Some handy Raspberry Pi stuff ;)

Datasheets/Schematics

https://datasheets.raspberrypi.com/

Questionning the USB 'roles' & whre/how it connects:

• schematic for USB interface question: https://forums.raspberrypi.com/viewtopic.php?t=217858
• https://raspberrypi.stackexchange.com/questions/127415/are-schematics-available-for-the-newer-rpi-4-with-fixed-usb-c-power-circuit

Pinouts

Model A and B (Original)	Model A+, B+ and B2

install OS image on SD card

• run df -h to see the devices currently mounted
  ex of output:

  Filesystem      Size  Used Avail Use% Mounted on
  # ( .. )
  /dev/mmcblk0p1   32G   32K   32G   1% /media/stephaneag/F0E9-334E

• the device name 'll be the 'Filesystem' name minus the partition number
  ex: for '/dev/mmcblk0p1' it'll be '/dev/mmcblk0', for '/dev/sdd1', '/dev/sdd'

• to only list the connected SD cards ( if they use the standard naming system ), run:
  df -h | head -1; df -h | grep 'mmcblk\|sdd' | cat

• unmount any partition related to the SD card using unmount /dev/<SC_card_filesys><partition>
  ex, for the first partition of '/dev/mmcblk0p1':
  'unmount /dev/mmcblk0p1'

• write the .img to the SD card using dd bs=4M if=<img> of=/dev/<SC_card_filesys>
  ex, for a Raspbian release:
  dd bs=4M if=2015-09-24-raspbian-jessie.img of=/dev/mmcblk0

• to see some progress about the operation, as dd doesn't giv any, we can use the following:

  • to get an update on the progress: sudo pkill -USR1 -n -x dd
  • to get updates on the progress: watch -n5 'sudo kill -USR1 $(pgrep ^dd)'
  • other ways to do so ( pv, dcfldd): Ask Ubuntu - monitor the progress of dd

Bypass/replace a lost password

Nb: this should also work for ANY linux system ;)

• plug the SD card containing the RPi system on a laptop, & open the /etc/shadow file for editing

• in it, find the line that has the following syntax and correct username: '<username>:<hashed_password>:::'
  ex of what the line should look like:
  'pi:$6$3YkhpIdG$y4C5gTMdnVnhMND9Pe.MFRi3Gi.. ..zTz52bnG1XOcXuhNOpk85xQJfQ.:15710:0:99999:7:::'

• replace it with either:

  • another <username>:<hashed_password>::: line
  • an empty password for the same user, using <username>::::, ex: pi::::

• on the next boot of the RPi, no password 'll be asked ( if we set an empty password ) !
  we could also set a new password if we left it empty, using passwd <username> as in the following:

  passwd pi
  <new_password>
  <new_password_again>