Arrfab's blog Some tips and tricks, mostly around CentOS

For my new job I have to learn how to deal with Citrix XenServer (yeah, because of a mixed workload of CentOS domU's and Windows TSE servers, for which XenServer has been optimized). I liked the fact that I'm directly feeling "like home" , as Citrix XenServer dom0 is based on CentOS (still 5.3 at this time though). One of the things i had to do was to extend a Storage Repository served from an IBM DS3200 through dual HBAs, and using mpp/rdac (the default on XenServer 5.5 when it sees a rdac disk storage backend). Great, I've never had problem doing this on plain RHEL or CentOS machines, so after having extended the LUN on the IBM DS3200, I was back on the XenServer side. I always like to read the official documention before doing something (and it's even faster when you know what you're searching for) and I found this on the Citrix XenServer documentation : "How to resize a Storage repository after changing the size of an LVM-base storage" . Hmmm, WTF ? Their recipe is : "live migrate the guests, restart the host and proceed for each host"! . No, it has to work without a reboot, we're not …

Recently I received (through logwatch) several weekly reports about a mismatch in synchronized block on my md0 (/boot) device :

{style="white-space: pre-wrap;"} WARNING: mismatch_cnt is not 0 on /dev/md0

`cat /proc/mdstat` was normal though.

A `echo repair >/sys/block/md0/md/sync_action` followed by a `echo check >/sys/block/md0/md/sync_action` seems to have corrected it. Now `cat /sys/block/md0/md/mismatch_cnt` returns 0 ...

Yes i know, it's even over for more than 4 days, but i was too busy with other stuff to write a small report of the event , which i'll do later if `locate free_time` returns something useful.

In the meantime, a (funny) picture from the CentOS booth at Fosdem 2010 :D

Some member of the CentOS team will be present at the Fosdem . Feel free to come at our booth just to discuss ...

More informations on our wiki and on the Fosdem website

I was a little bit late to build latest rpm packages from spec files commited in the RPMforge svn tree. I had to deal with some external stuff and also fixing the fact that rpm-macros-rpmforge has to be installed in the chroot prior to try to build the prepared SRPM that my script/wrapper created. Now that it has been fixed and it's working (and newer rpmforge-release package to reflect all current arches), it was time to update the tree i'm building against/for . No problem for RHEL 4.8 PPC as it was ok but i updated the el5 tree to reflect RHEL 5.4 ppc. And then the problem : Mock dies completely on a bunch of errors but the first one seems obvious :

/usr/sbin/glibc_post_upgrade: While trying to execute /usr/sbin/iconvconfig.ppc child terminated abnormally
error: %post(glibc-2.5-42.ppc) scriptlet failed, exit status 115

Grr. Looking at  the`rpm -qp --changelog glibc-2.5-42.ppc.rpm` to see the differences among the glibc.ppc releases from RHEL 5.0 to 5.4 gave me some pointers :

build ppc and ppc64 base shared libraries with -mcpu=power4,
i.e. only support power4 and newer CPUs, *.a and …

Maybe some of you have already noticed but the standard Spamassassin rules don't like 2010. As explained in the SA bug 6269 , the FH_DATE_PAST_20XX rule of course matches every incoming mail starting from today .. Ouch. Time to update your rules or change your score for that rule .. I guess that an update of that rule will be available soon (i hope so) and will be fetched by a simple `sa-update` . In the meantime, time for you to fix it manually ! ;-)

What can you do when the company you work for (or should I say the people who manage the Internal Network) has decided to switch from Lotus Domino to M\$ Exchange 2007 ? Ouch ... I can't say that i'm personnally a great Lotus Domino supporter but it's stable system and a native client exists for all the current platforms (packaged in .rpm and .deb for Linux,as well as in Java installshied wizard for linux distros not using either rpm nor deb packages) .. But what when you have to switch to Exchange backend ? Up to now I always managed to have my professional laptop installed with CentOS and I surely don't want Windows on my laptop that i use for my day-to-day work :D

I had a quick look at the Exchange plugin that you can find for Evolution, but unfortunately that one (that uses OWA in the backend) can only be used against Exchange 2K or 2K3 but is incompatible with 2K7. Then i heard about rumours regarding a new Exchange/Mapi plugin (that requires a newer Evolution/gnome than the one provided in el5). I can't test it as it requires direct mapi access to the Exchange server and …

While i've used (up to now) the IBM/LSI-logic solution (aka RDAC) to support multiple paths to an IBM storage solution (aka DS4xxx and DS3xxx), it was a pain because each time you wanted to install a new kernel the procedure implied to remove the old/previous rdac module, boot with the new kernel (without mpp), rebuild mpp/rdac and creating a new initrd and then another reboot (with the new initrd containing the correct module).

I've now switched to dm-multipath instead. The basic and provided /etc/multipath.conf normally works quite ok, but if you want to tune it to support more storage vendors/solutions you really have to read the multipath documentation. Jim already blogged about the DS4700 FC backend storage .

Here is the version for the DS3200 (SAS connections) :

devices {  
  device {  
    vendor                  "IBM"  
    product                 "1726-2xx  FAStT"  
    getuid_callout          "/sbin/scsi_id -g -u -s /block/%n"  
    prio_callout            "/sbin/mpath_prio_rdac /dev/%n"  
    features                "0"  
    hardware_handler        "1 rdac"  
    path_grouping_policy    group_by_prio  
    failback                immediate  
    rr_weight               uniform  
    no_path_retry           300  
    rr_min_io               1000  
    path_checker            rdac  
  }  
}

The other day I had to configure a box that had to fetch some files from another machine and transfer those files from the DMZ to an external bank. While I usually use SFTP for that, in that specific case i had no choice and had to use FTP/SSL. First thing that hurted me is that to fetch the certificate/private key that the bank created for me, I had to use Internet Explorer on a Windows machine ! Ouch ... (yeah, they use activex on the page you have to login to for the certificate request, you *can't* use openssl yourself to send them the CSR ...) bad, bad .. and also funny that they point you to an https website to read the documentation, in which they say how to import they Root CA (which obvsiouly you had to import yourself first to read the same manual ...) .. From that time i knew i'd have troubles ..

Okay, exporting the SSL certificate/private key from Internet Exploder, using openssl to convert to PEM and i had those ready to be used on my CentOS 5.4 VM. Lftp seems good for such task and supports ssl too .. After having configured my \~/.lftprc with …

As Hp acquired Neoware several months ago, customers are searching for new thin clients .. and I received a Neoware e90 thin client (that wasn't used anymore). What could I do with it ? ... hmm, let's try to use it at home as a small appliance to host a USB HDD that can be shared . Advantage is that it doesn't consume a lot of electricity (in comparison with my Asus Barebone with a AMD x2 64) and doesn't produce noise at all .. which is also a good thing. The thin client I received has a Via Nehemiah cpu @ 800mghz and 128Mb ram. It also has a small IDE-DiskOnChip disk (32mb) but that is obviously too small to setup CentOS on it. I decided to dedicate a small 1Gb USB stick gift I received from a "well-known hypervisor" company (aka Vmware) and use it for / and swap.

I disconnected the DiskOnChip module from the motherboard and configured the bios to boot in pxe as first device and local usb-hdd for the second one (if you need a password, it's likely to be either 'dogbites' or 'DOGBITES') and i started a CentOS 5.3 setup. But that didn't work on first try : the embedded …