Geek(Wisdom).com - Systems Administration

Solution for umount "device is busy" errors

geekwisdom — Wed, 10 Jun 2009 16:04:10 +0000

We've all experienced it. We want to unmount something and the device is busy. Enter the lazy switch for the umount command.
umount -l /dev/
As soon as the last process stops using the device it gets unmounted. Many times this happens instantly.

Firefox 3 sec_error_crl_invalid errors

geekwisdom — Mon, 11 May 2009 06:13:59 +0000

For the last month or so I've been experiencing sec_error_crl_invalid errors on a couple of sites when using Firefox 3. Thanks to this post on NZGeek's blog I was able to resolve the issue. It turns out by deleting the CRLs (that where disabled anyway) I was able to solve my issue.

HOWTO: Apache Name-based SSL-enabled Virtual Hosting

geekwisdom — Thu, 26 Mar 2009 14:34:53 +0000

I want to do virtual hosting of SSL-enabled virtual hosts on the same Apache server as my other non-SSL-enabled virtual hosts. I don't want to assign more than one IP address to the server and all of my virtual hosts will be within the same domain (e.g., example.com).

BACKGROUND

When Apache processes a request for a name-based virtual host it receives the request from the browser, which includes the Host header (e.g., Host: www.example.com). Apache uses the Host header to determine which name-based virtual host to route the request to. It works this way regardless of the connection type, HTTP or HTTPS.

Automated backups of MySQL databases

geekwisdom — Fri, 06 Mar 2009 20:35:02 +0000

Unless you have intelligent backup software that can do something smart to backup your databases, restoring a backup of a running MySQL server is like restarting your database after a hard system crash, it's a crap shoot. Since I don't have any fancy backup software that can help I decided to use mysqldump to create a snapshot of my database server and write it out to a compressed SQL file. Then my (dumb) backup software can continue to be used and I will be able to recover easily if my server dies.

Here's the quick and dirty script:



#!/bin/sh

#

# This script automates a call to mysqldump

# and sends the output to a file in a backup

# directory. The script is set up to keep

# seven days of history.

#

# Before you can run this script you must

# set up a MySQL user that can perform the

# backup. This user must have permission to

# SELECT and LOCK TABLES. The user should not

# be permitted to access MySQL in any way other

# than through the local socket. Here's how the

# user should be created:

#

# GRANT SELECT,LOCK TABLES ON *.* TO 'SomeUser'@'localhost' IDENTIFIED BY 'SomePassword'

# FLUSH PRIVILEGES;

#

# This script should be owned by root and only

# root should be able to read, write, and

# execute it. (i.e., chmod 700)

#

Upgrading MySQL from version 3.23 to 5.0.x

geekwisdom — Wed, 04 Mar 2009 19:46:20 +0000

I recently had to upgrade a moldy old MySQL database server from version 3.23 to 5.0.x. Instead of stepping from 3.23 to 4.0, then from 4.0 to 4.1, and finally from 4.1 to 5.0.x I decided to use mysqldump.

I ran the following command on the old database server:
/path/to/mysqldump -u root -p -h oldserver.example.com --opt --all-databases > bigdump.sql

Then all I had to do was move the bigdump.sql file over to the new server and run the following command:
/path/to/mysql -u root -p -h newserver.example.com < bigdump.sql

Now all that is necessary is to flush the privileges so that users can access the databases. I logged into MySQL:
/path/to/mysql -u root -p -h newserver.example.com mysql

Extracting distinct e-mails from a large text file

geekwisdom — Fri, 05 Sep 2008 18:51:10 +0000

perl -wne'while(/[\w\.\-]+@[\w\.\-]+\w+/g){print "$&\n"}' BigFileContainingEmails.txt | sort -u > output.txt

Check out my awesome video tutorials!

wartex8 — Mon, 12 May 2008 20:07:37 +0000

I currently make how-to videos on computer related topics. Check out my videos at either
Youtube or Revver

/bin/rm: Argument list too long

geekwisdom — Thu, 06 Dec 2007 15:44:58 +0000

Do this instead: find . -name '*' | xargs rm

High Availability Web Services Using HAProxy

geekwisdom — Thu, 09 Nov 2006 19:36:23 +0000

I was recently tasked with increasing the up time of my employer's main Web site. The site uses a content management system that lives on two Windows/IIS servers. (I know, the system was purchased before I was hired.) One server is for making changes to content (design-time server) and the other is the public web site (run-time server). The design-time server has a complete copy of the site which is replicated to the run-time server. Unfortunately the run-time server has a habit of refusing to serve pages at the most inopportune times, usually when I'm on vacation or somewhere without a computer.

Butt Kicking Chair

geekwisdom — Thu, 27 Jul 2006 13:23:28 +0000

A couple of years ago I was sitting in one of those mind numbing meetings about stupid users or some such thing when I began to doodle and hit upon an idea. Wouldn't it be cool if all of our users sat in specially designed (or retrofitted) chairs that were capable of producing a shot to the sitter's posterior. The idea called for a chair, a boot, a lever, an actuator, a small computer with a network connection (wired or wireless), and some custom software. The computer would provide a network interface that would allow an administrator or help desk person to send a request to the chair and the person sitting in it would get a single kick in the pants. The idea for the interface later morphed into a web page and/or XML-RPC interface that listened to requests from authorized administrators which would trigger the butt kicking as well as various presets (single kick, small whooping, smack down, death by boot, etc).