Website reconstruction

Submitted by Uwe Hermann on Sat, 09/02/2017 - 13:36

My website/blog/photoblog has been in a stale and broken state for quite a while now; I've finally found some time to fix everything up.

I'm rebuilding everyting from scratch (for various reasons) in Drupal 8, so for the time being various older pages and blog posts will not be available, but I'm continuously re-adding content until (more or less) everything is back up. Stay tuned!

Comments will be disabled in the future, please contact me via email for feedback/comments on blog posts or the like, I'll be updating the posts to reflect any feedback. Thanks!


My GPG key transition to a 4096-bit key

Submitted by Uwe Hermann on Fri, 01/09/2015 - 18:47

This is long overdue, so here goes:

Hash: SHA1,SHA512

I'm transitioning my GPG key from an old 1024D key to a new 4096R key.

The old key will continue to be valid for some time, but I prefer
all new correspondance to be encrypted to the new key, and will be making
all signatures going forward with the new key.

This transition document is signed with both keys to validate the transition.

If you have signed my old key, I would appreciate signatures on my new
key as well, provided that your signing policy permits that without
re-authenticating me.

Old key:

pub   1024D/0x5DD5685778D621B4 2000-03-07
      Key fingerprint = 0F3C 34D1 E4A3 8FC6 435C  01BA 5DD5 6857 78D6 21B4

New key:

pub   4096R/0x1D661A372FED8F94 2013-12-30
      Key fingerprint = 9A17 578F 8646 055C E19D  E309 1D66 1A37 2FED 8F94

Version: GnuPG v1


The new key is available from keyservers, e.g. or others.

In other news: Yes, I've not been blogging much recently, will try to do updates more often. In the mean time, you can also refer to my Twitter account for random stuff or the new sigrok Twitter account for sigrok-related posts.

Using mdadm to recover from a dead disk in a Linux RAID-1 array

Submitted by Uwe Hermann on Sat, 09/07/2013 - 21:30

2_5inch_sata_disk.pngYes, it's that time of the year again. A disk in my desktop-replacement laptop with 2 disks and a RAID-1 has died. Time for recovery.

This laptop has been running 24/7 for the last 3 years or such, so it's not too surprising that a disk dies. Surprisingly though, for the first time in a long series of dead disks, smartctl -a does indeed show errors for this disk. Here's a short snippet of those:

  $ smartctl -a /dev/sda
  Error 1341 occurred at disk power-on lifetime: 17614 hours (733 days + 22 hours)
   When the command that caused the error occurred, the device was active or idle.

   After command completion occurred, registers were:
   -- -- -- -- -- -- --
   40 41 02 1f c0 9c 40  Error: UNC at LBA = 0x009cc01f = 10272799

   Commands leading to the command that caused the error were:
   CR FR SC SN CL CH DH DC   Powered_Up_Time  Command/Feature_Name
   -- -- -- -- -- -- -- --  ----------------  --------------------
   60 f8 08 20 c0 9c 40 00  41d+01:51:50.974  READ FPDMA QUEUED
   60 08 00 18 c0 9c 40 00  41d+01:51:50.972  READ FPDMA QUEUED
   ef 10 02 00 00 00 a0 00  41d+01:51:50.972  SET FEATURES [Reserved for Serial ATA]
   ec 00 00 00 00 00 a0 00  41d+01:51:50.971  IDENTIFY DEVICE
   ef 03 45 00 00 00 a0 00  41d+01:51:50.971  SET FEATURES [Set transfer mode]

  SMART Self-test log structure revision number 1
  Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
  # 1  Short offline       Completed: read failure       90%     20511         156170102

The status of the degraded RAID array looks like this:

  $ cat /proc/mdstat
  Personalities : [raid1] 
  md1 : active raid1 sdb7[1]
       409845696 blocks [2/1] [_U]
  md0 : active raid1 sda6[0] sdb6[1]
       291776 blocks [2/2] [UU]

The [_U] means that one of two disks has failed, it should normally be [UU]. There are two RAID-1s actually, a small md0 (sda6 + sdb6) for /boot and the main md1 (sda7 + sdb7) which holds the OS and my data. Apparently (at first at least), only sda7 was faulty and got kicked out of the array:

  $ dmesg | grep kick
  md: kicking non-fresh sda7 from array!

Anyway, so I ordered a replacement disk, removed the dead disk (I checked the serial number and brand before, so I don't accidentally remove the wrong one), inserted the new disk and rebooted.

Note: In order for this to work you have to have (previously) installed the bootloader (usually GRUB) onto both disks, otherwise you won't be able to boot from either of them (which you'll want to do if one of them dies, of course). In my case, sda was now dead, so I put sdb into its place (physically, by using the other SATA connector/port) and the new replacement disk would become the new sdb.

After the reboot, the new disk needs to be partitioned like the other RAID disk. This can be done easily by copying the partition layout of the "good" disk (now sda after the reboot) onto the empty disk (sdb):

  $ sfdisk -d /dev/sda | sfdisk /dev/sdb

Specifically, the RAID disks/partitions need to have the type/ID "fd" ("Linux raid autodetect"), check if that is the case. Then, you can add the new disk to the RAIDs:

  $ mdadm /dev/md0 --add /dev/sdb6
  $ mdadm /dev/md1 --add /dev/sdb7

After a few hours the RAID will be re-synced properly and all is good again. You can check the progress via:

  $ watch -n 1 cat /proc/mdstat

You should probably not reboot during the resync (though I'm not 100% sure if that would be an issue in practice; please leave a comment if you know).

Also, don't forget to install GRUB on the new disk so you can still boot when the next disk dies:

  $ grub-mkdevicemap
  $ grub-install /dev/sdb

And it might be a good idea to use S.M.A.R.T. to check the new disk, just in case. I did a quick run for the new disk via:

  $ smartctl -t short /dev/sdb # Wait a few minutes after this.
  $ smartctl -a /dev/sdb
  SMART Self-test log structure revision number 1
  Num  Test_Description    Status                  Remaining  LifeTime(hours)  LBA_of_first_error
  # 1  Short offline       Completed without error       00%        22         -

Looks good. So far.

libsigrokdecode 0.1.1 released, more protocol decoders supported

Submitted by Uwe Hermann on Wed, 01/30/2013 - 03:18

sigrok_logo.pngJust a quick announce: We released libsigrokdecode 0.1.1 today, a new version of one of the shared libraries part of the open-source sigrok project (for signal acquisition/analysis of various test&measurement gear, like logic analyzers, scopes, multimeters, etc). I will update the Debian package soonish.

As you probably know, in addition to the infrastructure for protocol decoding, this library also ships with a bunch of protocol decoders written in Python. Currently we support 29 different ones (in various states of "completeness", improvements are ongoing).

can_pd.jpgThis release adds support for the following new protocol decoders:

Please check the announce on the sigrok blog and/or the NEWS file for the full list of changes and improvements.

Happy hacking and decoding!