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Here’s a problem I ran into recently: I temporarily switched the root filesystem of my Fedora 14 install from RAID-5 to non-RAID. After I received the new SSD drives, I switched it to RAID-1 but the dracut boot sequence could not find the RAID-1 array and mount the root filesystem, ending in the errors ‘Can’t mount root filesystem. Boot has failed, sleeping forever’.

Using the dracut rdshell and rdinitdebug kernel boot options to get a shell prompt from the dracut initramfs led me to the RAID assembly failing during boot during “dracut: Autoassembling MD Raid”. I discovered manually assembling the array using mdadm –assemble … then exiting the shell would allow the boot to continue, so at least I had a temporary workaround.

To fix the dracut auto assembly of the RAID array, I did the following:

1. Booted up a Fedora Live CD so I could manipulate the RAID partitions without them being mounted/used (since they contained the root filesystem).
2. After noticing that the volume type was wrong on one of the RAID-1 member partitions by running blkid (TYPE was not “linux_raid_member”) and making sure the other partition was up-to-date with the data, I used wipefs (remember to use the -a option) on the partition with the incorrect data (and let the next step sync the data from the correct partition).
3. Set the system hostname via the hostname command, then did “mdadm –assemble /dev/md1 /dev/sda2 /dev/sdb2 –update=name –update=uuid”. This fixed the array name to be hostname:1.
4. After booting the system back up normally with the workaround, made a backup of /etc/mdadm.conf then did “mdadm –examine –scan > /etc/mdadm.conf” and made sure /etc/mdadm.conf looked correct afterward.

After these steps, the dracut boot sequence was able to auto-assemble the RAID array on boot and mount the root filesystem.

I hope this writeup helps someone who runs into a similar problem. 🙂

Have a USB-attached CyberPower System UPS but can’t get it to work with Network UPS Tools aka nut 2.6.0 (such as from the Fedora 14 or 15 rpms)? See the link to the rpms below I built.

The errors you might see (especially when running usbhid-ups -D -D -D) include “could not connect to ups”, “libusb_get_report: error sending control message: Operation not permitted”, and “Can’t retrieve Report 03: Operation not permitted”.

There is a workaround for a libusb issue affecting communication with USB CyberPower Systen UPSs in the trunk branch of the nut source code that will get into nut 2.7, but was not part of nut 2.6. See the fix here in change 2893 on nut’s trac system. Read more about the problem in this message on nut-upsuser.

To get the fix now (before the 2.7 rpms are released), I rebuilt nut 2.6 rpms (with small changes to the spec file) using the latest source snapshot from nut’s buildbot, r2978. You can download these r2978 rpm’s from here.

Have a Neato XV-11 robotic vacuum cleaner with an intriguing USB port?

Check out Hash’s post at the Random Workshop about connecting to the XV-11’s built-in serial subsystem via USB to send and receive commands and data from the vacuum.   I’m using a Linux box and minicom.  🙂

Now I just need a miniature embedded Linux platform with wifi so I can wirelessly communicate with the robot while it vacuums so I can try to create images from the LIDAR data as it maps the house…

I upgraded Fedora 12 to Fedora 14 over the weekend using PreUpgrade for the first time.   (I tried a direct yum distro-sync upgrade first but it got stuck in infinite dependency loops.)

Overall I was impressed with the download size reduction and the install speed after rebooting the system for the anaconda installer to apply the new packages.  I liked the reduction in system downtime resulting from downloading all the packages before the reboot and the smaller set of packages that were installed.

Some extra steps I had to deal with:

1. There are a couple bugs in the version of PreUpgrade that is part of Fedora 12.   This post on The Wily Blog contains the fixes to the preupgrade-cli script needed for it to run.
2. preupgrade-cli needed /etc/sysconfig/i18n to exist but it was missing on my system.   I created the file with the default values from the Fedora docs to get past this issue.

It also seemed like the install asked a few redundant questions it could have figured out before the reboot to start the install:

1. The installer asked whether to do a fresh install or an upgrade, where a PreUpgrade is obviously an upgrade.
2. The installer asked which filesystem’s installation to upgrade (there was only one on the system), and then again asked which filesystem to add to the “upgrade” list.  I believe it could have assumed the same filesystem for both questions, and even possibly set default values for all of them based on the filesystems in use when PreUpgrade was run before the reboot.
3. The installer asked which interface provided the internet connection for downloading additional packages and images, which PreUpgrade could have figured out before the reboot and passed it along.

This upgrade was the most painless Fedora or Red Hat upgrade I’ve done in years!  Almost all of my services worked afterward with no reconfiguration.  A big thanks and hats off the the Fedora team for PreUpgrade!

Did DNS partially break under Fedora 12 32-bit or x64 on your machine recently?

It was the strangest thing…  DNS problems started for me last week, even though I had not done any software updates since the beginning of April.  Machines using my caching nameserver would be fine, but some programs running locally would fail all name resolves (while others would succeed).

After much pulling of hair, gnashing of teeth, and searching of Google, I eventually ran across a bug entry and comment that helped with the following instructions:

1. yum install nss-mdns
2. Change the hosts line in /etc/nsswitch.conf to “hosts: files mdns4_minimal dns”

And name resolution is back! 🙂

Buggy software played a part in radiation overdoses given to some cancer patients, leading to deaths.

The Radiation Boom – Radiation Offers New Cures, and Ways to Do Harm – Series – NYTimes.com.