Linux

Quick and dirty – modifying Boel initrd files manually

Byetzion 02/07/2007

Boel initrd files are actually compressed cramfs files. This is a menuscript for authoring and modifying these files, if needed. Assume the file in question is /tftpboot/install-initrd-i386.img:

cp /tftpboot/install-initrd-i386.img /tmp/
cd /tmp/
gzip -S .img -d install-initrd-i386.img
mount -o loop install-initrd-i386 /mnt
mkdir initrd
cd /mnt/
tar cf – . | (cd /tmp/initrd/ ; tar vxf -) # expect errors about time. It’s OK.

cd /tmp/
umount /mnt

Here you can modify the contents of /tmp/initrd for your needs. When done, continue.

mkcramfs initrd initrd.cramfs
cat initrd.cramfs | gzip -9 > initrd.modified.img

Now you can copy the file /tmp/initrd.modified.img to your /tftpboot directory.

Warning – Never delete your original initrd, in case you made a mistake and need to go back in time.

Enjoy.

Disk Storage | Linux

Better iostat visibility of ZFS vdevs

Byetzion 04/07/202111/03/2023

All ZFS users are familiar with ‘zpool iostat’ command, however, it is not easily translated into Linux ‘iostat’ command. Using large pools with many disks will result in a mess, where it’s hard to identify which disk is which, and going to a translation table from time to time, to identify a suspect slow disk….

General Hardware | Linux

High load average due to hardware issues

Byetzion 30/03/2007

Performance tuning is a sort of art. You know what you expect to reach, and you somehow strive towards that through selective tuning. Either your OS memory utilization, your network settings, NFS mount parameters, etc. I’ve been to a customer who’s server acted funny. First, it had high load average – for an idle server…

Disk Storage | Linux

Enable blk_mq on Redhat (OEL/Centos) 7 and 8

Byetzion 18/12/202127/01/2023

The IO scheduler blk_mq was designed to increase disk performance – better IOps and lower latency – on flash disk systems, with emphasis on NVME devices. A nice by-product, is that it increases performance on the “older” SCSI/SAS/SATA layer as well, when the disks in the back are SSD, and even when they are rotational…

Linux

Minimal Centos5 and SSH Server with X forwarding

Byetzion 10/10/2008

Installation of minimal selection of Centos 5 – only base, core and dialup selections, will leave a small-sized system, with the minimum required. This is a good setup to start setting up a firewall, and it lets you add any required package later using ‘yum’. This said, you cannot forward X over SSH at this…

Linux

Bluetooth Mouse on my Ubuntu Laptop – an easy feat

Byetzion 19/06/2008

I was surprised at how easy it was. You need to do the following: 1. Find your mouse’s address using ‘hcitool scan‘ 2. Verify that you can pair the two devices using ‘sudo hidd –connect XX:XX:XX:XX:XX:XX‘ 3. Edit /etc/default/bluetooth, uncomment the additional line with the HIDD_OPTIONS and set it to be “–connect XX:XX:XX:XX:XX:XX –server” 4….

Disk Storage | Scripting/Programming | Virtualization

Attach USB disks to XenServer VM Guest

Byetzion 05/05/201207/04/2020

There is a very nice script for Windows dealing with attaching XenServer USB disk to a guest. It can be found here. This script has several problems, as I see it. The first – this is a Windows batch script, which is a very limited language, and it can handle only a single VDI disk…

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