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

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Archive for the ‘Linux’ Category

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Eject USB drives / eject command – Unix & Linux Stack Exchange

Posted by jpluimers on 2020/07/20

I always thought than an umount /dev/sdX# for all partitions on /dev/sdX was enough for USB devices to be ejected, but there are three commands that (on most systems) actually power down USB drives (or USB to SD card adapters):

  • udisks --detach /dev/sdX (requires the udisks package which is obsolete)
  • eject /dev/sdX seems not to be enough on some systems; it is part of the util-linux package
  • udisksctl power-off -b /dev/sdX is equivalent to the udisks command; it is part of the udisks2 package.

These will ensure that the disk is not part of the fdisk --list output any more.

The opposite of these is sg_start, which is from the sg3_utils package.

Source: [WayBack] Eject USB drives / eject command – Unix & Linux Stack Exchange

On MacOS, you can use  diskutil eject /Volumes/<LABEL> (source: answer by efesaid on [WayBack] Eject USB drives / eject command – Unix & Linux Stack Exchange)

–jeroen

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

openSUSE forums tips

Posted by jpluimers on 2020/07/17

A few tips from posting to the openSUSE forums, learned from banging my head to the wall too often.

  • They are at https://forums.opensuse.org/forum.php
  • The forum software can be very slow at times taking ~tens of seconds for loading a post:
    • loading multiple posts or pages of posts you are interested in multiple tabs speeds up your reading a lot
  • Answers on the post often are along the form “has been answered before” without pointing to the actual link, even if the post is marked with a read icon, for instance in [WayBack] No option to “keep me logged in on this device” with Novell/openSUSE login?
  • Your email is not your username, so do not use it during logon: [WayBack] Lousy log in
  • The search function in the forum is horrible.
  • The forum software is proprietary (vBulletin – Wikipedia) and has a
  • When writing/replying to posts:
    1. Edit your answer off-line, because
      • you will automatically be logged off even if the forum indicates you are still logged on (there is no count down of the activity timer), see
      • when you re-logon, your carefully edited text has been lost from the cache
    2. Never use formatting, either auto-introduced, or introduced while pasting, avoid BB-code
      1. Reasoning
      2. Though the forum supports BB code, NNTP news readers do not, and the added formatting gives quite a mess
      3. Use the text (“Source mode”) version of the editor, by first clicking the left most button: “Source”

        • After this, the third and fourth button get greyed out:
      4. Remove formatting button is the second from the left (in both text and WYSIWIG mode): “Remove format”
      5. If you are in WYSIWIG mode, then always paste using the third button from the left that strips formatting: “Paste as plain text”
      6. NEVER EVER paste with formatting with the fourth button from the left: “Paste from Word”

–jeroen

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

GitHub – gamelinux/passivedns: A network sniffer that logs all DNS server replies for use in a passive DNS setup

Posted by jpluimers on 2020/07/15

Cool tool: [WayBack] GitHub – gamelinux/passivedns: A network sniffer that logs all DNS server replies for use in a passive DNS setup via [WayBack] How to log all my DNS queries? – Unix & Linux Stack Exchange (thanks mxmlnkn!).

It listens on port 53 for DNS requests then logs them to a file on regular intervals aggregating similar requests.

Usage is simple:

Read the rest of this entry »

Posted in *nix, *nix-tools, Development, DevOps, Infrastructure, Linux, openSuSE, Power User, SuSE Linux, Tumbleweed | Leave a Comment »

Marrying U-Boot, uEFI and grub2 – Alexander Graf – openSUSE…

Posted by jpluimers on 2020/07/13

A very insightful talk: “Marrying U-Boot, uEFI and grub2 – Alexander Graf – openSUSE…”

Booting is hard. Booting in the ARM world is even harder. State of the art are a dozen different boot loaders that may or may not deserve that name. Each gets configured differently and each has its own pros and cons.

As a distribution this is a nightmare. Configuring each and every one of them complicates code that really should be very simple.

To solve the problem, we can just add another layer of abstraction (grub2) on top of another layer of abstraction (uEFI) on top of another layer of abstraction (u-boot). Follow me on a journey on how all those layers can make life easier for the distribution and how much fun uEFI really is.

After this talk, you will know how ARM systems boot, what uEFI really means, how uEFI binaries interact with firmware and how we are going to move to uEFI based boot on openSUSE for ARM.

Usually known as agraf on-line, [WayBack] Alexander Graf – Open IoT & ELC 2017 is an impressive guy:

Alexander Graf

SUSE
KVM Wizard
Nürnberg Area, Germany
LinkedInConnect
Alexander started working for SUSE about 9 years ago. Since then he worked on fancy things like SUSE Studio, QEMU, KVM and openSUSE on ARM. Whenever something really useful comes to his mind, he tends to implement it. Among others he did Mac OS X virtualization using KVM, nested SVM, KVM on PowerPC and a lot of work in QEMU for openSUSE on ARM. He is the upstream maintainer of KVM for PowerPC, QEMU for PowerPC and QEMU for S390x.

Slides: [WayBack] Marrying U-Boot, UEFI and grub.pdf

There are 2 videos on YouTube (view them below):

A few things I learned

Boot sequence:

  1. Raspberry Pi has a tiny boot ROM
  2. It loads the firmware in the GPU (for Raspberry this is a Raspberry Foundation provided binary)
  3. The firmware loads U-Boot
  4. U-Boot loads grub2
  5. grub2 can have many modules (like file system drivers) and loads the kernel

Alexander pushed the U-Boot stuff up stream, but the FreeBSD team was the first to actually boot a full OS from it.

Relations:

  • uEFI/EFI is a set of specs that define the API
  • U-Boot is the firmware implementing uEFI, so your machine behaves as a PC making booting a lot more standardised, starting at handing off to a regular grub2 boot process
  • U-Boot loads grub2

U-boot:

–jeroen

References:

Images

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

openSUSE:Standards Rpm Metadata – openSUSE: Repository layout

Posted by jpluimers on 2020/07/09

For my link archive: [WayBack] openSUSE:Standards Rpm Metadata – openSUSE: Repository layout.

It is not fully up to date any more on primary.xml.gz, so here are my notes for the aarch64 version of Tumbleweed:

  1. Inspect http://download.opensuse.org/ports/aarch64/tumbleweed/repo/oss/repodata/repomd.xml [WayBack] for the name of *-primary.xml.gz (in this case http://download.opensuse.org/ports/aarch64/tumbleweed/repo/oss/repodata/d701c298b21d0b995c9560f9cfcc84685cb916deacc4f4c4a613a9b9d8f5aa57-primary.xml.gz [WayBack]
  2. Download that .gz file and uncompress it
  3. Inspect the *-primary.xml from it, look inside the metatadata root element for a package having a name element with value openSUSE-release: that package element now has a version element having a ver attribute containing the version text.

–jeroen

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

Raspberry Pi, Tumbleweed, btrfs

Posted by jpluimers on 2020/06/15

I want to use btrfs as filesystem on a Raspberry Pi with opensuse Tumbleweed.

It is hard to find out how, so here are a few links that should help me from “opensuse” “tumbleweed” “btrfs” “raspberry” pi:

–jeroen

Posted in *nix, *nix-tools, Development, Hardware Development, Linux, openSuSE, Power User, Raspberry Pi, SuSE Linux, Tumbleweed | Leave a Comment »

LD_PRELOAD: preload a Linux library, for instance to obtain more information on a segmentation fault

Posted by jpluimers on 2020/06/11

Not being a proficient Linux programmer, I wondered what other means than learning gdb intrinsics I had to get more information about a segmentation fault.

A while back, pip list 2> /dev/null would cause a segmentation fault on my system (see [WayBack] Bug 1084812 – [aarch64] IPv4 DNS leading to segfaults).

It turns out that LD_PRELOAD was my friend (like TERM=xterm was a friend before):

LD_PRELOAD=libSegFault.so pip list 2> /dev/null

It indicated that the problem was in libc, which on opensuse is implemented by glibc.

This meant that the originally diagnosed problem was already accurately describing the symptoms.

Searching for glibc libSegFault.so didn’t reveal many useful links, so I’ve included the one making most sense to me here:

The cool thing: most of the links above come from [WayBack] segmentation fault – Can you get any program in Linux to print a stack trace if it segfaults? – Server Fault which I found when searching for linux find segmentation fault stack trace

That link explains both the LD_PRELOAD steps and gdb steps (:

An alternative is to use gdb directly: [WayBack] command line arguments – How do I run a program with commandline args using gdb within a bash script? – Stack Overflow:

gdb -ex=run --args pip list

--jeroen

Posted in *nix, C, Development, gcc, Linux, Power User, Software Development | Leave a Comment »

Remote Desktop Auto Login Powershell Script · GitHub

Posted by jpluimers on 2020/05/29

Interesting: some PowerShell scripts that pipe a user and password through cmdkey.exe /generic:TERMSRV/$Computer /user:$User /pass:$Pass

–jeroen

Posted in *nix, Development, Linux, Power User, Software Development | Leave a Comment »

Best android apps for zabbix – AndroidMeta

Posted by jpluimers on 2020/05/28

If I land a project using Zabbix again, one of the things I need to look into is [WayBack] Best android apps for zabbix – AndroidMeta.

–jeroen

Posted in *nix, Android, Android Devices, Development, Linux, Mobile Development, Monitoring, Power User, Zabbix | Leave a Comment »

Raspberry Pi 1B OpenSuSE Tumbleweed zypper upgrade problem · GitHub

Posted by jpluimers on 2020/05/25

It looks like OpenSuSE has stopped supporting Raspberry Pi 1, so the best likely is to recycle it into a Pi-Hole as basically it’s been dead since mid 2017: [WayBack] Raspberry Pi 1B OpenSuSE Tumbleweed zypper upgrade problem · GitHub.

Build status for armv6l support: [WayBack] Project openSUSE:Factory:ARM Status Monitor – openSUSE Build Service

–jeroen

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Posted in *nix, *nix-tools, Debian, Development, Hardware Development, History, Linux, openSuSE, Power User, Raspberry Pi, Raspbian, SuSE Linux, Tumbleweed | Leave a Comment »

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