Linux is a kernel. See https://xkcd.com/456/

TPM stuff

https://kernelnewbies.org/Linux_Kernel_Newbies is a good starting point for learning about the kernel.
https://kernelnewbies.org/Outreachyfirstpatch → Write your first patch for the kernel

https://man7.org/tlpi/ → The Linux Programming Interface – Michael Kerrisk

https://github.com/PacktPublishing/Linux-Device-Driver-Development-Second-Edition → Linux Device Driver Development, Second Ed. – John Madieu

fs/ → virtual file system implementation (generic fs code and toplevel implementation of fs syscalls), specific filesystems
mm/ → virtual memory management (mmap, kmalloc, vmalloc)
kernel/ → core kernel code, scheduler, primitives (printk), process syscalls (fork, exit)
net/ → network generic code and protocol implementations; most syscalls in net/socket.c

Interactive map of the Linux kernel

change xorg settings

xset s off Disable screen saver blanking
xset s 3600 3600 Change blank time to 1 hour
xset -dpms Turn off DPMS
xset s off -dpms Disable DPMS and prevent screen from blanking
xset dpms force off Turn off screen immediately
xset dpms force standby Standby screen
xset dpms force suspend Suspend screen

NOTE: This section is meant for tidbits of useful knowledge on linux, mostly commands.
Ideally, these notes will branch out over time, and I will refactor them into separate topics under Linux.

• On a systemd-based system you can restrict a process’s memory use with systemd-run --scope -p MemoryMax=500M --user program
• To open a port in Linux with iptables:

# allow TCP ipv4 
iptables -I INPUT -p tcp --dport 3389 -j ACCEPT
# allow UDP ipv4
iptables -I INPUT -p udp --dport 3389 -j ACCEPT
# allow TCP ipv6
ip6tables -I INPUT -p tcp --dport 3389 -j ACCEPT
# allow UDP ipv6
ip6tables -I INPUT -p udp --dport 3389 -j ACCEPT

• To add swapfile to Ubuntu 20 server:
  • sudo fallocate -l 1G /swapfile
  • sudo chmod 600 /swapfile
  • sudo mkswap /swapfile
  • sudo swapon /swapfile
  • Makes changes permanent: echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab
• Java:
  • apt-cache search openjdk to search for all available java packages.
  • update-alternatives --config java to select default java runtime
• To add a user sudo useradd -m username which will create user along with home directory.
• To list all users run cat /etc/passwd
• To type unicode symbols in Linux, hold CTRL+SHIFT+U, let go of all three, type the unicode code and press space.
• Generate a random password with tr -dc A-Za-z0-9_ < /dev/urandom | head -c 16 | xargs
• Enable promiscuous mode on network adapter (for network tools under a VM) with chmod a+rw /dev/vmnet0
• Run linux with bad memory (from pragmaticaddict)
  • Test with memtest86+
  • Use the memmap kernel option to mark the area as reserved
    • Example: memmap=0x121640a20$0x12410abb0
• Run command as system user: su - targetuser -s /bin/bash
• See keycodes easily with xev | awk -F'[ )]+' '/^KeyPress/ { a[NR+2] } NR in a { printf "%-3s %s\n", $5, $8 }'
• Parallelize with NUM_PROCS=$(cat /proc/cpuinfo | awk '/^processor/{print $3}'| wc -l)
< $@ xargs -d '\n' -P $NUM_PROCS -I {} /bin/bash -c "{}"
• View your webcam with mpv av://v4l2:/dev/video0 --profile=low-latency
• View speed of interface cat /sys/class/net/<interface>/speed
• Rename everything in cwd to lowercase for f in *[[:upper:]]*; do mv -- "$f" "${f,,}"; done

Configure default applications for xdg-* at ~/.config/mimeapps.list

• https://www.catb.org/~esr/writings/unix-koans/introduction.html → Unix teachings of the Master Foo
• https://linux-audit.com/about/ → linux articles, guides, security information
• https://beej.us/guide/
  • useful resources on unix & programming (sockets, C, GDB, …)
  • C guide
  • GDB

https://cb.vu/unixtoolbox.html

https://sergiu121.github.io/docs/index.html → USO lab book starter on operating systems and (mostly) linux
https://ocw.cs.pub.ro/courses/uso/cursuri/start → USO wiki, slides and resources

http://quotes.cat-v.org/programming/bumper-sticker-computer-science → 20/20 hindsight CS quotes
https://perl.plover.com/ → Lots of unix stuff: history, teachings, presentations on various topics.
https://djoffe.com/stuff/linuxref/ → useful linux CLI tools with description

https://blog.robertelder.org/linux-hardware-debugging/ → hardware debugging resource

https://0xax.gitbooks.io/linux-insides/content/ → kernel internals; work in progress book

https://github.com/mk-fg/fgtk → helpful public domain scripts

• https://lwn.net/headlines/rss → weekly linux news
• https://www.phoronix.com/ → frequent kernel updates