Select only the Jades

Some custom jq for RegEx selection of OpenStack Ironic baremetal nodes. Our Server types show up in their names. I want to be able to build lists of only the Mt. Jade Servers, which have names that look like this:

jade09-r097

openstack baremetal node list  --sort provision_state:asc   -c UUID -c Name -f json | jq '.[] | select(.Name | test("jade."))'

Debugging a Clean Failure in Ironic

My team is running a small OpenStack cluster with reposnsibility for providing bare metal nodes via Ironic. Currently, we have a handful of nodes that are not usable. They show up as “Cleaning failed.” I’m learning how to debug this process.

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Querying hostnames from beaker

If you have requested a single host from beaker, the following one liner will tell the hostname for it.

bkr job-results   $( bkr job-list  -o $USER  --unfinished | jq -r  ".[]" )   | xpath -q -e string\(/job/recipeSet/recipe/roles/role/system/@value\)

This requires jq and xpath, as well as the beaker command line packages.

For me on Fedora 33 the packages are:

  • perl-XML-XPath-1.44-7.fc33.noarch
  • jq-1.6-5.fc33.x86_64
  • python3-beaker-1.10.0-9.fc33.noarch
  • beaker-redhat-0.2.1-2.fc33eng.noarch
  • beaker-common-28.2-1.fc33.noarch
  • beaker-client-28.2-1.fc33.noarch

Merging root and home filesystems

Yocto takes up a lot of space when it builds. If the /home partition is 30 GB or smaller, I am going to fill it up. The systems I get provisioned from Beaker are routinely splitting their disks between / and /home. These are both logical volumes in the same volume group. This is easy to merge.

In order to merge them I find myself performing the following steps.

umount /home/
mkdir /althome

I then modify /etc/fstab so that the /home entry is now pointing to /althome. If I have done any work in /home/ayoung (almost always) I have to copy it to the new /home partition

mount /alhome/
cp  /althome/ayoung /home/ayoung

Once the home volume has been cleared, I can reclaim the space. The following lines will vary depending on the name of the machine.

lvremove /dev/rhel_hpe-moonshot-02-c07/home
lvresize  -L   +32.48G  /dev/rhel_hpe-moonshot-02-c07/root

I am explicitly reclaiming the size of the /home volume, which in this case is 32.48 GB.

A little bit of foresight can obviously avoid this problem; properly allocate the disks according to the workload. Requesting a machine with more disk is also an option.

But sometimes we have to fix mistakes.

Note that I use the lvdisplay command to see the names of the volumes.

In order to make use of the new space, I have to resize the file system. Since it is XFS, I use the xfs_grow command. I want the full size, so I don’t need to pass a parameter.

xfs_growfs /dev/mapper/rhel_hpe--moonshot--02--c07-root

Jamulus Server with a Low Latency Kernel on F33

I’m trying to run a Jamulus server . I got it running, but the latency was high. My first step was to add the real time kernel from CCRMA.

CCRMA no longer ships a super-package for core. The main thing missing seems to be the rtirq package.

  • installed the ccrma repo file.
  • installed the real time Kernel
  • Set the RT kernel as the default.
  • installed the rtirq scripts rpm
  • enabler the systemd module for rtirq
  • rebooted
  • cloned the Jamulus repo from git
  • configure, built, and installed Jamulus from the sources
  • added a systemd module for Jamulus
  • set selinux to permissive mode (starting Jamulus failed without this)
  • started Jamulus
  • ensured I could connect to it
  • stopped jamulus
  • set selinux to enforcing mode
  • restarted Jamulus from systemctl
  • connected from my desktop to the Jamulus server
  • Jammed

It does not seem to have much impact on the latency I am seeing. I think that is bound more by network.

Setting the Default Kernel on Fedora 33

I have a server that I want to run the Real Time Kernel from CCRMA. Once I followed the steps to get the kernel installed, I had to reboot to use it.

Rebooting on a server with a short timeout for grub is frustrating.

Since the Fedora Kernel is installed, and I want to be able to run it as a backup kernel, I had to figure out how to change the default Kernel for Grub2. Most of the docs out there assume that you can list the menu-items in the grub2 config file, but that is a thing of the past. The lines are now auto-generated from a regex match of the places where one might place the vmlinuz files.

I ended up booting the machine and looking at the grub menu, which showed three Kernels installed; two Fedora Kernels and the RT from CCRMA. The RT Kernel was the second one on the list. But Grub is 0 relative, so to set the default Kernel:

sudo grub2-set-default 1

The next time it booted, it was set to the RT kernel;

$ uname -r
5.10.2-200.rt20.1.fc33.ccrma.x86_64+rt


Working with the beaker command line

A graphical User interface has the potential ability to guide users on their journey from n00b13 to power user. If a user has never used a system before, the graphical user interface can provide a visual orientation to the system that is intuitive and inviting.

Once a user starts to depend on a system and use it regularly, they often want to automate tasks performed in that system.

I am reminded of these principals as I start making use of my company’s beaker server. I need short term access to machines of various architectures develop and test our Yocto based coding efforts.

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