Comment »
Rather than use –all-databases, which will prevent you from being able to selectively restore any single database, consider the following: Ideally, you should have a daily backup, with some history. It should be bulletproof (–force), it should be logged (>> …log), it should be compressed (| gzip), it should keep separate copies of each database, [...]
Freeky Bug
Posted in AppCove, Engineering, Interesting, System Administration, tagged Fail Bug, Load Balancing on August 22, 2009 | Leave a Comment »
Ever have one of those bugs that customers complain about, but you just cannot reproduce it? Here is a good one… Customers were complaining about being logged out when clicking a download link. This particular setup is a Cisco CSS 11501 series load balancer with 2 Dell Poweredge web servers sitting behind it. Each webserver [...]
Interesting Thoughts on Cloud Server Performance
Posted in Engineering, Linux, System Administration, tagged AB, Apache, Benchmarking, Cloud Server, Performance on August 1, 2009 | 4 Comments »
Apache load testing on a Cloud Server – Jason – 7/31/2009 I recently created a cloud server for a wordpress blog, and configured it to the point that the blog was working OK. Then I decided to check the performance aspects of the server, as it was a small 256 MB + 10GB machine. Using [...]
Updating a cert on the Cisco 11500 Series Content Services Switches (CSS)
Posted in AppCove, Linux, System Administration, Technique, tagged Cisco CSS, SSL Certificates, System Administration on April 6, 2009 | Leave a Comment »
Upgrading a SSL certificate using the Cisco 11500 Series Content Services Switch (CSS)
I highly recommend yum + createrepo + rpmbuild
Posted in AppCove, Linux, System Administration, Technique, tagged Apache, EPEL, Linux, RHEL, RPM, System Administration, YUM on March 8, 2009 | Leave a Comment »
As I was discussing lightly before, I have recently been involved in building quite a few RPMs for our server clusters at AppCove. Where we have arrived: Our (new) primary production cluster consists of multiple RedHat Enterprise Linux 5 boxes in different capacities (webserver, appserver, database master, database slave, etc…). Each machine is registered with [...]
