SamsiFPV

Building a Linux Distro with Yocto for the Variscite MX7

Thu, 19 Dec 2024 21:13:45 +0200

This guide is based heavily on the official guide from Variscite, with some additional info i found useful while learning this.

1 Dependencies

1.1 Ubuntu 16.04 LTS & 18.04 LTS

This tutorial was made with a machine running Ubuntu 18.04 LTS 64-bit, which worked almost flawless, though Variscite’s original tutorial is based on Ubuntu 16.04 64-bit.

sudo apt-get install gawk wget git diffstat unzip texinfo gcc-multilib \
build-essential chrpath socat cpio python python3 python3-pip python3-pexpect \
xz-utils debianutils iputils-ping libsdl1.2-dev xterm

sudo apt-get install autoconf libtool libglib2.0-dev libarchive-dev python-git \
sed cvs subversion coreutils texi2html docbook-utils python-pysqlite2 \
help2man make gcc g++ desktop-file-utils libgl1-mesa-dev libglu1-mesa-dev \
mercurial automake groff curl lzop asciidoc u-boot-tools dos2unix mtd-utils pv \
libncurses5 libncurses5-dev libncursesw5-dev libelf-dev zlib1g-dev

1.2 Ubuntu 20.04 LTS

Compiling Yocto thud does not work on Ubuntu 20.04 LTS 64-bit. The GNU C library, or short glibc, is version 2.30 in Ubuntu 20.04, which is incompatible to glibc 2.29, which the bitbake command expects. This patch from OCtober 2019 in the OpenEmbedded Core Layer fixes this, but it hasn’t been implemented into the Variscite BSP for Yocto thud. The last update for the thud-fslc-4.14.78-mx7-v1.0 tag was in May 2019, so it probably won’t be updated anymore. Downgrading the glibc is not recommended, so you should compile it in a virtual machine or with docker.

Common DNS Entry Types

Thu, 19 Dec 2024 21:13:45 +0200

Type: A

Point subdomain.domain.com to a hard coded IP Address. Most direct and straight forward option, also note any change you make in your DNS program is reflected on the internet and made live immediately. The only way you will not see immediate results is if you have cached a query on your computer by looking it up PRIOR to configuring it in your DNS program.

Type: MX

Point subdomain.domain.com to a mail server. These type of records are special for just mail servers, they can co-exist with A records, and their only use is for routing mail to a different location. All mail implementations check for this record first before attempting to route an e-mail message. If a MX record does not exist for a host, an e-mail delivery would be attempted directly to the IP that the hostname resolves to.

Detect compression type of a file

Thu, 19 Dec 2024 21:13:45 +0200

Use the file command first to get info about the possible compression. A tar archive has the filenames included in it at the top. You can determine that it is likely to be one of those formats by looking at the first few bytes. You should then test to see if it really is one of those, using an integrity check from the associated utility for that format, or by actually proceeding to decompress.

Give password-less sudo to a user

Thu, 19 Dec 2024 21:13:45 +0200

Edit the sudoers file

sudo visudo
# or
vim /etc/sudoers

After the entry #includedir /etc/sudoers.d add this:

<username>	ALL=(ALL) NOPASSWD: ALL

Save and exit, and you’re good to go!

How to add a Speaker via i2s and enable it in Yocto

Thu, 19 Dec 2024 21:13:45 +0200

Base for this project is the Variscite VAR-SOM-MX7 together with its development board.

Goal of this project is to get a speaker running over i2s on an embedded Linux system, and get a deeper understanding of the linux environment in general.

First steps

This guide assumes you already successfully compiled Yocto and have basic knowledge of navigating through an linux environment.

There are 2 things needed for this whole thing to work. First, Linux needs the driver for the Speaker/Microphone installed and loaded, so it can communicate with it. Second it needs to know where the Hardware is mapped to.

How to run Windows 11 in GNOME Boxes (with UEFI and TPM2 emulation)

Thu, 19 Dec 2024 21:13:45 +0200

Windows 11 significantly raised its hardware requirements compared to Windows 10. Among the changes, it requires more RAM and storage space. It also requires a Trusted Platform Module (TPM) version 2.0 and a UEFI boot environment.

GNOME Boxes doesn’t yet support TPM and UEFI environments. However, the underlying virtualization technology supports it. You just need to tweak a few configuration options along the way. Read the instructions carefully!

Install GNOME Boxes and its prerequisites

Start by installing GNOME Boxes from your Linux distribution’s package repository. You cannot use the Flatpak/Flathub version as it doesn’t currently support emulating a TPM. The package is called gnome-boxes everywhere. You need version 40 or newer!

Install Linux on an old Macbook

Thu, 19 Dec 2024 21:13:45 +0200

The Macbook I used: Macbook 13 Mid 2010

Nvidia driver solution:
https://askubuntu.com/questions/264247/proprietary-nvidia-drivers-with-efi-on-mac-to-prevent-overheating/613573#613573

Monitor brightness:
https://askubuntu.com/questions/76081/brightness-not-working-after-installing-nvidia-driver

Nvidia driver:
https://medium.com/@nolanmudge/installing-an-nvidia-graphics-driver-with-a-ubuntu-14-04-and-up-efi-boot-52725dd6927c

Wifi: firmware-b43-installer

Fan: maxfanctld

Power management: powertop, tlp

Wifi scanning: just set home network in /etc/wpa_supplicant/wpa_supplicant.conf like this:

Network={\nssid=\"ssid\"\npsk=\"pw\"\n}

Backlightbrightness: xbacklight, and custom shortcuts like that:

custom shortcuts:
https://askubuntu.com/questions/69114/how-do-i-logout-using-only-the-keyboard/69161#69161\nxbacklight: https://askubuntu.com/questions/354488/how-to-execute-command-with-keys\n",

Markdown Cheatsheet

Thu, 19 Dec 2024 21:13:45 +0200

Headers

# H1
## H2
### H3
#### H4
##### H5
###### H6

H1

H2

H3

H4

H5

H6

Emphasis

Italics: *asterisks* or _underscores_  
Bold: **asterisks** or __underscores__  
Combined: **asterisks** and _underscores_  
Strikethrough: two tildes. ~~Scratch this~~  
Underline: <ins>underline<ins/>

Italics: asterisks or underscores
Bold: asterisks or underscores
Combined: asterisks and underscores
Strikethrough: two tildes. ~~Scratch this~~
Underline: underline

Lists

1. First ordered list item
2. Another item
	* Unordered sub-list. 
1. Actual numbers don't matter, just that it's a number
	1. Ordered sub-list
2. And another item.

	You can have properly indented paragraphs within list items. Notice the blank line above, and the leading spaces (at least one, but we'll use three here to also align the raw Markdown).

	To have a line break without a paragraph, you will need to use two trailing spaces.  
	Note that this line is separate, but within the same paragraph.  
	(This is contrary to the typical GFM line break behaviour, where trailing spaces are not required.)

* Unordered list can use asterisks
- Or minuses
+ Or pluses

First ordered list item

OSI-Model

Thu, 19 Dec 2024 21:13:45 +0200

1 Physical - data cables 2 Data - Switching, MAC addresses 3 Network - IP addresses, routing 4 Transport - TCP/UDP 5 Session - Session management 6 Presentation - WMV, JPEG, MOV 7 Application - HTTP, SMTP

Please do not throw sausage pizza away

Over The Wire Wargames Solutions

Thu, 19 Dec 2024 21:13:45 +0200

Bandit Passwords

PW for bandit4: pIwrPrtPN36QITSp3EQaw936yaFoFgAB bandit5: koReBOKuIDDepwhWk7jZC0RTdopnAYKh bandit6: DXjZPULLxYr17uwoI01bNLQbtFemEgo7 bandit7: HKBPTKQnIay4Fw76bEy8PVxKEDQRKTzs bandit8: cvX2JJa4CFALtqS87jk27qwqGhBM9plV bandit9: UsvVyFSfZZWbi6wgC7dAFyFuR6jQQUhR bandit10:truKLdjsbJ5g7yyJ2X2R0o3a5HQJFuLk bandit11:IFukwKGsFW8MOq3IRFqrxE1hxTNEbUPR bandit12:5Te8Y4drgCRfCx8ugdwuEX8KFC6k2EUu bandit13:8ZjyCRiBWFYkneahHwxCv3wb2a1ORpYL bandit14:4wcYUJFw0k0XLShlDzztnTBHiqxU3b3e bandit15:BfMYroe26WYalil77FoDi9qh59eK5xNr

PDF-Tools

Thu, 19 Dec 2024 21:13:45 +0200

PDF arranger

Can make booklets. Arrange, delete, add pages to pdfs.

pdfbook

Use pdfbook2 from texlive-extra-utils to create a booklet.

pdfjam

If some pdf program complains about different sized pages, use pdfjam to make them all the same size

pdfjam --outfile out.pdf --paper a5paper in.pdf

Jpdf Tweak

Swiss army knife for pdfs. Watermarks, page numbering, bookmarks, attachments, document info, encryption, etc.

OCRmyPDF

OCR on images and pdfs.

ocrmypdf no_ocr.pdf ocr.pdf --sidecar ocr.txt -l deu+eng --force-ocr

If –force-ocr is issued, then all pages will be rasterized to images, discarding any hidden OCR text, rasterizing any printable text, and flattening form fields or interactive objects into their visual representation. This is useful for redoing OCR, for fixing OCR text with a damaged character map (text is selectable but not searchable), and destroying redacted information.

Shrinking .img files on Linux

Thu, 19 Dec 2024 21:13:45 +0200

Context of the problem:

Having a myimage.img bigger then the hardware support (if it is smaller there should be no problem; however, using the same strategy, you can better fit the image in the hardware support).

The secret is to use standard Linux tools and instruments: GParted, fdisk and truncate.

Requirements:

A Linux PC
The .img you want to shrink (myimage.img in this example)

Creating loopback device:

GParted is an application typically used to manage partition tables and filesystems. In order to shrink the image, GParted is going to be used along the first part of the answer.

Systemd targets

Thu, 19 Dec 2024 21:13:45 +0200

Target	Description
halt	Shut down all services and halt the system
poweroff	Shut down all services and power off the system
shutdown	Shut down the system normally
rescue	Single-user (root) mode for maintenance and recovery functions. It mounts all file-system but does not start any networking related service or function.
multi-user	Multi-user command line mode for regular tasks. It starts all essential and custom services and provides the CLI prompt for login and work.
graphical	Same as the multi-user.target but also includes GUI. A user can use the graphical desktop environment to login and work or can use regular command line interface.
reboot	Reboot the system normally.
default	Default target to boot the system. Usually set either to multi-user.target or graphical.target.
emergency	Start an emergency shell and mount only root file-system. Other file-system and networking remain disabled.
hibernate	Save the running state of the system to the hard disk and power off the system. When the system is power on again, the systemd restores the saved state.
suspend	Same as the hibernate except the system state is saved in the memory and power to the memory is not turned off.

Useful Linux commands and applications

Thu, 19 Dec 2024 21:13:45 +0200

Commands (May not be preinstalled on your distro)

gdu - disk usage in go with multiprocessor (alternative: ncdu)
fd - better find
wavemon - analyse wifi
pv and progress - watch progress of a command
hardinfo - hardwareinfo
sshfs - mount remote servers

Crop multiple fotos

for i in *.png; do convert -crop aaaxbbb+ccc+ddd "$i" out/"$i"; done

Where:

aaa is the x offset from the left
bbb is the y offset from the right
ccc is the horizontal size of the output image
ddd is the vertical size of the output image

All in pixels, you can get them by selecting just one image in gimp and looking at the bottom bar for the values ;)

Common GCC Attributes

Tue, 13 Aug 2024 21:13:45 +0200

Function attributes

fallthrough

The fallthrough attribute with a null statement serves as a fallthrough statement. It hints to the compiler that a statement that falls through to another case label, or user-defined label in a switch statement is intentional and thus the -Wimplicit-fallthrough warning must not trigger.

For compatibility with GCC and Clang you can also use // fall through or // fallthrough.

switch(cond)
{
case 1:
  bar(1);
    __attribute__((fallthrough));
  case 2:
    …
}

deprecated & deprecated (msg)

The deprecated attribute results in a warning if the function is used anywhere in the source file. This is useful when identifying functions that are expected to be removed in a future version of a program. The warning also includes the location of the declaration of the deprecated function, to enable users to easily find further information about why the function is deprecated, or what they should do instead.

What is the difference between `char a[]` and `char *p`

Wed, 28 Feb 2024 21:24:23 +0200

The Array version:

char a[] = "string";

Creates an array that is large enough to hold the string literal string, including its NULL terminator. The array string is initialized with the string literal string. The array can be modified at a later time. Also, the array’s size is known even at compile time, so sizeof operator can be used to determine its size.

The pointer version:

char *p  = "string";

Creates a pointer to point to a string literal “string”. This is faster than the array version, but string pointed by the pointer should not be changed, because it is located in a read only implementation-defined memory. Modifying such an string literal results in Undefined Behavior.