21.06.2019

Ubuntu Server: How to activate kernel dumps

If you are running ubuntu server, you can add kdump on your system to write kernel dumps in case of sudden reboots etc.

Installing is very easy:
root@ubuntuserver:/etc# apt install linux-crashdump
Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following additional packages will be installed:
  binutils binutils-common binutils-x86-64-linux-gnu crash kdump-tools kexec-tools libbinutils libdw1 libsnappy1v5 makedumpfile
Suggested packages:
  binutils-doc
The following NEW packages will be installed:
  binutils binutils-common binutils-x86-64-linux-gnu crash kdump-tools kexec-tools libbinutils libdw1 libsnappy1v5 linux-crashdump makedumpfile
0 upgraded, 11 newly installed, 0 to remove and 43 not upgraded.
Need to get 2,636 B/5,774 kB of archives.
After this operation, 26.0 MB of additional disk space will be used.
Do you want to continue? [Y/n] 
Get:1 http://archive.ubuntu.com/ubuntu bionic-updates/main amd64 linux-crashdump amd64 4.15.0.46.48 [2,636 B]
Fetched 2,636 B in 0s (28.1 kB/s)     
Preconfiguring packages ...
Selecting previously unselected package binutils-common:amd64.
(Reading database ... 66831 files and directories currently installed.)
Preparing to unpack .../00-binutils-common_2.30-21ubuntu1~18.04_amd64.deb ...
Unpacking binutils-common:amd64 (2.30-21ubuntu1~18.04) ...
Selecting previously unselected package libbinutils:amd64.
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Unpacking libbinutils:amd64 (2.30-21ubuntu1~18.04) ...
Selecting previously unselected package binutils-x86-64-linux-gnu.
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Preparing to unpack .../03-binutils_2.30-21ubuntu1~18.04_amd64.deb ...
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Preparing to unpack .../10-linux-crashdump_4.15.0.46.48_amd64.deb ...
Unpacking linux-crashdump (4.15.0.46.48) ...
Processing triggers for ureadahead (0.100.0-20) ...
Setting up libdw1:amd64 (0.170-0.4) ...
Setting up kexec-tools (1:2.0.16-1ubuntu1) ...
Generating /etc/default/kexec...
Setting up binutils-common:amd64 (2.30-21ubuntu1~18.04) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Setting up makedumpfile (1:1.6.3-2) ...
Setting up libsnappy1v5:amd64 (1.1.7-1) ...
Processing triggers for systemd (237-3ubuntu10.12) ...
Processing triggers for man-db (2.8.3-2ubuntu0.1) ...
Setting up libbinutils:amd64 (2.30-21ubuntu1~18.04) ...
Setting up kdump-tools (1:1.6.3-2) ...

Creating config file /etc/default/kdump-tools with new version
Sourcing file `/etc/default/grub'
Sourcing file `/etc/default/grub.d/50-curtin-settings.cfg'
Sourcing file `/etc/default/grub.d/kdump-tools.cfg'
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-4.15.0-45-generic
Found initrd image: /boot/initrd.img-4.15.0-45-generic
done
Created symlink /etc/systemd/system/multi-user.target.wants/kdump-tools.service → /lib/systemd/system/kdump-tools.service.
Setting up linux-crashdump (4.15.0.46.48) ...
Setting up binutils-x86-64-linux-gnu (2.30-21ubuntu1~18.04) ...
Setting up binutils (2.30-21ubuntu1~18.04) ...
Setting up crash (7.2.1-1ubuntu2) ...
Processing triggers for ureadahead (0.100.0-20) ...
Processing triggers for libc-bin (2.27-3ubuntu1) ...
Processing triggers for systemd (237-3ubuntu10.12) ...
Within the installation you have to answer these questions:


After the installation the following parameter is added to the kernel cmdline:
grep -r crash /boot* |grep cfg
/boot/grub/grub.cfg:        linux    /boot/vmlinuz-4.15.0-46-generic root=UUID=a83c2a94-91c4-461a-b6a4-c7a81422a857 ro  maybe-ubiquity crashkernel=384M-:128M
/boot/grub/grub.cfg:            linux    /boot/vmlinuz-4.15.0-46-generic root=UUID=a83c2a94-91c4-461a-b6a4-c7a81422a857 ro  maybe-ubiquity crashkernel=384M-:128M
with
crashkernel=:[,:,...][@offset]
    range=start-[end] 'start' is inclusive and 'end' is exclusive 

The configuration is done via /etc/default/kdump-tools. Here the parameter to control the directory to dump the core into:

cat /etc/default/kdump-tools  |grep DIR
# KDUMP_COREDIR - local path to save the vmcore to.
KDUMP_COREDIR="/var/crash"
Next step is to reboot and verify the kernel cmdline.

#cat /proc/cmdline 
BOOT_IMAGE=/boot/vmlinuz-4.15.0-46-generic root=UUID=a83c2a94-91c4-461a-b6a4-c7a81422a857 ro maybe-ubiquity crashkernel=384M-:128M


To get a coredump just use the following commands:
root@ubuntuserver:/etc# sysctl -w kernel.sysrq=1
kernel.sysrq = 1
root@ubuntuserver:/etc# echo c > /proc/sysrq-trigger

09.06.2019

Google Jamboard ?!

By reorganising my Google drive i ran into "Jamboard"...
This is a tiny Google web application, where you can do some fast sketches but the functionality is really limited:








01.06.2019

Ubuntu Server: eBook

For testing waagent (Microsoft Azure Linux Guest Agent) i downloaded Ubuntu Server. Ubuntu advertised an ebook for administrators:

Here the short summary from this webpage:

Server provisioning: what Network Admins and IT pros need to know

This document is designed to help system administrators and DevOps focused organisations to understand bare metal server provisioning, understand its value proposition, and learn about how leading companies are using server provisioning solutions within their hyperscale environments.
Canonical’s MAAS helps organisations to take full advantage of existing hardware investments by maximising hardware efficiency, and a pathway to leverage the performance and security of hardware based solutions with the economics and efficiencies of the cloud.
With MAAS = Metal As A Service

The eBook contains 6 chapters on 20 pages:
  1. Executive summary
  2. Cloud speed with bare metal reliability and efficiency 
  3. Get the most out of your hardware investment
  4. How the smartest IT Pros let software do the work
  5. Make hardware investments more strategic 
  6. Conclusion
Ubuntus MAAS is the idea to create your own cloud with your own metal. Its about the automation of installing and provisioning hardware. There are region controllers (regiond) and rack controllers (rackd) which will manage your systems by using DNS, DHCP, PXE, TFTP and some others...
They are introducing availibility zones like they exist in Amazon Web Services or Microsoft Azure:
 If you are interested take a look here:


Get started with MAAS
To download and install MAAS for free please visit
ubuntu.com/download/server/provisioning