Learnt – Change Preferred Minor MD Superblock On Software RAID Hard Disk
A hard disk drive failure on one of my servers prompted a manual software RAID 1 check and resync. Using good old SystemRescueCD, this was done but in doing so it inadvertently changed the preferred minor md superblock number on the array's hard disk drives from 3 to 124.
mdadm --misc --examine /dev/sda3 |grep 'Preferred Minor' Preferred Minor : 124
To fix this, stop the array and reassemble it again but update the superblock as it runs. Make sure you declare which hard disk drive partitions you are using as you assemble:-
mdadm --verbose --misc --stop /dev/md124 mdadm --verbose --assemble --update=super-minor --run /dev/md3 /dev/sda3 /dev/sdb3
To check it has worked, run the following 2 commands:-
mdadm --misc --examine /dev/sda3 |grep 'Preferred Minor'
Preferred Minor : 3
cat /proc/mdstat
md3 : active raid1 sdb3[0] sda3[1]
10490368 blocks [2/2] [UU]
Learnt – FFmpeg x264 Presets Changed Method
The method for calling x264 presets has changed in the latest git version of ffmpeg. The developers have also included an easy way to call the tune parameter - most often used for 'film' or 'animation'...
(OLD METHOD) -vcodec libx264 -vpre veryslow (NEW METHOD) -vcodec libx264 -preset veryslow -tune film
Learnt – Ubuntu Linux Kernel ACPI CPU Fan Bug Fix
The latest kernel update to my Ubuntu Linux MythTV computer caused the CPU fans to run at full speed (7000+ RPM), because the ACPI was not working properly. To fix this (although it's still not AS quiet as it was before) edit your Grub2 menu to add the options "acpi=force acpi_osi=linux"...
sudo -i nano /etc/default/grub GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force acpi_osi=linux" update-grub
...to bring the fans down to a more acceptable ~3500 RPM (although I reckon I can still improve on that).
Learnt – Sendmail Multiple SMTP Smart Hosts
Add colon separated server hostnames to the sendmail.cf and update your authinfo file.
define(`SMART_HOST',`[smtp.company1.com]:[auth.smtp.company2.co.uk]'
Learnt – Fetchmail preconnect command
The Fetchmail software for Linux used on my servers does not log the date and time on every check. To fix this, add the preconnect command to the configuration file:-
preconnect "date >> /home/postman/fetchmail.log"
Learnt – How To Calculate Days In A Spreadsheet
=DATE(2008;12;12) | =DATE(2009;2;19) | =DAYS360(A5;B5;1)
Objectives of 2011
- Learn something new every day.
- Lose 1 stone in weight.
- Try for the Linux Professional Institute Level III Qualification.
- Write my first HP/Palm WebOS app.
New web site launched
I launched my new web site today. It runs on WordPress and Linux. Enough said.