Archive for the ‘CentOS’ Tag
Cloud computing and being lazy
The need to create template images in our cloud environment is obvious. Especially with Amazon EC2 offering an amazing API and spot instances in ridiculously low prices.
In the following post I’ll show what I am doing in order to prepare a “puppet-ready” image.
Puppet for the rescue
In my environment I have puppet configured and provisioning any of my machines. With puppet I can deploy anything I need – “if it’s not in puppet – it doesn’t exist”.
Coupled with Puppet dashboard the interface is rather simple for manually adding nodes. But doing stuff manually is slow. I assume that given the right base image I (and you) can deploy and configure that machine with puppet.
In other words, the ability to convert a bare machine to a usable machine is taken for granted (although it is heaps of work on its own).
Handling the “bare” image
Most cloud computing providers today provide you (usually) with an interface for starting/stopping/provisioning machines on its cloud.
The images the cloud providers are usually supplying are bare, such as CentOS 6.3 with nothing. Configuring an image like that will require some manual labour as you can’t even auto-login to it without some random password or something similar.
Create a “puppet ready” image
So if I boot up a simple CentOS 6.x image, these are the steps I’m taking in order to configure it to be “puppet ready” (and I’ll do it only once per cloud computing provider):
# install EPEL, because it's really useful
rpm -q epel-release-6-8 || rpm -Uvh http://download.fedoraproject.org/pub/epel/6/`uname -i`/epel-release-6-8.noarch.rpm
# install puppet labs repository
rpm -q puppetlabs-release-6-6 || rpm -ivh http://yum.puppetlabs.com/el/6/products/i386/puppetlabs-release-6-6.noarch.rpm
# i usually disable selinux, because it's mostly a pain
setenforce 0
sed -i -e 's!^SELINUX=.*!SELINUX=disabled!' /etc/selinux/config
# install puppet
yum -y install puppet
# basic puppet configuration
echo '[agent]' > /etc/puppet/puppet.conf
echo ' pluginsync = true' >> /etc/puppet/puppet.conf
echo ' report = true' >> /etc/puppet/puppet.conf
echo ' server = YOUR_PUPPETMASTER_ADDRESS' >> /etc/puppet/puppet.conf
echo ' rundir = /var/run/puppet' >> /etc/puppet/puppet.conf
# run an update
yum update -y
# highly recommended is to install any package you might deploy later on
# the reason behind it is that it will save a lot of precious time if you
# install 'httpd' just once, instead of 300 times, if you deploy 300 machines
# also recommended is to run any 'baseline' configuration you have for your nodes here
# such as changing SSH port or applying common firewall configuration for instance
yum install -y MANY_PACKAGES_YOU_MIGHT_USE
# and now comes the cleanup phase, where we actually make the machine "bare", removing
# any identity it could have
# set machine hostname to 'changeme'
hostname changeme
sed -i -e "s/^HOSTNAME=.*/HOSTNAME=changeme" /etc/sysconfig/network
# remove puppet generated certificates (they should be recreated)
rm -rf /etc/puppet/ssl
# stop puppet, as you should change the hostname before it will be permitted to run again
service puppet stop; chkconfig puppet off
# remove SSH keys - they should be recreated with the new machine identity
rm -f /etc/ssh/ssh_host_*
# finally add your key to authorized_keys
mkdir -p /root/.ssh; echo "YOUR_SSH_PUBLIC_KEY" > /root/.ssh/authorized_keys
Power off the machine and create an image. This is your “puppet-ready” image.
Using the image
Now you’re good to go, create a new image from that machine and any machine you’re going to create in the future should be based on that image.
When creating a new machine the steps you should follow are:
- Start the machine with the “puppet-ready” image
- Set the machine’s hostname
hostname=uga.bait.com
hostname $hostname
sed -i -e "s/^HOSTNAME=.*/HOSTNAME=$hostname/" /etc/sysconfig/network
Run ‘puppet agent –test’ to generate a new certificate request
Add the puppet configuration for the machine, for puppet dashboard it’ll be something similar to:
hostname=uga.bait.com
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:add name=$hostname
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:groups name=$hostname groups=group1,group2
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:parameters name=$hostname parameters=parameter1=value1,parameter2=value2
Authorize the machine in puppetmaster (if autosign is disabled)
Run puppet:
# initial run, might actually change stuff
puppet agent --test
service puppet start; chkconfig puppet on
This is 90% of the work if you want to quickly create usable machines on the fly, it shortens the process significantly and can be easily implemented to support virtually any cloud computing provider!
I personally have it all scripted and a new instance on EC2 takes me 2-3 minutes to load + configure. It even notifies me politely via email when it’s done.
I’m such a lazy bastard.
It’s also been a long time since I’ve played any computer interactive game. Unfortunately a work colleague introduced me to EVE Online.
I’m usually playing EVE on Microsoft Windows, which I believe is the best platform for PC gaming.
It’s been a while since I dealt with WINE. In the old days WINE was very complicated to deal with.
I thought I should give it a try – EVE Online on CentOS.
This is a short, semi-tutorial post about how to run EVE Online on CentOS.
It’s fairly childish so even very young Linux users will be able to understand it easily.
Let’s go (as root):
# cat > /tmp/epel.conf <<EOF
[epel]
name=\$releasever - \$basearch - epel
baseurl=http://download.fedora.redhat.com/pub/epel/5/x86_64/
enabled=1
EOF
# yum -y -c /tmp/epel.conf install wine
Let’s get EVE Online (from now there’s no need for root user access):
$ cd /tmp
$ wget http://content.eveonline.com/EVE_Premium_Setup_XXXXXX_m.exe
XXXXXX is obviously the version number, which is subject to change.
Let’s install EVE:
$ wine /tmp/EVE_Premium_Setup_XXXXXX_m.exe
OK, here’s the tricky part, if you’ll run it now, the EULA page will not display properly and you won’t be able to accept it. This is because it needs TrueType fonts.
We’ll need to install the package msttcorefonts, a quick look at google suggest you can follow the instructions found here.
Let’s configure the fonts in wine:
$ for font_file in `rpm -ql msttcorefonts`; do ln -s $font_file /home/dan/.wine/drive_c/windows/Fonts; done
Run EVE:
$ wine /home/dan/.wine/drive_c/Program Files/CCP/EVE/eve.exe
It’ll also most likely add a desktop icon for you, in case you didn’t notice.
EVE works nicely with WINE, an evident that WINE has gone a very long way since the last time I’ve used it!!
I believe these instructions can be generalized quite easily for recent fedora distros just as well.
\o/
Feel free to contact me on this issue in case you encounter any problems.
I still remember my Linux nightmares of the previous century. Trying to install Linux and wiping my whole HD while trying to multi boot RedHat 5.0.
It was for a reason that they said you have to be a rocket scientist in order to install Linux properly.
Times have changed, Linux is easy to install. Perhaps two things are different, one is that objectively Linux became much easier to handle and the second is probably the fact I gained much more experience.
In my opinion – one of the reasons that Linux became easier along the years is the improving support for various device drivers. For the home users – it is excellent news. However, for the SysAdmin who deals mostly with servers and some high-end devices, the headache, I believe, still exists.
If you thought that having a NIC without a driver is a problem, I can assure you that having a RAID controller without a driver is ten times the headache.
I bring you here the story of the RocketRAID device, how to remaster initrd and driver disks and of course, how to become a rocket scientist!
WTF
With Centos 5.4 you get an ugly error in the middle of the installation saying you have no devices you can partition.
DOH!!! Because it discovered no HDs.
So now you’re asking yourself, where am I going? – Google of course.
RocketRAID 3530 driver page
And you discover you have drivers only for RHEL/CentOS 5.3. Oh! but there’s also source code!
It means we can do either of both:
- Remaster initrd and insert the RocketRAID drivers where needed
- Create a new driver disk and use it
I’ll show how we do them both.
I’ll assume you have the RocketRAID driver compiled for the installation kernel.
In addition, I’m also going to assume you have a network installation that’s easy to remaster.
Remastering the initrd
What do we have?
# file initrd.img
initrd.img: gzip compressed data, from Unix, last modified: Sun Jul 26 17:39:09 2009, max compression
I’ll make it quicker for you. It’s a gzipped cpio archive.
Let’s open it:
# mkdir initrd; gunzip -c initrd.img | (cd initrd && cpio -idm)
12113 blocks
It’s open, let’s modify what’s needed.
- modules/modules.alias – Contains a list of PCI device IDs and the module to load
- modules/pci.ids – Common names for PCI devices
- modules/modules.dep – Dependency tree for modules (loading order of modules)
- modules/modules.cgz – The actual modules inside this initrd
Most of the work was done for us already in the official driver package from HighPoint.
Edit modules.alias and add there the relevant new IDs:
alias pci:v00001103d00003220sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003320sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003410sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003510sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003511sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003520sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003521sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003522sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003530sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003540sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00003560sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004210sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004211sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004310sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004311sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004320sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004321sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004322sv*sd*bc*sc*i* hptiop
alias pci:v00001103d00004400sv*sd*bc*sc*i* hptiop
This was taken from the RHEL5.3 package on the HighPoint website.
So now the installer (anaconda) knows it should load hptiop for our relevant devices. But it needs the module itself!
Download the source package and do the usual configure/make/make install – I’m not planning to go into it. I assume you now have your hptiop.ko compiled against the kernel version the installation is going to use.
OK, so the real deal is in modules.cgz, let’s open it:
# file modules/modules.cgz
modules/modules.cgz: gzip compressed data, from Unix, last modified: Sat Mar 21 15:13:43 2009, max compression
# mkdir /tmp/modules; gunzip -c modules/modules.cgz | (cd /tmp/modules && cpio -idm)
41082 blocks
# cp /home/dan/hptiop.ko /tmp/modules/2.6.18-164.el5/x86_64
Now we need to repackage both modules.cgz and initrd.img:
# (cd /tmp/modules && find . -print | cpio -c -o | gzip -c9 > /tmp/initrd/modules/modules.cgz)
41083 blocks
# (cd /tmp/initrd && find . -print | cpio -c -o | gzip -c9 > /tmp/initrd-with-rr.img)
Great, use initrd-with-rr.img now for your installation, it should load your RocketRAID device!
A driver disk
Creating a driver disk is much cleaner in my opinion. You do not remaster a stock initrd just for a stupid driver.
So you ask what is a driver disk? – Without going into the bits and bytes, I’ll just say that it’s a brilliant way of incorporating a custom modules.cgz and modules.alias without touching the installation initrd at all!
I knew I couldn’t live quietly with the initrd remaster so choosing the driver disk (dd in short) option was inevitable.
As I noted before, HighPoint provided me only a RHEL/CentOS 5.3 driver disk (and binary), but they also provided the source. I knew it was a matter of some adjustments to get it to work also for 5.4.
It is much easier to approach the driver disk now as we are much more familiar with how the installation initrd works.
I’m lazy, I already created a script that takes the 5.3 driver package and creates a dd:
#!/bin/bash
# $1 - driver_package
# $2 - destination of driver disk
make_rocketraid_driverdisk() {
local driver_package=$1; shift
local destination=$1; shift
local tmp_image=`mktemp`
local tmp_mount_dir=`mktemp -d`
dd if=/dev/zero of=$tmp_image count=1 bs=1M && \
mkdosfs $tmp_image && \
mount -o loop $tmp_image $tmp_mount_dir && \
tar -xf $driver_package -C $tmp_mount_dir && \
umount $tmp_mount_dir && \
local -i retval=$?
if [ $retval -eq 0 ]; then
cp -aL $tmp_image $destination
chmod 644 $destination
echo "Driver disk created at: $destination"
fi
rm -f $tmp_image
rmdir $tmp_mount_dir
return $retval
}
make_rocketraid_driverdisk rr3xxx_4xxx-rhel_centos-5u3-x86_64-v1.6.09.0702.tgz /tmp/rr.img
Want it for 5.4? – easy. Just remaster the modules.cgz that’s inside rr3xxx_4xxx-rhel_centos-5u3-x86_64-v1.6.09.0702.tgz and replace it with a relevant hptiop.ko module 🙂
Edit your kickstart to load the driver disk:
driverdisk --source=http://UGAT/HA/BAIT/INC/HighPoint/RocketRAID/3xxx-4xxx/rr3xxx-4xxx-2.6.18-164.el5.img
Make sure you have this line in the main section and not meta generated in your %pre section as the driverdisk directive is being processed before the %pre section.
The OS doesn’t boot after installation
You moron! This is because the installation kernel/initrd and the one that boots afterwards are not the same!
You can fix it in one of the 3 following ways:
- Recompile the CentOS/RHEL kernel and repackage it with the RocketRAID driver – pretty ugly, not to mention time consuming.
- Build a module RPM for the specific kernel version you’re going to use – very clean but also very time consuming!
- Just build the module for the relevant kernel in the %post section – my way.
In the %post section of your kickstart, add the following:
(cd /tmp && \
wget http://UGAT/HA/BAIT/INC/rr3xxx_4xxx-linux-src-v1.6-072009-1131.tar.gz && \
tar -xf rr3xxx_4xxx-linux-src-v1.6-072009-1131.tar.gz && \
cd rr3xxx_4xxx-linux-src-v1.6 && \
make install)
The next boot obviously have a different initrd image. Generally speaking, initrd creation is done after the %post section, so you should not bother about it too much…
Server should boot now. Go play with your 12x2TB RAID array.
I hope I could teach you something in this post. It was a hell of a war discovering how to properly do all of these.
Now if you’ll excuse me – I’ll be going to play with spaceships and shoot rockets!
Introduction
Landing in a new startup company has its cons and pros.
The pros being:
- You can do almost whatever you want
The cons:
- You have to do it from scracth!
The Developers
Linux developers are not dumb. They can’t be. If they were dumb, they couldn’t have developed anything on Linux. They might have been called developers on some other platforms.
I was opted quite early about the question of:
“Am I, as a SysAdmin, going to give those Linux developers root access on their machines?”
Why not:
- They can cause a mess and break their system in a second.
A fellow developer (the chowner) who ran:
# chown -R his_username:his_group *
He came to me saying “My Linux workstation stopped working well!!!”
Later on I also discovered he was at /, when performing this command! 🙂
For his defence he added: “But I stopped the command quickly! after I saw the mistake!”
- And there’s no 2, I think this is the only main reason, given that these are actually people I generally trust.
Why yes:
- They’ll bother me less with small things such as mounting/umounting media.
- If they need to perform any other administrative action – they’ll learn from it.
- Heck, it’s their own workstation, if they really want, they’ll get root access, so who am I to play god with them?
Choosing the former and letting the developers rejoice with their root access on their machines, I had to perform some proactive actions in order to avoid unwanted situations I might encounter.
Installation
Your flavor of installation should be idempotent, in terms of letting the user destroy his workstation, but still be able to reinstall and get to the same position.
Let’s take for example the chowner developer. His workstation was ruined. I never even thought of starting to change back permissions to their originals. It would cause much more trouble in the long run than any good.
We reinstalled his workstation and after 15 minutes he was happy again to continue development.
Automatic network installations are too easy to implement today on Linux. If you don’t have one, you must be living in the medieval times or so.
I can give you one suggestion though about partitioning – make sure your developers have a /home on a different partition. It’ll be easier when reinstalling to preserve /home and remove all the rest.
Consolidating software
I consider installing non-packaged software on Linux a very dirty action.
The reasons for that are:
- You can’t uninstall it using standard ways
- You can’t upgrade it using standard ways
- You can’t keep track of it
In addition to installing packaged software, you must also have all your workstations and server synchronize against the same software repositories.
If user A installs software from repository A and user B from repository B, they might run into different behavior on their software.
Have you ever heard: “How come it works on my computer and doesn’t work on yours??”
As a SysAdmin, you must eliminate the possibilities of this to happen to a zero.
How do you do it?
Well, using CentOS – use a YUM repository and cache whatever packages you need from the various internet repositories out there.
Debian? – just the same – just with apt.
Remember – if you have any software on workstations that is not well packaged or not well controlled – you’ll run into awkward situations very soon.
Today
Up until today Linux developers in my company still posses their root access, but they barely use it. To be honest I don’t think they even really need it. However, they have it. It is also about educating the developers that they are given the root access because they are being trusted. If they blew it, it’s mostly their fault, not yours.
I’ll continue to let them be root when needed. They have proved worthy so far.
And I’ll ask you another question – do you really think that someone who can’t handle his own workstation be a good developer? – think again!
Bashing Linux 