Voxxed Days Zürich 2023-03-16

Today I attended Voxxed Days Zürich .

Voxxed Days are a series of technical conferences for developers, affiliated with the legendary https://devoxx.com .

Future events include the Voxxed Days in Ticino on 2024-01-19 and next year’s in ZRH on 2024-03-07.

It is locally organized, with 25% of speakers from Switzerland (and 22% female speakers, great!), and sponsored by Swiss IT companies such as Swisscom, Gradle Enterprise (!), ELCA, Julius Bär, Red Hat, Ergon, Adesso, Mimacom, CSS.

Java JDK Source Code in Visual Studio Code

I’ve switched from using Eclipse to Visual Studio Code (VSC) for Java coding, and was missing the JDK Source Code in VSC.

The discussion in this bug didn’t help, because the problem was the following:

It appears that the Language Support for Java by Red Hat extension “helps” users with its (Ctrl-Shift-P) Install New JDK UI feature. Those get installed into ~/.vscode/extensions/redhat.java-1.14.0-linux-x64/jre, are entirely separate from any “system package” JDK installs - and do not appear to include the src.zip with JDK source code (at least some of them, such as Eclipse Adoptium’s Temurin).

Plain text accounting with Beancount

Plain text accounting is the idea of managing personal finances (or perhaps a small business, or club, or whatever) using a scriptable, command-line-friendly open source accounting software keeping all related data in plain text files which are easy to version control e.g. with git.

This is an alternative to using something like e.g. Intuit QuickBooks, Zoho Books, Xero, etc. or even just whatever one of your banks offers you built-in.

The Need for Speed (Part #1)

The Past

For the past 20 years, Swisscom was my ISP at home, and I had a (now) Swisscom blue Internet L subscription for Residential Customers.

The bandwidth that gave me for the last couple of years was 1 Gigabit per second (Gbps). One day when I logged in to my ISP to pay a bill, there was a message:

“Technology upgrade: With a change to the new fiber optic standard, you can achieve a speed of up to 10 Gbit/s without a monthly fee and extra cost.”

Fedora Upgrades

Following Fedora Docs’ DNF System Upgrade works reasonably well.

Here are how I resolve a few issues I run into every time I upgrade.

“The password you use to log in to your computer no longer matches that of your login keyring.”

With Automatic Login, the error message above appears e.g. when using GNOME Tweaks to auto-start Brave .

Work around it by using the Passwords and Keys (Seahorse) app to delete the Brave Safe Storage. This will break Brave’s Saved Passwords and Sync; to fix that, go to brave://sync-internals to Disable Sync (Clear Data), close Brave, and set up Sync again.

Fish is a GREAT interactive shell, but… not yet suitable for scripting! :-((

I almost :) started writing some shell scripts in Fish instead of Bash , but then discovered https://github.com/fish-shell/fish-shell/issues/510 .

This seems like a massive feature gap in Fish, at least to me. I CANNOT LIVE without set -e in Bash. ALL my scripts everywhere have that (code search seems to miss a lot of them).

Fish is great as an interactive Shell, but without this feature, I cannot start using it for more scripting.

How to launch a CLI tool in a new terminal window

Here is one way to run a CLI process in a new window, make closing that window kill that process, yet wait for the user when said process exits, e.g. not to lose some start-up error message:

gnome-terminal -- bash -c 'ls / ; read -p "Press Enter to close..."'

I used this as follows for qemu-system-x86_64 in this script :

export KERNEL
gnome-terminal -- bash -c '\
  qemu-system-x86_64 \
    (...)
    -serial stdio  -nographic  -display none \
    -kernel "$KERNEL" ; \
  read -p "QEMU has exited - press any key to close this window..."'

Note the export - that’s needed for those environment variables to work as arguments to the process in the gnome-terminal.

Debugging Linux Start-Up Speed Performance Issues

Today while LearningLinux I noticed that my ArchLinux VMs started as fast as always, but it seemed to take longer and longer for sshd to be ready. This clarified what was happening:

$ systemd-analyze
Startup finished in 1.270s (kernel) + 42.586s (userspace) = 43.857s
graphical.target reached after 42.585s in userspace.

$ systemd-analyze blame
41.769s pacman-init.service
29.292s reflector-init.service
 1.198s systemd-networkd-wait-online.service
  601ms dev-vda2.device
  393ms ldconfig.service
  360ms sshdgenkeys.service
  234ms systemd-networkd.service
  168ms systemd-tmpfiles-setup.service
  155ms systemd-timesyncd.service
  145ms systemd-resolved.service
  102ms systemd-udev-trigger.service
   94ms systemd-logind.service
   93ms systemd-udevd.service
   82ms systemd-machine-id-commit.service
   79ms systemd-journal-catalog-update.service
   69ms user@1000.service
   54ms systemd-tmpfiles-setup-dev.service
   43ms systemd-journald.service
   42ms systemd-journal-flush.service
   37ms systemd-tmpfiles-clean.service
   37ms sys-kernel-tracing.mount
   36ms kmod-static-nodes.service
   36ms dev-mqueue.mount
   36ms modprobe@configfs.service
   36ms sys-kernel-debug.mount
   36ms modprobe@drm.service
   35ms dbus.service
   35ms modprobe@fuse.service
   35ms dev-hugepages.mount


$ systemd-analyze critical-chain
The time when unit became active or started is printed after the "@" character.
The time the unit took to start is printed after the "+" character.

graphical.target @42.585s
└─multi-user.target @42.585s
  └─sshd.service @42.585s
    └─pacman-init.service @814ms +41.769s
      └─basic.target @811ms
        └─sockets.target @811ms
          └─dbus.socket @810ms
            └─sysinit.target @805ms
              └─systemd-update-done.service @798ms +5ms
                └─ldconfig.service @404ms +393ms
                  └─local-fs.target @402ms
                    └─run-user-1000.mount @20.308s
                      └─local-fs-pre.target @402ms
                        └─systemd-tmpfiles-setup-dev.service @346ms +54ms
                          └─systemd-sysusers.service @314ms +30ms
                            └─systemd-firstboot.service @293ms +20ms
                              └─systemd-remount-fs.service @258ms +29ms
                                └─systemd-journald.socket @242ms
                                  └─-.mount @237ms
                                    └─-.slice @237ms

Huh, so critical-chain shows that sshd was blocked by pacman-init… we can see that from the Before=sshd.service here:

Linux Kernel Random Number Entropy

The Linux Kernel uses “entropy” to generate random numbers:

$ cat /proc/sys/kernel/random/entropy_avail
256

$ cat /proc/sys/kernel/random/poolsize
256

$ cat /proc/sys/kernel/random/write_wakeup_threshold
256

This 256 seems to have recently changed .

Older blog posts state that 256 available entropy is too low .

I doubt that on modern 2022 Kernels, such as a 5.17 from Fedora 34 or a 5.18 in Fedora 36, this is still accurate. It now actually remains at 256 forever, even with keyboard and mouse and disk events; even a restart does not budge it.

Fedora Silverblue

See also remaining ToDo (private).

OSTree

rpm-ostree install kitty
rpm-ostree status
systemctl reboot

Flatpack

As per https://github.com/vorburger/vorburger-dotfiles-bin-etc#on-fedora-silverblue , Apps from Flatpack will have certain limitations, such as that:

• YK SK won’t work in Brave .

Troubleshooting

The blocked updates of 2022-08

As per https://fedoramagazine.org/manual-action-required-to-update-fedora-silverblue-kinoite-and-iot-version-36/ , after running e.g. rpm-ostree install kitty as e.g. in my ostree-install-gui.sh , rpm-ostree status shows what’s currently running, and what it should boot into on the next systemctl reboot: