After the latest upgrades on my gentoo vserver system running a 3.3.0 Linux  vserver-kernel (vserver-sources-2.3.3.1), the system did not start up properly anymore. No kernel modules got loaded and even the network devices have not been available after a reboot. This is more or less the worst case, since then one has to be physically in front of the machine and can not repair the system via ssh remote login.

The kernel upgrade was not the reason for this,  but the upgrade to udev-182. This is what the log said:

Mar 21 17:20:05 mittelerde /etc/init.d/sshd[5563]: ERROR: cannot start sshd as net.eth0 would not start
Mar 21 17:20:09 mittelerde /etc/init.d/udev-mount[6075]: Udev uses a devtmpfs mounted on /dev to manage devices.
Mar 21 17:20:09 mittelerde /etc/init.d/udev-mount[6076]: This means that CONFIG_DEVTMPFS=y is required
Mar 21 17:20:09 mittelerde /etc/init.d/udev-mount[6077]: in the kernel configuration.
Mar 21 17:20:09 mittelerde /etc/init.d/udev-mount[6067]: ERROR: udev-mount failed to start
Mar 21 17:20:09 mittelerde /etc/init.d/udev[6066]: ERROR: cannot start udev as udev-mount would not start
Mar 21 17:21:06 mittelerde /etc/init.d/net.eth0[6463]: ERROR: interface eth0 does not exist

With the information “CONFIG_DEVTMPFS=y is required” the log contains the necessary hint to get things to work. The CONFIG_DEVTMPFS option had to be enabled in the kernel. Afterwards the kernel has to be recompiled. The option can be found in menuconfig under Device Drivers-> Generic Driver options and is called Maintain a devtmpfs filesystem to mount at /dev.  For getting the devfs automatically mounted at boot time it makes sense to also enable the option Automount devtmpfs at /dev, after the kernel mounted the rootfs (CONFIG_DEVTMPFS_MOUNT).

It is safe to enable these options with older udev versions. Doing so protects your system from not working any more when you get the udev update later.

Jürgen

(2 votes, average: 5.00 out of 5)

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Posted in drivers, kernel, linux | 3 Comments »

Starting with the 2.6.36 kernel, tuxonice has been removed from zen-sources. The latest official tuxonice patch, that is available at present, is for the linux kernel 3.0. In the meanwhile more recent patches, for kernel version 3.2.1 and 3.2.10, have appeared at crow202.org. So I patched the zen-stable-3.2 sources with the 3.2.1 tuxonice patch from there.

Suspend to RAM works with this kernel, at least on my Dell Precison M65 and my Desktop, as well as suspend to disk does. Furthermore I can confirm, that the 3.2.1 patch also works on the x86_64 architecture.

To get things to work, download the zen-stable-3.2 kernel tree from zen-kernel.org and extract it. Afterwards download the 3.2.1 tuxonice patch from crow202.org and apply it. After applying the patch you can continue with the standard kernel building process. As with zen-sources-3.1,  no additional patch is necessary for the zcache feature, the fix is already included in zen-stable-3.2. The zcache feature doubles RAM efficiency while providing a significant performance boosts on many workloads. The zcache feature is located under staging drivers in the kernel tree and depends on the cleancache feature, which is located under processor types and features. To enable the zcache feature, you have to pass the zcache keyword to your kernel, in example in your grub.conf.

Example: kernel /bzImage panic=60 root=/dev/hda3 zcache

For Gentoo users there is a more easy way: Download my modified overlay from [download#84] and extract it in /usr/local/portage. The overlay contains all necessary patches. Be sure to include the following line in your /etc/make.conf:

PORTDIR_OVERLAY=”/usr/local/portage”

If you want to use tuxonice include tuxonice in your USE-flags. Then emerge zen-sources and build the kernel as you like.

Tuxonice is not officially supported in current zen-sources. So If you’re using the files above, don’t report any bugs to zen-sources.org. You are on your own.

For my Precision M65 I used the following kernel config: [download#85]

For more information on the zen-sources patchset see www.zen-sources.org.

best regards

Jürgen

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Posted in gentoo, kernel, linux, zen-sources | No Comments »

Kvm has become one of the major virtualization technologies the last years. For Redhat Linux it has even become the default virtualization solution. Kvm´s IO performance is hardly competitive to other virtualization solutions when using the default options. Especially when using qcow2 images, the IO performance of kvm/qemu can be greatly improved by disabling the cache of the underlying host filesystem. This can be done by starting kvm with the cache=none option, in example with the options

-drive file=my_image.qcow2,index=0,media=disk,cache=none

instead of just supplying the image file with -hda my_image.qcow2. Then the image file is being opened using the O_DIRECT flag, bypassing the page cache. If the underlying filesystem does not support the O_DIRECT flag, this fails with the error message:

could not open disk image my_image.qcow2: Invalid argument

This is the case for an ext4 filesystem with full journaling enabled. One can easily test if the O_DIRECT flag is supported by the underlying filesystem with a simple dd command on the host:

dd if=some_file of=/dev/null iflag=direct

If the O_DIRECT flag is not supported it results in the following error:

dd: opening `some_file’: Invalid argument

Thus, if safety concerns do not apply, one does not want to use full journaling, to increase performance. The journaling options can be set either in /etc/fstab or in the filesystem itself. For the fstab case the red marked part of the following example entry has to be removed.

/dev/sda7 / ext4 defaults,noatime,nodiratime,async, data=journal 0 1

If the journaling option is set in the filesystem, this can be shown and edited with the tune2fs command. In example tune2fs -l /dev/sda7 displays information on the filesystem on /dev/sda7. If full journaling is enabled, the output contains the journal_data mount option:

Default mount options:    journal_data

The option can be removed with tune2fs -o^journal_data /dev/sda7. Afterwards the output of tune2fs -l does not contain the journal_data mount option any more:

Default mount options:    (none)

In both cases the filesystem has to be remounted to activate the changes. Afterwards qemum-kvm works with the cache=none option, as described above, and with increased IO performance.

Jürgen

References:
[1] itscblog.tamu.edu
[2] blog.nkadesign.com

(1 votes, average: 5.00 out of 5)

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Posted in linux, virtualization | 2 Comments »

Using nvidia linux drivers from version 270.X to 275.X with some graphics boards, in example the Quadro FX 350M which is built into the Dell Precision M65 notebook,  resulted in a black screen or window for OpenGL applications. Even glxgears did only output a black window. The problem has been discussed on forums.opensuse.org. A downgrade to a lower driver version, in example the version 260.X drivers is not applicable anymore, since these drivers do dot build against a recent linux-3 kernel. A upgrade to newer drivers also was not possible, since driver versions from 285.X to 295.10 did not work at all for this graphics board. Recently version 295.17 of nvidias beta driver has become available, which solves this issue. Download links are available on nvnews.net.

For gentoo users I have modified the nvidia-drivers  ebuild for the 295.17 driver. You can download my modified overlay, [download#83] and extract it in /usr/local/portage. Be sure to include the following line in your /etc/make.conf:

PORTDIR_OVERLAY=”/usr/local/portage”

Afterwards you may emerge nvdidia-drivers-295.17.

Jürgen

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Posted in 3d, drivers, graphics, linux | No Comments »

Starting with the 2.6.36 kernel, tuxonice has been removed from zen-sources. The latest official tuxonice patch that is available is for the linux kernel 3.0.  However, I found a more recent patch at gmane.org. So I patched the zen-stable-3.1 sources with this tuxonice patch.

Suspend to RAM works with this kernel, at least on my Dell Precison M65 and my Desktop, as well as suspend to disk does.

To get things to work, download the zen-stable-3.1 kernel tree from zen-kernel.org and extract it. Afterwards download the tuxonice patch from gmane.org and apply it. After applying the patch you can continue with the standard kernel building process. This time no additional patch is necessary for the zcache feature, the fix is already included in zen-stable-3.1. The zcache feature doubles RAM efficiency while providing a significant performance boosts on many workloads. The zcache feature is located under staging drivers in the kernel tree and depends on the cleancache feature, which is located under processor types and features. To enable the zcache feature, you have to pass the zcache keyword to your kernel, in example in your grub.conf.

Example: kernel /bzImage panic=60 root=/dev/hda3 zcache

For Gentoo users there is a more easy way: Download my modified overlay from [download#81] and extract it in /usr/local/portage. The overlay contains all necessary patches. Be sure to include the following line in your /etc/make.conf:

PORTDIR_OVERLAY=”/usr/local/portage”

If you want to use tuxonice include tuxonice in your USE-flags. Then emerge zen-sources and build the kernel as you wish.

Tuxonice is not officially supported in current zen-sources. So If you’re using the files above, don’t report any bugs to zen-sources.org. You are on your own.

For my Precision M65 I used the following kernel config:  [download#82]

For more information on the zen-sources patchset see www.zen-sources.org.

best regards

Jürgen

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Posted in gentoo, kernel, linux, zen-sources | No Comments »

After my last kernel upgrade I tried to build the iptables mirror target published here. The iptables mirror target takes the packet sent to your machine and returns the same packet to the machine the packet came from. Thus, let’s say someone tries to scan your machine or tries an attack he would scan his own machine or even attack his own machine. Guess what happened when I tried it with kernel versions 3.1 and 3.2 , it did not build anymore with the current linux kernel. There were some changes in the  kernels network stack. So I had to modify the iptables mirror target again to make the module work with current kernel versions. You can download the newer release for kernel version 3.1 and probably future kernels here:

[download#77]

The kernel module has been tested with kernel version 3.2.1 and 3.1. To build the module, boot the kernel you want to use the module with. Afterwards unpack the archive and run the compile.sh script to build the module. Then run the install.sh script for installing the compiled module into the /lib/modules directory for your kernel.

Now you may use the mirror target in place of the REJECT or DROP target in the INPUT, FORWARD and PREROUTING chains, like this in your firewall script:

$IPTABLES -A INPUT -j MIRROR

Beware: The use of the mirror target may lead to strange results, in example if you want to connect to an iptables protected machine which uses the mirror target, you may end up connecting to the local machine without recognizing it. It also may use much bandwith. The worst case occurs if you have two machines using the module. These machines may end up playing ping pong. So you have been warned, use with caution and at your own risk. For more information see: MIRROR target.

Downloads for older kernel versions are below. Notice the version numbering 2.6.25 works for kernels up to 2.6.27. 2.6.28 also works for 2.6.29 and 2.6.30 kernels. The 2.6.13 version of the module should work up to kernel version 2.6.16.

[download#45] [download#12] [download#13] [download#14] [download#32] [download#39] [download#46] [download#67] [download#73]

regards
Jürgen

(1 votes, average: 5.00 out of 5)

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Posted in kernel, linux, networking, security | 3 Comments »

Starting with the 2.6.36 kernel, tuxonice has been removed from zen-sources. The latest tuxonice patch that is available is for the linux kernel 3.0.  So I patched the zen-stable-3.0 sources with tuxonice. Hopefully a patch for more recent kernel versions will be available soon.

Suspend to RAM works with this kernel, at least on my Dell Precison M65 and my Desktop, as well as suspend to disk does.

To get things to work, download the zen-stable-3.0 kernel tree from zen-kernel.org and extract it. Afterwards download the tuxonice patch from tuxonice.net and apply it. For getting the zcache feature, to work you have to download and apply this patch: [download#74] The zcache feature doubles RAM efficiency while providing a significant performance boosts on many workloads.  The patch has been extracted from vserver-sources-2.3.2.5 with working zcache feature.  After applying the patch  you can continue with the standard kernel building process. The zcache feature is located under staging drivers in the kernel tree and depends on the cleancache feature, which is located  under processor types and features. To enable the zcache feature, you have to pass the zcache keyword to your kernel, in example in your grub.conf.

Example: kernel /bzImage panic=60 root=/dev/hda3 zcache

For Gentoo users there is a more easy way: Download my modified overlay from [download#76] and extract it in /usr/local/portage. Be sure to include the following line in your /etc/make.conf:

PORTDIR_OVERLAY=”/usr/local/portage”

If you want to use tuxonice include tuxonice in your USE-flags. Then emerge zen-sources and build the kernel as you wish.

Tuxonice is not officially supported in current zen-sources. So If you’re using the files above, don’t report any bugs to zen-sources.org. You are on your own.

For my Precision M65 I used the following kernel config: [download#75]

For more information on the zen-sources patchset see www.zen-sources.org.

best regards

Jürgen

(No Ratings Yet)

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Posted in gentoo, kernel, linux, zen-sources | No Comments »