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I came across a new (to me) Linux-related website a couple months ago that rather impressed me (which is something that doesn't happen all that often). The name of the site is Linux Kernel Newbies, and it's located at http://kernelnewbies.org/.

I stumbled across the site while looking for a good kernel changelog. Most changelogs that I've been able to find discuss the changes in one of three formats

• List changes/commits made in each release candidate
• List all individual commits made during the release cycle
• Briefly summarize major changes or new features

None of these really provided the information that I was looking for. Documenting changes for each release candidate is fine if you're actually using/testing -rc kernels, but it's a pain when looking for changes from version to version because it requires looking through multiple posts or documents. The commit list approach is also fine for the gritty details, but unfortunately the summaries of each change are rather cryptic and often don't mean a lot to people not actively involved in the development. The new feature and major change approach is nice in that it's easily digestible and hits the highlights, but unfortunately it usually doesn't cover enough detail for me.

While searching for a decent changelog that was something in between the detailed commit list and a high-level summary, I found the LinuxChanges page on the Linux Kernel Newbies wiki. This is almost exactly what I've been looking for. They do a great job of describing all of the new/important features of the given kernel release, including providing links to the actual commit records if you really want the full details. They also provide a list of all individual commits,
logically grouped and sorted, which makes it much easier to understand what was changes. Finally, they even cover the highlights of new/upcoming patches are are actively being development for succeeding kernel releases.

The LinuxChanges link always displays the changelog for the most recent stable kernel release (currently 2.6.26 as I write this). Changelogs for older release can be found on the Linux26Changes page.

While the changelog is what keeps me coming back every couple of months, Linux Kernel Newbies also offers a few other useful resources that may be of interest to Linux users, such as the KernelGlossary, FAQ, and Forum. The homepage also provides links to other content on the site.

I don't have any affiliation with the site, and to be honest I haven't spent much time on the site outside of the changelog pages, but even so I found it so useful that I wanted to mention it here. Hopefully some others can benefit from this site as well.

I had an issue with free disk space (or, more appropriately, a lack there of) on my server a while back. After some investigation, I discovered that my MySQL had ballooned in size to nearly 10 GB. Actually, figuring out that the /var/lib/mysql directory was taking up so much space wasn't that hard, but understanding why and what to do about it took a while (yes, I'm sometimes slow about such things).

It turns out I had two issues. The first is that MySQL configuration, by default, maintains binary logs. These logs "contain all statements that update data or potentially could have updated it (for example, a DELETE which matched no rows). Statements are stored in the form of 'events' that describe the modifications. The binary log also contains information about how long each statement took that updated data."^[1] This is fine and all, but (again by default) these log files are never deleted. There is a (configurable) max file size for each log, but MySQL simply rolls over to a new log when it's reached. Additionally, MySQL rolls over to a new log file on every (re)start. After a few months of operation, it's easy to see how this can take up a lot of space, and my server had been running for nearly four years.

Complicating matters somewhat was the fact that the default name of the binary logs changed at some point (and, according to the current docs, now appears to have changed back. As a result, I have several gigabytes worth of logs using the old naming convention, as well as several gigabytes worth of logs using the newer convention. Yay.

Like I said, recognizing that MySQL was taking up a lot of space is not hard, but I'm paranoid about my data and didn't want to risk losing anything. So, I kept putting it off until I was literally running out of space on a near daily basis. At that point I began doing research and figured out all of the above information. I also found a quick an easy way to fix the problem.

Note: This is meant for a standalone MySQL server. I'm not sure how it may affect replication, so please do not follow these instructions on a replicated server without additional research.

First of all, the binary logs typically reside in /var/lib/mysql/. You can check to see how much space they're currently taking up with this one-liner: du -hcs /var/lib/mysql/*bin.* | tail -n 1. If it's more than a few hundred megabytes, you may want to continue on.

Next, check to see if you were affected by the name switch like I was. This is unlikely unless you've been running the server for at least a year or so, but it definitely doesn't hurt to check. Look at all *bin.* files. If they're all named the same, such as mysqld-bin.000001, then you're fine. If you see some with a different name, such as both mysqld-bin.000001 and hostname-bin.000001, then you have an outdated set of logs doing nothing but taking up space. Look at the timestamps of the .index file for each set. One should be very recent (such as today), the other not. Once you've identified the older set, go ahead and delete all of them; they're no longer being used.

Finally, for the current set, login to MySQL as an admin user (eg., mysql -u root -p). You'll want to run the following two commands:
mysql> FLUSH LOGS;
mysql> RESET MASTER;

That's it. Depending on the size and number of your logs, those two commands may take a while to run, but the end result is that any unsaved transactions will be flushed to the database, all older logs will be dropped, and the log index will be reset to 1. In my case, these two steps dropped my from 9.6 GB down to about 5 MB. Good stuff.

Of course, this is simply a workaround to the problem, not a proper solution. What I'd really like to do is either automate this process so that I don't have to worry about the logs getting out of control, or even better configure MySQL to automatically flush its own logs after some period of time or it reaches a certain total file size. I haven't found any way to do this just yet, though I admittedly haven't looked too hard. I'd appreciate any recommendations, though.

• ^[1] http://dev.mysql.com/doc/refman/5.0/en/binary-log.html

In my last post I mentioned that I recently had a hardware failure that took down my server. I needed to get it back up and running again ASAP, but due to a large number of complications I was unable to get the original hardware up and running again, nor could I get any of the three other systems I had at my disposal to work properly. Seriously, it was like Murphy himself had taken up residence here. In the end, rather desperate and out of options, I turned to Xen (for those unfamiliar with it, it's similar to VMware or Virtual Box, but highly geared towards server0. I'd recently had quite a bit of experience getting Xen running on another system, so I felt it'd be a workable, albeit temporary, solution to my problem.

Unfortunately, the only working system I had suitable for this was my desktop, and while the process of installing and migrating the server to a Xen guest host was successful (this site is currently on that Xen instance) it was not without it's drawbacks. For one thing, there's an obvious performance hit on my desktop while running under Xen concurrently with my server guest, though fortunately my desktop is powerful enough that this mostly isn't an issue (except when the guest accesses my external USB drive to backup files; for some reason that consumes all CPU available for about 2 minutes and kills performance on the host). There were a few other minor issues, but by far the biggest problem was that the binary nVidia drivers would not install under Xen. Yes, the open source 'nv' driver would work, but that had a number of problems/limitations:

1. dramatically reduced video performance, both in video playback and normal 2d desktop usage
2. no 3d acceleration whatsoever (remember, this is my desktop system, so I sometimes use it for gaming)
3. no (working) support for multiple monitors
4. significantly different xorg.conf configuration

In fairness, issues 1 and 2 are a direct result of nVidia not providing adequate specifications for proper driver development. Nonetheless, I want my hardware to actually work, so the performance was not acceptable. Issue 3 was a major problem as well, as I have two monitors and use both heavily while working. I can only assume that this is due to a bug in the nv driver for the video card I'm using (a GeForce 8800 GTS), as dual monitors should be supported by this driver. It simply wouldn't work, though. Issue 4 wasn't that significant, but it did require quite a bit of time to rework it, which was ultimately pointless anyway due to issue 3.

So, with all that said, I began my quest to get the binary nVidia drivers working under Xen. Some basic searches showed that this was possible, but in every case the referenced material was written for much older versions of Xen, the Linux kernel, and/or the nVidia driver. I tried several different suggestions and patches, but none would work. I actually gave up, but then a few days later I got so fed up with performance that I started looking into it again and trying various different combinations of suggestions. It took a while, but I finally managed hit on the special sequence of commands necessary to get the driver to compile AND load AND run under X. Sadly, the end result is actually quite easy to do once you know what needs to be done, but figuring it out sure was a bitch. So, I wanted to post the details here to hopefully save some other people a lot of time and pain should they be in a similar situation.

This guide was written with the following system specs in mind:

• Xen 3.2.1
• Gentoo dom0 host using xen-sources-2.6.21 kernel package
  • a non-Xen kernel must also be installed, such as gentoo-sources-2.6.24-r8
• GeForce 5xxx series or newer video card using nvidia-drivers-173.14.09 driver package

Version differences shouldn't be too much of an issue; however, a lot of this is Gentoo-specific. If you're running a different distribution, you may be able to modify this technique to suit your needs, but I haven't tested it myself (if you do try and have any success, please leave a comment to let others know what you did). The non-Xen kernel should be typically left over from before you installed Xen on your host; if you don't have anything else installed, however, you can do a simple emerge gentoo-source to install it. You don't need to run it, just build against it.

Once everything is in place, and you're running the Xen-enabled (xen-sources) kernel, I suggest uninstalling any existing binary nVidia drivers with emerge -C nvidia-drivers. I had a version conflict when trying to start X at one point as the result of some old libraries not being properly updated, so this is just to make sure that the system's in a clean state. Also, while you can do most of this while in X while using the nv driver, I suggest logging out of X entirely before the modprobe line.

Here's the step-by-step guide:

1. Run uname -r to verify the version of your currently running Xen-enabled kernel; eg., mine's 2.6.21-xen
2. verify that you have both Xen and non-Xen kernels installed: cd /usr/src/ && ls -l
   • eg., I have both linux-2.6.21-xen and linux-2.6.24-gentoo-r8
3. create a symlink to the non-Xen kernel: ln -sfn linux-2.6.24-gentoo-r8 linux
4. install the nVidia-drivers package, which includes the necessary X libraries: emerge -av nvidia-drivers
   • this will also install the actual driver, but it'll be built and installed for the non-Xen kernel, not your current Xen-enabled kernel
5. determine the specific name and version of the nVidia driver package that was just installed; this can be found by examining the output of emerge -f nvidia-drivers (look for the NVIDIA-Linux-* line)
6. extract the contents of the nVidia driver package: bash /usr/portage/distfiles/NVIDIA-Linux-x86_64-173.14.09-pkg2.run -a -x
7. change to the driver source code directory: cd NVIDIA-Linux-x86_64-173.14.09-pkg2/usr/src/nv/
8. build the driver for the currently-running Xen-enabled kernel: IGNORE_XEN_PRESENCE=y make SYSSRC=/lib/modules/`uname -r`/build module
9. assuming there are no build errors (nvidia.ko should exist), install the driver:
   • mkdir /lib/modules/`uname -r`/video
   • cp -i nvidia.ko /lib/modules/`uname -r`/video/
   • depmod -a
10. if necessary, log out of X, then load the driver: modprobe nvidia
11. if necessary, reconfigure xorg.conf to use the nvidia binary driver rather than the nv driver
12. test that X will now load properly with startx
13. if appropriate, start (or restart) the display manager with /etc/init.d/xdm start

Assuming all went well, you should now have a fully functional and accelerated desktop environment, even under a Xen dom0 host. W00t. If not, feel free to post a comment and I'll try to help if I can. You should also hit up the Gentoo Forums, where you can get help from people far smarter than I.

I really hope this helps this helps some people out. It was a royal pain in the rear to get this working, but believe me, it makes a world of difference when using the system.

Occasionally I have need to copy files to/from a VMware instance. The usual process for this would involve starting up the virtual machine, loading the OS, copying the files, then shutting it down and exiting VMware. However, this adds a lot of overhead to a simply file copy process. There are some easy to find utilities for doing this under a Windows host OS, but doing so under Linux has proved a bit more difficult. After a good bit of searching, I found this VMware forum post that suggested I could use a utility called vmware-mount.pl to achieve this.

Excellent. Of course, as with many things in Linux, it's not that easy.

To begin with, I had to track down a copy of the utility. I use (and highly recommend) the excellent free VMware Player to run my guest instances. It works like a champ, but unfortunately contains only a limited selection of support tools. To get a copy of vmware-mount.pl, you'll need to download the VMware Server package for Linux. Specifically, download the file labeled "VMware Server for Linux Binary (tar.gz)". This script may also come with VMware Workstation, but VMware Server, like the Player product, is free to download and use.

Once you've downloaded VMware Server, extract the contents of the tarball ( tar xf VMware-server-1.0.3-44356). Change to the bin/ directory, and copy vmware-mount.pl and vmware-loop to the bin/ directory of your installed copy of VMware Player. In my case, this this /opt/vmware/player/bin/. Verify that both scripts are executable (chmod a+x >files< if necessary).

That takes care of installing the necessary files. In order to use these scripts, however, you need support enabled for certain kernel features. Depending on your distribution this may already be enabled, but for troubleshooting purposes I'm including the three main options that I'm aware of:

• Loopback device support (allows mounting of file objects as block devices):
  Device Drivers -> Block devices -> Loopback device support
• Network block device support (not sure exactly what this does, but it's necessary):
  Device Drivers -> Block devices -> Network block device support
• Filesystem support for guest OS partition(s) (eg., FAT32 or NTFS for Windows partitions, etc.)
  File systems -> DOS/FAT/NT Filesystems -> VFAT (substitute for needed filesystems)

Note: all of these options can be compiled as modules if preferred.

Now, time to test the script. From the command line, change to a directory containing a VMware disk image (*.vmdk file). Issue the following command (substituting the name of your own disk filename):

This should like the available partitions inside the virtual disk:

In this case, I have a single NTFS partition, labeled as partition 1. Next, we'll try mounting the partition. These commands must be run as root:

These commands will create a temporary directory for testing, then mount the first partition of my VMDK file in read-only mode. You will likely be given a warning about using this program with 2.4+ kernels. In my experience it is safe to ignore this warning, so enter Y to continue. You may also be given a warning about loading the Network Block Device driver; again, enter Y to continue. If successful, switch to another console, switch to root again, and change to the mount_test/ directory. You should see a list of files and directories from the guest OS. Switch back to the first console and enter Control-C to unmount the disk.

Assuming all went well, you can now copy files to/from your virtual disk (remove the read-only switch in the above code to write to the disk). However, mounting the disk from the command line and performing all copy operations as root is not very convenient, so let's setup a method to automatically mount the disk using your standard user account. The next part of this tip utilizes techniques from my Adding Custom Actions to KDE Context Menus article, and will only work for KDE users.

To begin, we need to make KDE recognize the VMDK format by creating a file association. Within Konqueror, select Settings, Configure Konqueror.... Select the File Associations tab, then click Add... under the Known Types pane. Select application as the Group, enter the name x-vmdk, and click OK. Click Add.. in the Filename Patterns pane, enter *.vmdk, and click OK. Add another pattern for *.VMDK so KDE will recognize both cases. Enter a description, such as VMware disk image, then click OK to close the settings window.

Next, we need to tell KDE what to do with these files. Following the directions in the Adding Custom Actions to KDE Context Menus article, create the following servicemenu file:

vmdk.desktop

As you can see by the Exec line, this requires two "support" scripts, launch.sh and mountvmdk.sh. launch.sh can be found on the Adding Custom Actions to KDE Context Menus article page, and mountvmdk.sh, which is based on my mountiso.sh script from the same page, can be download here: mountvmdk.sh script. Both of these scripts must be made executable and placed in a directory in your user's path (eg, ~/bin/ or /usr/local/bin/).

The following command from mountvmdk.sh does the magic:

echo 'y' will automatically answer the question about using a 2.4+ kernel. sudo instruct the system to run the command as root (more on that later). The 1 instructs the command to mount the first partition. This shouldn't be an issue in most cases as there really isn't much of a need to create multiple partitions on a VMware disk, but keep it in mind in case you do need to work with multiple partitions. Moving along, the '-o ro' option will mount the disk in read-only mode. I'm doing this purely for safety reasons (this is a new process for me), and it should not be needed. Finally, the uid=`uid -u` option is important. This instructs the mount command to mount the disk under your regular user's name rather than as root. The id -u command will print out your uid (User ID) and pass it to the sudo mount command. Without this, you would be unable to view the files as a non-root user.

Finally, we need to tell Linux that it's ok to do this as a regular user. This is done using the sudo command. Make sure that sudo is installed on your system, then run visudo to edit the sudoers file. Explanation of the file format is way beyond the scope of this article (this simple Google search should provide plenty of examples), but you'll need to give your regular user account permission to run the vmware-mount.pl command. Additionally, if you chose to compile either the loopback network block device drivers as modules you'll need to have permission to run the modprobe command as well. Make sure that this access is only given to trusted accounts, as it can definitely be a security risk

That should do it. Save all of the files, restart Konqueror, and then right-click on a vmdk file. Select Actions, Mount VMDK from the context menu. You should now have the contents of the vmdk file accessible in a subdirectory matching the name of the original file. When finished, simply enter Ctrl-C in the xterm window to unmount the disk image and remove the temporary directory.

Much easier. :-)

One thing I love about KDE is it's incredible breadth of configuration options. I really like to tweak my environment to best suite my needs, preferences, and habits. I know what works best for me, and prefer to have my desktop environment reflect those preferences.

Despite the vast number of preferences in the KDE Control Center, there are still quite a few options for which new GUI preference setting exists. The Hidden Configuration KDE Wiki page discusses some of these options, and is worth a read if you use KDE. In particular, I was looking for a way to disable the listing and expanding of archive files in Konqueror's sidebar. This "feature" was borrowed from Windows XP (Compressed Folders), where it always bugged the hell out of me. If I wanted view the contents of Zip files in Windows Explorer then I'd unzip the damn file.

Needless to say, I was rather dismayed and disappointed when I saw this "feature" appear in a KDE upgrade. There is no GUI preference available for disabling it, but after quite a bit of internet searching I found the above Hidden Configuration page, which discusses how to do it. It's a useful resource, and I wanted to make a note of it here both for the benefit of others as well as so I can easily find the page again next time I setup KDE. :-)

If you would like to disable this feature as well, first try entering this command (as documented in the Wiki): kwriteconfig --file konqsidebartng.rc --group General --key ShowArchivesAsFolders --type bool false. You'll need to restart Konqueror for the change to take effect. If that does not work (it didn't for me), do this instead:

1. Edit ~/.kde/share/config/konqsidebartng.rc
2. Search for the option titled ShowArchivesAsFolders
3. If you ran the kwriteconfig command, you should find it under the [General] category. Delete that under [General] and instead add ShowArchivesAsFolders=false it to the top of the file
4. If you do not already have that setting in the file, simply add it to the top of the file as described in the last step
5. Save the file and restart konqueror

You should now be rid of those annoying archive folders. Enjoy.

Oh, and if you'd like to disable this feature in Windows XP as well, you can easily to so by running the following command: regsvr32.exe /u zipfldr.dll. If you choose to reenable it, you can do so simply by running regsvr32.exe zipfldr.dll.