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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for April 26th, 2017

OpenSuSE Tumbleweed – when `halt` doesn’t halt, but CLI+HLT the CPU at the end of the shutdown procedure

Posted by jpluimers on 2017/04/26

When halt is not a real halt but a suspend of the CPU.

When halt is not a real halt but a “disabling” of the CPU.

TL;DR:

Don’t use halt, use poweroff instead.

A while ago I wrote about OpenSuSE 12.x not halting after a halt:

The same holds for more recent OpenSuSE systems, but ESXi would never tell what was going on.

Recently I installed an OpenSuSE Tumbleweed system under VMware Fusion (running on Mac OS X) which indicated “The CPU has been disabled by the guest operating system.”

Log indicates a

Log indicates a “Shutdown” which in fact is a CPU not powered down.

Which — Understanding the message: The CPU has been disabled by the guest operating system (2000542) | VMware KB [WayBack] — means that halt will not power down the VM but perform a CLI + HLT on the CPU. This effectively hangs the CPU even though the console log on the right tells does a real Shutdown.

In the past – even under ESXi – a halt would just power down the system, so based on the above I did more digging and fount this very interesting answer in rhel – What is the difference between these commands for bringing down a Linux server? – Unix & Linux Stack Exchange [WayBack] which comes down to:

  • on a systemd [WayBack] based system commands like halt, reboot, shutdown all invoke systemctl [WayBack] calling for a specific target [WayBack].
  • mapping of targets and commands is as follows (quoted from the answer):
    • systemctl isolate halt.target has the shorthands:
      • shutdown -H now
      • systemctl halt
      • plain unadorned halt
    • systemctl isolate reboot.target has the shorthands:
      • shutdown -r now
      • telinit 6
      • systemctl reboot
      • plain unadorned reboot
    • systemctl isolate poweroff.target has the shorthands:
      • shutdown -P now
      • telinit 0
      • shutdown now
      • systemctl poweroff
      • plain unadorned poweroff
    • systemctl isolate rescue.target has the shorthands:
      • telinit 1
      • systemctl rescue
    • systemctl isolate multi-user.target has the shorthands:
      • telinit 2
      • telinit 3
      • telinit 4
    • systemctl isolate graphical.target has the shorthand:
      • telinit 5

For a SysV [WayBack] init runlevels versus systemd targets see:

The systemd parameters making things a bit confusing, for instance you can do reboot --halt and more of those shown in linux – Are there any good reasons for halting system without cutting power? – Super User [WayBack].

That also explains that halt without a powerdown can be useful: it for instance gives the end-user the opportunity to click the reset button instead of the power button after a halt.

–jeroen

Posted in *nix, Linux, openSuSE, Power User, SuSE Linux, systemd, SysVinit, Tumbleweed | Leave a Comment »

Easily print GitHub markdown as beautiful PDFs that – in Chrome – immediately download

Posted by jpluimers on 2017/04/26

Printing Markdown with GitPrint

Simply view any Markdown file on GitHub, then in your URL bar replace the github.com part of the URL with gitprint.com — your markdown file will be rendered to a beautiful, printable PDF.

Try an example https://gitprint.com/jquery/jquery/blob/master/README.md

Every once in a while I feel like I’ve been living under a stone for years. Today is such a day as gitprint has been around since 2014 and I only noticed it until now.

It’s cool as it prints any github page (including Markdown, RestructuredText, etc) as a PDF file.

Notes:

  • The PDF file is named after the url. For the above example, the PDF is gitprint__-jquery-jquery-blob-master-README.md.pdf
  • In my browsers, it directly starts downloading the PDF file.
  • There is a bookmarklet on the gitprint home page for easy browser integration
  • There is a gitprint Chrome Extension for even better integration into chrome (it modifies the github.com pages to add printing support)
  • It’s https too (truckloads of web-sites could learn from that).

–jeroen

Source: Easily print GitHub markdown as beautiful PDFs

Posted in Development, DVCS - Distributed Version Control, git, GitHub, Software Development, Source Code Management | Leave a Comment »

 
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