Bjoern Olausson

Linux
KVM host settings PDF Print E-mail
  
Sunday, 06 December 2009 22:14
Some things i came across when I was setting up a new Linux KVM host:

  • Which scheduler on the host ist the one to go for?
I was playing around with the available schedulers but thankfully someone else did that before.
See Bugreport  #505695 on the RedHat Bugzilla.
So apparently the best suited scheduler for a KVM host is the "deadline" scheduler.

 

  • Which scheduler on the VM ist the on to go for?
In the "Redhat Oracle 10G best practices document" (PDF) they suggest the "noop" scheduler.
It states, that with the "noop" scheduler, the host is able to optimize the I/O request, which is what we want.

 

Further, the RedHat Bugreport #505695 suggest  to "put virtio-blk devices in rotational mode".
At least I couldn't find a kernel parameter to enable this at boot time (if someone knows, please let me know),
so this has to be done on every VM by hand (or add the following to a start script like /etc/conf.d/local.start):

# for device in /sys/block/vd*/queue/rotational ; do echo "1" > ${device} ; done

The VMs should be started without a "drive cache". For "qemu-kvm" start the VMs with

# -drive cache=off

And don't forget to enable "KSM" for page merging in Kernel 2.6.32 and later. Why? See here.
Last Updated ( Tuesday, 08 December 2009 15:23 )
 
Linux - Sane - Epson V300 Photo PDF Print E-mail
  
Sunday, 08 November 2009 22:40
Since my Umax Astra 2200 SCSI/USB scanner gave up on his duty, I was searching for a worthy successor.
And finally I found one...

 

To all those scanner seeking Linux users:
Epson Perfection V300 Photo works like a charm!
It's supported via the sane epkowa backend.

 

For the Gentoo Linux users, just emerge
and the scanner works flawless with Xsane, Iscan and skanlite

 

One drawback:
The buttons are not working and for now I had no time to look into this, but a working "copy" Button would be nice :-)
Last Updated ( Sunday, 08 November 2009 23:09 )
 
Fritz!Box 7170 as remote console PDF Print E-mail
  
Sunday, 20 July 2008 23:09

I finally managed to get my USB-Serial converter running on the Fritz!Box 7170.

So now I can use the Fritz!Box as a remote console to monitor my little server :-)

Hit Read more... to learn how to do this... 

 

Last Updated ( Wednesday, 06 August 2008 10:34 )
 
Maintain Gentoo system PDF Print E-mail
  
Saturday, 10 November 2007 03:32

It's no problem if you follow these commands
 
 Do the following to keep your system up-to-date and rock solide:

emerge sync #(if you have esearch installed consider using esync)
emerge -uDav world
emerge -av depclean
revdep-rebuild
etc-update #(or dispatch-conf or cfg-update)

Run this commandset once a week or how often you want. But I think once a week is okay.

If you are concerned about your securety run this command every day

glsa-check -f all

Note that it is still in developement (http://www.gentoo.org/proj/en/portage/glsa-integration.xml)

Unmerging packages with its depending packages:

emerge --pretend --unmerge PACKAGENAME `equery depends PACKAGENAME | grep --invert-match Searching`

If packages fail, use untill to skip them (can break system consistency. Run emerge -uDNva world after this):

emerge -uDN world || until emerge --resume --skipfirst ; do emerge --resume --skipfirst ; done

 

 
Obsolete packages PDF Print E-mail
  
Friday, 09 November 2007 15:05
Portage magic: Identify obsolete packages

Gentoo developer Brian Harring designed a clever way to identify all merged versions of packages not available in Portage anymore -- both the official tree and packages from PORTDIR_OVERLAY. Here is the method he came up with, packing as much Python neatness as fits on a single command line
 
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