Roll back RPM packages – CentOS/RedHat

March 22nd, 2011 No Comments

Wouldn’t it be useful to be able to easily undo a yum/RPM change that you have just made? Well you can.
By default yum/RPM do not save roll back information. This feature can easily be enabled by doing the following, however its not perfect and can use a lot of disk space as its repackaging the files whenever you do anything. Keep an eye on /var/spool/repackage to make sure its not growing too much.

/etc/yum.conf add the line:
tsflags=repackage

/etc/rpm/macros add the line:
(create this file if it doesnt exist)
%_repackage_all_erasures 1

Once this has been enabled, any install/update/erase you do through yum or RPM will save the roll back information, allowing you to easily roll back the transaction should something bad happen.

Examples:

rpm -Uhv –rollback ’14:00′
rpm -Uhv –rollback ’9 hours ago’
rpm -Uhv –rollback ‘december 12′
rpm -Uhv –rollback ‘yesterday’

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Your WordPress.com account, xxx is not authorized to view the stats of this blog.

March 22nd, 2011 No Comments

So its fair to say that I’ve been somewhat neglecting this blog – been far too busy in the world of access control software!

Anyway, to start with a simple one, I signed into my wordpress account today and noticed that the site stats weren’t working with the following error:

Your WordPress.com account, xxx is not authorized to view the stats of this blog.

Simple fix: wordpress.com stats now seem to be integrated with jetpack. Disable the stats plugin, then install the jetpack plugin. You will need a wordpress.com account if you haven’t got one already.

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Pear – install alpha packages

July 21st, 2010 No Comments

Pear probably won’t let you install any alpha package by default (such as HTTP_Request2). Do this to install it quickly:

pear config-set preferred_state alpha
pear install HTTP_Request2
pear config-set preferred_state stable

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Configuring TFTP on Centos to backup Cisco ASA / IOS

July 2nd, 2010 No Comments

Setting up TFTP on CentOS is actually very trivial (excuse the pun)! I find it useful for backing up config from network devices such as my Cisco ASA.

Install tftp:
yum install tftp-server
chkconfig tftp on
service xinetd restart

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Increasing Partition Size on a VMWare Linux Virtual Machine

July 1st, 2010 No Comments

Naively, when creating my new VMWare ESXi virtual machines, I was expecting to be able to resize the disks with a one-liner as I have done in the past with container based virtualisation. Unfortunately it’s not quite that simple, the VM partitions will need manually resizing:

Increase the virtual disk size via Vsphere to the relevant amount (VM > edit > hard disk 1). This can be done whilst the VM is live.

Reboot the vm so it picks up the new disk size:
shutdown -r now

Check new disk size, for example this 10GB disk has been increased to 15GB, but its not yet allocated:
fdisk -l

Disk /dev/sda: 15.0 GB, 15032385536 bytes

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Install Linux Guest Support (CD2) after Citrix Xenserver installation

May 12th, 2010 No Comments

If you forget to install the Linux Guest Support cd during Xenserver installation, there are a few ways to install it post install.

Mount the CD in your KVM/DRAC etc and do:
cd /
mount /dev/cdrom /mnt/CD
cd /mnt/CD
./install.sh
follow the installation....
cd /
umount /mnt/CD

Or wget the ISO then:
mkdir -p /mnt/iso
mount -o loop XenServer-5.5.0-Update2-linux-cd.iso /mnt/iso
cd /mnt/iso
./install.sh
follow the installation....
cd /
umount /mnt/iso

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Citrix Xenserver [Errno5] Input/Output error during install

May 12th, 2010 No Comments

During installation of Citrix Xenserver 5 over DRAC (Dell Remote Access Controller) using amounted ISO, I got the error:

[Errno5] Input/Output error during install

The initial install phase started properly and it allowed me to enter all configuration settings, but failed at the end of installation. Presumably this is either an issue with the DRAC or the connection speed over which the ISO is being mounted. To get around this, you need to start the installation process as normal with the mounted ISO, then when prompted, select to continue installation from a HTTP/FTP/NFS repository. Creating a repository is easy, just grab the following files off the ISO’s and stick them on a webserver:

(ISO1)/boot/isolinux/mboot.c32 -> (WEBROOT)/xen/mboot.c32
(ISO1)/boot/vmlinuz -> (WEBROOT)/xen/vmlinuz
(ISO1)/boot/xen.gz -> (WEBROOT)/xen/xen.gz
(ISO1)/install.img -> (WEBROOT)/xen/install.img
(ISO1)/packages.main/ -> (WEBROOT)/xen/packages.main/
(ISO2)/packages.linux/ -> (WEBROOT)/xen/packages.linux/

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3 Reasons not to use UK2

May 10th, 2010 3 Comments

Today I was lured into using UK2 dot net by the temptation of a .com domain for only £5.99. Bargain I thought to myself as I clicked through the checkout. All is not as it seems though and a bargain is not always a bargain. This is why I will never be using UK2 again:

1. Although the initial domain registration is very cheap, they sting you with add-ons wherever possible. When first logging into my UK2 control panel, I noticed a total lack of functionality. All I could really do was update my nameservers or buy more stuff. In order to administer my DNS settings on their nameservers, it became apparent that I needed to buy a “DNS Management Package” for a further £9.99. Rip off or what!

2. Disgusted at the hidden costs, I decided to move my domain away from UK2. Navigating through the crappy control panel and help section, there were no domain transfer away options to be seen. In order to find the procedure for transferring my domain away, I had to contact their support team who emailed me the details. The email then indicated that there is a further £12.99 charge to transfer domains out. Sigh, more hidden costs!

3. Their support is awful. It took me 20 minutes on live chat with a monkey that didn’t understand what DNS is, to be told that I had to pay them more money to change my DNS. I considered complaining a bit more but didn’t fancy wasting hours of my time.

Thankfully one of my other good providers offers a free DNS management service even for domains not registered with them, so I was able to switch to their nameservers. /Rant /Complaint :(

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Disable weak ciphers in Tomcat

May 6th, 2010 No Comments

PCI compliance requires that weak and medium strength SSL ciphers are disabled, along with SSLv2 functionality. To achive this, just add the following to your SSL connector within server.xml and restart tomcat. sslProtocol should be set to TLS or SSLv3 and the ciphers setting should be added as below.

Typically the server.xml will be in:
/usr/share/tomcat5/conf/server.xml
/etc/tomcat5/server.xml

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Spell check your website with Firefox

April 30th, 2010 No Comments

I came across a little trick today to spell check a website you are browsing in Firefox.  It’s pretty handy if you have a live site and want to give it a once over without loading up all of your code.  To spell check the page just go to it, then paste this in the address bar:

javascript:document.body.contentEditable='true'; document.designMode='on'; void 0

If you add this code as a bookmark on your bookmarks toolbar, then you will be able to spell check a site just by clicking on the bookmark button :)

This javascript makes the whole webpage editable, and therefore runs it thought the spellchecker. Nice!

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