Tag Archives: Linux

WordPress Under Attack

If you run a wordpress blog, you really should  be aware that there is a global attack on wordpress blogs going on.

It’s coming from a bot net and is an attempt to find blogs that have their admin account enabled with easy to guess passwords.

I noticed the attack a couple of months ago when, while watching my web server log scrolling by, I noticed a significant number of attempts to use the wp-login.php script from random IP addresses.

A bit of research turned up information on the global attack.

Obviously I wanted to do something about it to protect my server.

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Xen, LVM, and Grub

I ran into an interesting problem with my new server the other day.

Due to a hardware problem with an external USB hard drive, I had to reboot the XEN host.

I had to do the reboot remotely … so I couldn’t intervene if something went wrong.  Yes, you guessed it, something did go wrong.

When I finally got home I found the system trying to boot ‘bree’ … which is one of the XEN guest machines.

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CentOS Upgrade

Well, I’m pretty pleased with CentOS so far.

I just completed a minor version upgrade (5.5 to 5.6) via yum and it went very smoothly.  This involved 3 virtual guest and one host (the guests run inside the host).

I had one small glitch with the RPM database on middle-earth.  Some dependencies were screwed up, but that was corrected by running yum clean all.

In order to speed things up, I’m going to be mirroring the most current CentOS package repository on middle-earth … that way I can get the updates done much quicker (installs too).

Of course I still have to move a bunch of the applications to the virtual machine’s.  I think I’m close to being able to retire gondor.  Moving rivendell is going to a major effort.

Virtualization Advice

I need some virtualization advice.

I’m currently running this blog, among others, on XEN 3.1.2 based virtualization on CentOS 5.5.

At the present time, I have three physical machines running … rivendell, gondor, and middle-earth.

Middle-earth”is the XEN host.

Rivendell and gondor are stand alone servers running Fedodra 10.

Currently gondor is primarily a web server and backup mail delivery server.

Rivendell is the main system and acts as a NIS server, MySQL server, samba file server, chat server, mail server, etc.

My goal is to migrate all the functions from rivendell & gondor to XEN instances on middle-earth.

My questions relate to where to run services, file systems, and processor allocation.

Specifically …

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Virtualization

One of the goals I have for the new system is to replace the two existing servers.

My current plan is to do this via virtualization.

There are a number of virtualization options available … each with advantages & disadvantages.

The virtualization products I’m currently consider are:

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‘Tis The Season to Upgrade! (or not)

Yes, it’s that time of year again … UPGRADE TIME!

With the release of Fedora 12 a few months ago, I’m taking the holiday break from work to get my servers up to a more current version of Linux.

The fact that Fedora 10, the version of Linux I am currently running, is no longer going to be updated added a little more incentive.

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Temporary LIBXML2 solution

Ginny has been bugging me about the problem she’s been having posting to her blog from the iPhone and other third party tools that she uses.

The problem has been narrowed down to a bug in LIBXML2 that causes leading angle brackets “<” to be stripped off of posts when processed through the XMLRPC support in PHP.   I logged the issue in the WordPress bug tracker, and the consensus is that the problem started manifesting after an automatic update applied by Fedora 8.

Well, to solve the problem I’ve moved Ginny’s blog to a temporary server running in a base Fedora 8 install in a VMWare instance.   Luckily WordPress stores most of it’s content in the MySQL database (not the images, unfortunately).   A bit of NFS magic to mount the appropriate directory in the virtual system, and it’s working fine.   The server itself only has Apache, PHP, MySQL client, SSH, and a few other bits & pieces to keep it running.   No automatic updates, GUI, compilers, etc.

Once the bug is fixed (either WordPress, using a different XML processing mechanism, or LIBXML2) I’ll move her server back to the main server.

In the mean time, her blog is going to run in the virtual machine ‘Hobbittown’ (named because it’s small).

Another upgrade, another problem

Yep, it happened again … about this time last year I was trying to upgrade my servers to Fedora Core 6 and ran into some problems.

Well, I decided it was time to upgrade to Fedora 8 … and, since I have time off, I figured this was a fine time to do it again.

Bad move.

Of course, in retrospect … there never would have been a good time to do the upgrade, based on the problems I encountered. At least I know my backup procedure is fairly good now.

I had been planning this upgrade for weeks … everything was set. In fact, the first half of the upgrade went smooth as silk. I upgraded the main web server (gondor) to Fedora 8 and it went pretty nicely. Only two issues, both of which were solved after a little research.

This gave me the confidence to proceed to upgrade Rivendell to Fedora 8.

I started the upgrade by booting from the CD so I could install Fedora from the DVD ISO image I had on a USB hard drive. Problem is, the system wouldn’t boot this way.

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SpamAssassin problem on Fedora 6

Yesterday I found that the RPM database on my Fedora Core 6 linux system’s were corrupted and that the regularly running update process was failing (without telling me, unfortunately).

After fixing the RPM database problem (rm -f /var/lib/rpm/__db.* && rpm -vv --rebuilddb) and running the update (yum update), I found that SpamAssassin’s update process wasn’t working anymore.

root@rivendell ~]# sa-update
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/i386-linux-thread-multi/Scalar/Util.pm line 30.

Apparently one of the updates that were applied in the mass update caused SpamAssassin to break.

The same problem occurred when I tried to test the SpamAssassin rules.

root@rivendell ~]# spamassassin --lint
Use of uninitialized value in concatenation (.) or string at /usr/lib/perl5/5.8.8/i386-linux-thread-multi/Scalar/Util.pm line 30.

A bit of research turned up this link.

Luckily the fix was fairly easy … just update the Scalar-List-Utils CPAN package …

perl -MCPAN -e 'install "G/GB/GBARR/Scalar-List-Utils-1.18.tar.gz"

… and everything worked fine again.