Jimmy's weblog

4/22/2016

Booting Grml via iPXE

Filed under: — jimmy @ 12:39 am

iPXE is a network boot firmware that allows you to boot ISO images over http. It’s actually part of the Grml ISO and you can find it under Addons in the boot menu. Alternatively you can download it from the iPXE website. All you need is an ISO image and the memdisk binary stored on a webserver. The ISO image needs to support the memdiskfind approach, more details can be found on the syslinux website. Grml supported it for a while, unfortunately it was broken in the last stable release but it’s working in the daily built images again.
To boot over http you need to run iPXE and press Ctrl-B after an IP address was assigned. This will give you a shell where you need to type in the following commands:

initrd http://download.grml.org/devel/grml64-small_20160415_netboot_xyz.iso
chain http://download.grml.org/devel/memdisk iso

The first one will download the ISO and the next one will download memdisk and chainboot the ISO, which is the daily build of Grml-small on the 15th of April. There’s also another ISO if you prefer Grml-full:

initrd http://download.grml.org/devel/grml64-full_20160415_netboot_xyz.iso
chain http://download.grml.org/devel/memdisk iso

If you want to boot newer daily builds, just replace the first line with the correct URL.

There’s also an easier way using iPXE menus and it only requires one command instead of two:

chain http://download.grml.org/devel/menu.ipxe

This will present you a menu where you can choose which flavor to boot.
The file menu.ipxe contains:

#!ipxe
set menu-default small

:start
menu iPXE boot menu for Grml
item --key f full    Boot Grml Full
item --key s small   Boot Grml Small

choose --default ${menu-default} selected
goto ${selected}

:full
echo Booting Grml Full over http
initrd http://download.grml.org/devel/grml64-full_20160415_netboot_xyz.iso
chain http://download.grml.org/devel/memdisk iso

:small
echo Booting Grml Small over http
initrd http://download.grml.org/devel/grml64-small_20160415_netboot_xyz.iso
chain http://download.grml.org/devel/memdisk iso

If you want to test this on your own webserver just copy your choice of ISOs, the memdisk binary and the file menu.ipxe to the root directory.

7/6/2013

I’m looking for a new job :-)

Filed under: — jimmy @ 11:55 pm

Dear readers,

Today I’m not posting about Linux or IBM Hardware but to ask for your help. I’m going to sell my company and relocate to California in the beginning of 2014. Therefore I’m looking for a cool job in the Bay Area, Debian jobs preferred. So if you know about such a job I greatly appreciate your mail (jimmy@g-tec.co.at) :)
(in other words: system administrator, developer or devops jobs closely related to FLOSS)
Thank you.

3/15/2013

Cisco WAP4410N and Gigabit Performance

Filed under: — jimmy @ 10:42 pm

In the last days I made some tests with 802.11n performance with Cisco WAP121 and WAP4410N access points to find out how much throughput I can achieve. Therefore Gigabit ethernet is required and the WAP4410N comes with a Gigabit interface (the WAP121 does not, JFYI). So I connected the AP with the included ethernet cable and forced it to use 1000 Mbps. Suddenly the link went down and never came up again. I checked the switch and everything was configured properly. Just for fun I took a look at the supplied cable and it said Cat.5, not Cat.5e. So Cisco includes a cable that does not work with Gigabit *LOL*
(Yes, under some circumstances a Cat.5 cable might work but I never tried that myself. It’s better to pay 2 Cents more for Cat.5e or Cat.6 ;-) )

5/29/2012

IBM x3100 M4 with ServeRAID C100: Testing Debian Compatibility

Filed under: — jimmy @ 2:22 pm

When IBM announced their new entry server I first checked the specs and found out, that they are going back to fakeraid controllers in the low cost machines. I was really glad a couple of years ago when those controllers disappeared but now they are back again :( Furthermore it first seemed, that the controller was not supported in the kernel of debian squeeze. So I ordered one of the first x3100 M4 to find out myself. It turned out, that there’s absolutely no problem with the squeeze kernel (Didn’t find those reports, who said that the controller is not detected, again, so I hope this false information is lost forever or at least hard to find).
Depending on the BIOS setting (modus AHCI or RAID) the controller shows up as:

00:1f.2 SATA controller: Intel Corporation Cougar Point 6 port SATA AHCI Controller (rev 05)

or

00:1f.2 RAID bus controller: Intel Corporation 82801 SATA RAID Controller (rev 05)

Although I already wasted a lot of time in my life with fakeraid controllers I decided to test the ServeRAID C100, too. Here are the lessons I’ve learned:

  • Never create the RAID in the OS because you might choose the wrong format and thus you will not see the RAID in the BIOS or IMM2 and lose the ability to monitor the health status. Create it in the BIOS or with the CLI tool.
  • If you want to install with the debian installer then you need to add option “dmraid=true” in expert mode
  • grub2 in squeeze has a bug that prevents installation on fakeraid (dirty hack: install grub from sid)
  • Booting from dmraid is broken in Debian: Bug #603319 with a dirty hack
  • I hope this posting will help you, if you really need to configure such a machine. It’s also possible and supported to upgrade the x3100 M4 with a HW-RAID controller, e.g. ServeRAID M5015 (you need the Hot-Swap Backplane, too).

    5/15/2012

    Growing Hardware RAID-5 with arcconf

    Filed under: — jimmy @ 8:26 pm

    Maybe you read my previous post “Growing Hardware RAID-5 with LVM by adding a physical disk” where I described how to add another disk to a RAID-5 with the MegaCLI tool. For older ServeRAID controllers you have to use the arcconf tool instead, e.g. ServeRAID-8k, which was shipped in the first x3650 models. There’s plenty of documentation about arcconf but how to resize a raid was hard to find. The MODIFY command is used for resizing and let’s assume that we have 3 disks in the array and add another one (same as in my previous post)

    ./arcconf modify 1 from 1 to MAX 5 0 0 0 1 0 2 0 3
    

    The syntax of arrconf is:

    ./arcconf MODIFY <Controller#> FROM <LogicalDrive#> TO [Options] <Size> <RAID#> <CHANNEL# DRIVE#> [CHANNEL# DRIVE#] [noprompt]
    

    So in our case it was Controller# 1 and LogicalDrive# 1 and MAX means to use all capacity that will be available. Raidlevel will still be level 5 and the harddisks are [0 0], [0 1], [0 2] and the new [0 3].
    To watch the status of the raid migration, use

    ./arcconf getstatus 1
    

    JFYI: To add another 146 GB SAS (15k) to the raid it took about 12 hours to rebuild the array.

    3/15/2011

    Grazer Linuxtage 2011

    Filed under: — jimmy @ 5:28 pm

    Hope to see you there :-)


    Grazer Linuxtage 2011

    5/16/2010

    Dirty dirvish hack to use “localhost” as client option

    Filed under: — jimmy @ 11:03 am

    When using dirvish you usually have to use the local hostname for the client option in default.conf. In other words, the output of the command “hostname”. If it’s different than the client option than dirvish assumes that it’s a remote transfer and uses ssh to connect. So you can not use “localhost” which would be rather straightforward ;-(
    Lately I needed dirvish on a sytem with heartbeat where two systems share one configuration but have different hostnames. Because I was so angry about this IMO stupid check with “hostname” I made a dirty hack…
    Line 258 in /usr/sbin/dirvish looks like this:

    chomp($$Options{Server} = `hostname`);
    

    I changed it to:

    chomp($$Options{Server} = localhost);
    

    This way dirvish assumes localhost as local tranfer and everything else as remote. The check itself can be found in line 520.
    Remember, this hack is really evil. There are several better ways to solve the problem.

    4/23/2010

    Linuxtage 2010

    Filed under: — jimmy @ 8:18 am

    Only one day left. I’ll be there at the grml-booth, which is a must see, again. See you there :-)


    Grazer Linuxtage 2010

    4/23/2009

    Linuxtage Graz 2009

    Filed under: — jimmy @ 8:05 am

    See you there ;-)


    Grazer Linuxtage 2009

    4/18/2006

    Posting in 37000 feet height

    Filed under: — jimmy @ 8:28 am

    Ignore this stupid posting. I just needed to make a posting while sitting in a boing 747-400 with internet connection over WLAN :-) Amazing, there don’t seem to be many places where there’s no internet available :-)
    Well, it’s not very comfortable in economy class with a notebook. Although my X60s is really small, it’s hard to manage to type as usual. But it’s possible with some practise :-)

    10/15/2005

    Sorry about forgotten comments

    Filed under: — jimmy @ 12:37 pm

    Today I was told that I should check my moderation queue. I was surprised that there’ve been comments waiting for my approvement. Then I realized that I disabled the notification mails because of the high amount of spam. I’ve enabled it again, hoping that the spam problem is now under control :-)
    I’m sorry that I missed some comments. All are now approved, read answered.

    9/9/2005

    My new domain jimmy.co.at

    Filed under: — jimmy @ 1:36 am

    Unfortunately I have to move my website and my blog to my new server because I need my old domain g-tec.co.at for my company’s website. I hope this will work without any problems. I’m sorry for the redirects ;-(
    Nevertheless, check out my new site on g-tec.co.at. It will be online in about two weeks.

    8/26/2004

    Summerbreeze Festival

    Filed under: — jimmy @ 11:44 am

    Last week I was at the summerbreeze festival, therefore I didn’t have time to post to my weblog. It was a great festival with a lot of cool bands(Finntroll rules :-) ).

    8/10/2004

    WordPress pingback

    Filed under: — jimmy @ 3:10 pm

    Just testing the pingback function, since I can’t ping mika’s blog.
    I’ve found an article about problems with pingback.
    And here is one fix.
    Unfortunately, that was not the problem. I’m now able to ping mika’s blog, if I don’t refer to a posting. But then my posting will be posted as a comment to the first posting in mika’s blog *argh*

    8/9/2004

    Modified style for wordpress

    Filed under: — jimmy @ 7:44 pm

    The darkness style is really cool, but I didn’t like the pictures. So I exchanged them and called my new style “darkone”

    Finally I’ve started my weblog, too

    Filed under: — jimmy @ 3:34 pm

    Since Mika forced encouraged me to blog I installed wordpress today. After a few modifications I feel happy now. The WordPress CSS Style Switcher was very helpful.