yum install php53-xml

or if you’re using puppet

package { ["php53-xml"]:
          ensure => present
        }

And finally, to get it to install, I used the below. I had to make it go to multiple lines to fit on the page but I have it all on 1 line in my puppet script:

exec { "pear channel-discover pear.phpunit.de;
pear channel-discover pear.symfony-project.com;
pear install --alldeps phpunit/PHPUnit  ":
          creates => "/usr/bin/phpunit"
 }

yum install -y gcc kernel-devel-`uname -r`
mkdir /mnt/cdrom
mount -o ro -t iso9660 /dev/cdrom /mnt/cdrom
sh /mnt/cdrom/VBoxLinuxAdditions-amd64.run

Info found on tuxtraining.com

Here’s an example:

~ jhaddad$ pwd
/Users/jhaddad
~ jhaddad$ ( cd /tmp/; touch bacon.txt )
~ jhaddad$ pwd
/Users/jhaddad
~ jhaddad$ ls -lah /tmp/bacon.txt
-rw-r--r--  1 jhaddad  wheel     0B Apr 15 13:09 /tmp/bacon.txt

Why I like it: I can very quickly fire off a command that involves changing directories without having to switch back to my pwd.

# chkconfig: 2345 64 36
# description: script for starting and stopping httpd

chkconfig –add httpd

These commands will now work:

service httpd start
service httpd stop

Additionally, apache will start when the system boots. You can accomplish this by using rc.local too, if you prefer, but I think it’s more convenient to have everything be service based where you can use chkconfig to manage startup / shutdown.

~ jhaddad$ nmap localhost
Starting Nmap 5.00 ( http://nmap.org ) at 2010-01-05 11:06 PST
Interesting ports on localhost (127.0.0.1):
Not shown: 499 closed ports, 492 filtered ports
PORT STATE SERVICE
80/tcp open http
88/tcp open kerberos-sec
548/tcp open afp
631/tcp open ipp
3306/tcp open mysql
3325/tcp open unknown
5900/tcp open vnc
9000/tcp open cslistener
10000/tcp open snet-sensor-mgmt

For more detailed information, try netstat:

netstat -an

You’ll get a breakdown of every socket open on your machine – useful for figuring out who’s connected and from where.

The OSX version of netstat lacks a few options – such as the useful ‘-p’ option to display the process id (PID) – which can be useful combined with kill to get rid of unwanted connections – for instance,an SSH tunnel accidentally left open.

Virtualization is now a commodity with several free tools available from Sun, VMWare and Xen. If you’re like me, you like to create a new, clean VM for each experiment. However, this comes with a drawback – the installation process, choosing your timezone, putting in the same password every time, etc… takes a while.

Fortunately, CentOS provides the means to automate the process via a kickstart file. The best part is, after you do an install, you’ll have a kickstart file to start working with – it’ll save all your options in /root/anaconda-ks.cfg. You can edit this file later to include other packages that you’d like to install, such as the GCC c++ libraries. You can also run other commands through yum, and customize the system-wide bashrc.

I’m only going to go over how I did the install – for the full details check out the CentOS kickstart guide

I’ve created a minimal kickstart file to do a base install without gnome, printing, and any tools I don’t find useful. I’ve disabled X completely – I have no need to boot to a GUI. I’ve also uncommented the lines to configure the drive settings, so I won’t be prompted for anything along the way; my VM should be completely ready to go once I reboot after the installation. Pretty awesome.

There’s a convenient way to run a kickstart file off a http connection, so I’ve put it the web server on my dev box. My dev box’s IP address is 192.168.1.5, and I copied the modified /root/anaconda-ds.cnf (which I’ve renamed to ks.cfg) to the server. At the installation boot prompt, I’d enter:

linux ks=http://192.168.1.5/ks.cfg

Then let it run. After a bit it’ll ready to reboot and be used. Just make sure to unmount the install DVD.

Obviously this has a lot more uses than just creating VMs, but I’m not a sysadmin, so I haven’t personally used it outside the desktop environment. There’s other tools for different distros, and third party tools for CentOS/RedHat.

For what I’ve done so far, one could argue it’s easier just to create an image of the VM and to just clone that whenever I want a new one. That’s a good solution if I was interested in always creating the same exact VM. However, using the kickstart method has several advantages. I could create a simple web app that generates new configs based on what I’ve checked off in a few lists, allowing me to quickly fire up new VMs with the right software for whatever I’m working on. I can also upgrade the version of the OS and run the same kickstart, so I don’t have to maintain some up to date starting image.

If I’ve made any mistakes, please don’t hesitate to point them out. I’m by no means a guru on the subject, I’ve just wanted to look into this topic for a while.

Some Other Useful resources

• Linux-Mag
• Red Hat Kickstart Guide

When creating a new VM through VirtualBox, you might have a problem SSH’ing into the box. You also might notice you get a 10.0.x.xx type address, even though the rest of your network is a 192.168.xx.xxx deal. Yes, the two are related.

Essentially what’s happening is the VM is sitting on it’s on little private line, where it can go out but nothing can reach it. By default, the network setting is “NAT”. If we want the VM to be accessible to the outside, we want to use Bridged networking.

This is easily solved, but requires that the VM be shut down. Go to the network second, pick an unused adapter (likely the 2nd one), enable it, and choose Bridged.

You should see this under the VM description now.

Go ahead and boot back into your VM. Fire up a terminal, run /sbin/ifconfig, and you’ll see you now have an ethernet adapter with an address you can reach.

Enjoy!

What if these types of useful feedback were available within the application itself? You could literally just type a question into your help box, and a minute later you would get answers. This would be incredibly helpful for hundreds of new users.

Answerbag has an available API that could be integrated this way. There are a number of other services that are similar and could be used as well (if they have APIs), such as answers.com, wikihow, or Yahoo! Answers.

An added benefit is now there’s a website with a VERY comprehensive FAQ that’s been indexed by google, and the people who aren’t even using the built in Q&A process can still find answers to their questions. The result? A decreased learning curve which will lead to a bigger user base.

Advantages

• Very fast response time

Answerbag was achieving about a 90% response rate on new questions within just a few minutes, and that’s just from general community.

• Does not rely on paid tech support, although it can be augmented this way by a company that can afford to do so.

Yes, you can get great answers from the community. But sometimes an official response is appreciated. A site like answerbag could add tools so that a parter company could take ownership of a category, reviewing submitted questions and answers for correctness, and modifying or locking answers after they’ve been deemed correct. It would be a departure from the current model of the site, but certainly an authoritative answer would be appreciated by a lot of people. About.com has a similar model, where experts own a particular category and maintain the content there.

• The community has more time to help people with new problems.

Since it would be easier to find older how-to pages, experts can spend less time solving the same problem over and over. They’d be more likely to help people more often, since they wouldn’t be so annoyed.

Disadvantages

• Initial answers might be inaccurate

I think in applications with a larger use base, or more tech savvy areas, this would be less of a problem. I’ve gotten some amazing answers on mailing lists and IRC channels, and I don’t see why the quality of the answers would be any different.

• Getting the first customer

Since no one is doing this yet, the hardest implementation will be the first. It’s likely a company like Microsoft or Adobe wouldn’t want to be the first in the pool for an idea like this, but they’re also the ones that could pull off the best implementation. The true power of social Q&A isn’t really apparent till you get your questions put in front of a few million eyeballs.

This would be a great opportunity for innovation in open source, in particular at the OS level. Linux adoption is lower than it could be, and it has a lot to do with the difficultly of figuring out some of the more basic tasks.

Since I no longer work on Answerbag, or it’s parent company Demand Media, I have nothing to gain at this point, except for more useful applications.

Really interesting read about how to examine what’s stored in memcached.

Peep uses ptrace to freeze a running memcached server, dump the internal key metadata, and return the server to a running state. If you have a good host ejection mechanism in your client, such as in the Twitter libmemcached builds, you won’t even have to change the production server pool. The instance is not restarted, and no data is lost.

Highlights include scalability improvements, subquery optimizations and join improvements, improved stored procedure management, out parameters in prepared statements, and new information schema additions.

EasyVMX lets you create empty VMWare images. Very useful when coupled with the VMWare player.

I used Jira about 3 years ago at Infosearch Media, which I don’t think exists any more. Anyway, it trounced bugzilla then and still does.

I like this post, it makes a few really cool points. It explains how to get a list of all tables and their engine and how to get a list of foreign keys in your schema. Very cool.

Q4M looks like a pretty cool storage engine that aims to address twitter-like features. I’ll be trying this out for myself in the near future.

Q4M (Queue for MySQL) is a message queue licensed under GPL that works as a pluggable storage engine of MySQL 5.1, designed to be robust, fast, flexible. It is already in production quality, and is used by several web services (see Users of Q4M).

lsof | grep ‘mysqld’