Tuesday, March 24, 2009

SLES 11 released

Good news for SLES fans. The next major release of the product was released today. Together with SLES 11 was released enterprise-ready desktop SLED 11. Other two new products were announced as well:
  • SUSE Linux Enterprise High Availability Extension - the products integrates clustering filesystem OCFS2, cluster-aware volume manger cLVM2, distributed replicated block device DRBD and Pacemaker Cluster Stack with OpenAIS messaging and member layer. Included DRBD version 8 supports active-active replication.
  • SUSE Linux Enterprise Mono Extension - the product provides open-source cross-platform .NET framework.
What other benefits does SLES 11 bring? As you could see above, it is more modular. Some features were bundled into separate products. The next follow:
  • it is based on GNU/Linux kernel 2.6.27
  • in addition to AppArmor, it is SELinux ready
  • it provides OFED 1.4 (more about it here)
  • package management is based on fast update stack ZYpp
  • SLES 11 is greener - it supports tickless idle which is able to leave CPU in saving stake longer or it provides more granular power profiles
  • it supports swapping over NFS for diskless clients
  • it supports partitioning multiprocessor machine by CPUset System
  • virtualization layer is based on Xen 3.3
  • it is optimised for hypervisors VMware ESX, MS Hyper-V and Xen
  • default filesystem is EXT3
  • it supports kexec, kdump or SystemTap
  • it contains many other enhancements of asynchronous I/O, MPIO, NFS or iSCSI
The official product documentation isn't available yet. The release notes are here.

Quickly - SLES 10 reactivation

If you need to assign an already registered SLES 10 system to a new or different subscription the quickest way how to do it is to use suse_register command from console:
suse_register -i -f
The -f switch forces registration and -i runs registration interactively. The registration form will be available via lynx text web browser. Prepare your activation code and finish the registration.

Thursday, March 12, 2009

Running Linux kexec

The generic form of kexec command looks like
kexec -l kernel_image --initrd=kernel_initrd --append=command_line_options
The command has available many other options but the presented ones are the most important. To start kernel reset, run
kexec -e
How does it work? Linux kernel is placed in memory at defined address offset. On x86 architecture, it begins at 0x100000. Kexec is capable to call and run another kernel in the context of current kernel. It copies the new kernel somewhere into memory, moves it into kernel dynamic memory and finally copies it to the final destination which is the offset and runs it - kernel is exchanged and the reset is performed. An example how to reset running SLES 10.x kernel follows
kversion=`uname -r`
kexec -l /boot/vmlinuz-$kversion --initrd=/boot/initrd-$kversion --append="`cat /proc/cmdline`"
kexec -e
The example for RHEL 5.x is slightly different:
kexec -l /boot/vmlinuz-$kversion --initrd=/boot/initrd-${kversion}.img --append="`cat /proc/cmdline`"

Does it have any drawbacks? As I said, there may be some buggy devices which won't work after kernel reset. Typically, there are troubles with VGAs and their video memory initialization which results in garbled console after reset. The recommendation is to use normal video mode for console. You can change it with vga parameter set to zero and passed as kernel options (e.g. SLES 10 uses video framebuffer by default)
Next, the earlier version of kexec had stability issues on any other platform than x86. Today, kexec is uspported on x86, x86_64, ppc64 or ia64.

Tuesday, March 10, 2009

Fast linux reboot with kexec

Kexec is a GNU/Linux kernel feature which allows to perform kernel reboots faster. The time savings around a few minutes are the result of not performing BIOS procedures and hardware reinitialization (each hardware part - like SCSI/FC HBAs - may have own BIOS and POST which takes some amount of time to finish). As we have cold or warm reset we can newly say we have kernel reset.

The GNU/Linux boot process consists of several stages. The hardware stage, firmware stage and bootloader stage are kernel independent and are run in defined order. The hardware stage performs basic hardware tasks such device initialization and testing it. The firmware stage known on PCs as BIOS is in charge of hardware detection. The bootloader can be split into two parts. The first-level bootloader is like master boot record on PCs which calls second-level bootloader which is able to boot Linux kernel. The final stage is kernel stage.

Kexec is smart thing. It can bypass all listed stages up to kernel stage. That means it is able to bypass all the things connected with hardware and jump to the kernel stage directly. The risk is a likely unreliability of untouched devices, typically VGAs or some buggy cards.

What about requirements to try it? The kernel has to be kexec-capable plus you have to have installed kexec tools. It is not problem in today's Linux distributions. Both RHEL 5.x and SLES 10.x contains kexec-tools package which you have to install. Their production kernels are capable of doing kernel resets. On SLES 10, you can check the running kernel configuration for CONFIG_KEXEC variable.
zgrep CONFIG_KEXEC /proc/config.gz

Kexec is controlled with command line program kexec. The command takes defined values for kernel to be booted, its initrd and kernel parameters and starts the kernel reset.

Friday, March 6, 2009

VMware ESX 4.0 aka vSphere 4.0 platform

The next major release of VMware ESX platform is being prepared. The platform newly called as vSphere 4.0 is going to be based on six stones which provide:
  1. vCompute - virtualization layer, hypervisor, live migration
  2. vStorage - storage management, replication
  3. vNetwork - network management, distributed switch, Cisco Nexus switch
  4. Availability - clustering, data protection
  5. Security - VMsafe APIs, vShield Zones
  6. Scalability - dynamic resource management, distributed power management
Furthermore, the new platform will support virtual machines with 8 virtual CPUs and 256 GB of virtual memory.

The second most important part of virtual environment is centralized management. Today, we know it as VMware VirtualCenter Server. In the future, it should be called vCenter Suite. The good news, it will be available for Linux servers as well so no more Windows licenses are required.

Thursday, March 5, 2009

XenServer 5 license key

As you know, XenServer Enterprise Edition was realased for free. The license key for enterprise features and installation media are available from the download page. The new free XenServer will be released at March 25. The provided license provides high availability and StorageLink features from incoming Citrix Essentials for XenServer as well. The update to new version will be possible.

Wednesday, March 4, 2009

VCB, vcbMounter, vcbRestore ... updated

I have added another article dedicated to VMware VCB and backups over Samba or Windows shares. Here is updated list of them:
  1. VM identification - how to identify a virtual machine you intend to backup? The command vcbvmname is the answer.
  2. VM full backup - how to perform a full backup of the chosen virtual machine? The vcbmounter command can do it.
  3. VM full backup data access - how to retrieve data from the virtual machine's full backup? It is possible to mount the backup image with the mountvm command.
  4. VM file level backup - the vcbmounter command is able to perform file-level backup as well.
  5. VM backup over NFS - this article describes a simple scenario of virtual machine backup over NFS protocol.
  6. VM backup restore - it is important to know the process of restoring a virtual machine from the backup. You can use vcbrestore.
  7. VM backup with Samba or Windows share - the other approach how to perform backups of virtual machines is to use Samba or Windows shares instead of NFS server.