Introduction

I keep some notes here, mostly development related things, as well as "quick ref"-guides on Linux commands and similar things.

Note: This book contains public notes only. My private notes are kept elsewhere.

The source code from which this book is generated is available on github.com/christianfosli/notes.

Bash / Linux / GNU tools quick ref

Terminal Signals :stop_sign:

• Exit Ctrl-D

• Cancel (kill) app/job Ctrl-C

• Suspend Ctrl-Z suspend (pause) an app/job (go back to bash)

  • Resume job fg (list all with jobs)

Readline :ledger:

• Go to beginning of line Ctrl-a

• Go to end of line Ctrl-e

• Delete line Ctrl-x <Backspace>

• Move by words Ctrl- <Arrow-Keys>

• Open command in $EDITOR, execute upon exit Ctrl-x Ctrl-e or fc

Files and Directories :file_folder:

• Copy file contents to clipboard (on WSL) cat $file | clip.exe

• Copy file contents to clipboard (on Wayland) cat $file | wl-copy

• Search command history: <C-r> startOfCommand

• Search for "pattern" and print matching lines: grep. Hint: ripgrep rg is easier to use and super fast.

• Find files by filename: find . -name Foo.txt.

  • Find files case insensitive filename: find . -iname "*foo*txt"

  • Or use a fuzzy finder (fzf/skim/neovim telescope).

• Create symlink ln -s actual_file_path symlink_path

• Extract .tar.gz file tar -xzf <filename (remember eXtract tZe File)

Networking :globe_with_meridians:

• List ip-address ip addr

• List ip addresses on same network: ip neigh

• nslookup

• SSH ssh username@ip -p portnumber

  • Start ssh service to allow log-ins (fedora) systemctl start sshd.service

• Copy files between local computer and remote scp $file username@ip:/home/$dir or scp username@ip:/home/$file $localdir

tmux :computer:

• list sessions tmux ls or Ctrl-b s

• attach tmux attach #

• rename window Ctrl-b ,

• new pane Ctrl-b " or Ctrl-b %

• break out pane to a new window Ctrl-b !

• toggle layouts Ctrl-b <space>

• resize pane Ctrl-b :resize-pane -{L|R|D|U} {cellSize}. Can also be done from the shell:

  $ tmux resize-pane -R 10
  

• resize panes Ctrl-b alt-arrows

• popup tmux display-popup [-E 'python']

Gnome :framed_picture:

• Activities overview: <super>

• Move focus to menubar: <super> <f10>

• Move focus between window and menubar: <control> <alt> <tab>

• Switch between windows: <super> <tab>

  • Then press ` or <down> to switch through windows within an application

• Switch between workspaces: <super> <alt> <arrow>

• Snap window: <super> <arrow-keys>

• Move window to another screen: <shift> <super> <arrow-keys>

• Pop open window menu: <alt> <space>

• Focus on active notification: <super> n

• Show notification list: <super> v

• Send notification from terminal:

  $ notify-send 'Hello world' 'the command has finished'
  

• Lock screen: <super> l

• Screenshot...: <PrintScreen>

• Project external displays: <super> P

• Toggle zoom: <alt> <super> 8

• Emoji picker: <windows> <.> <keyword> <space> <space>

  • Note: Does not work in all applications. E.g. Currently doesn't work in Chrome.

alacritty :keyboard:

• Launch vi mode: Ctrl Shift Space

systemctl & UEFI/BIOS :control_knobs:

• Boot into UEFI/BIOS: sudo systemctl reboot --firmware-setup

• See boot order sudo efibootmgr

• Boot next sudo efibootmgr --bootnext XXXX

Configure systemd-resolved to not use azure private endpoints

• Create file /etc/systemd/resolved.conf.d/az_blob_pub.conf with the following content

  # Work around missconfigured peerings from on-prem networks to azure blob storage private endpoints
  # by forcing DNS to a public DNS server (in this case cloudflare DNS)
  [Resolve]
  DNS=1.1.1.1 2606:4700:4700::1111
  Domains=~blob.core.windows.net
  

Good to know cURL options

• Download to file using filename from URL: -O | --remote-name

• Silent: -s | --silent. Don't show the progress bar.

• Follow redirects: -L | --location

• Retries: --retry <n>

• Fail silently on HTTP errors / bad status codes: -f | --fail

• Include response headers in output: -i | --include

• Username/password: -u username:pass

• Client certs: --cert cert-w-key.pem:password or --cert cert.crt --key key.key

• Allow insecure TLS connections (i.e. untrusted certs): -k | --insecure

• STDIN as body: -d@-. E.g. cat f.json | curl -H "Content-Type: application/json" -d @- http://api

• json (curl >= 7.82): jo name=christian tool=curl | curl --json @- http://api | jq

• Override dns resolve: curl https://domain.example --connect-to domain.example:443:203.0.113.81:443

Docker quick ref :whale:

• Most used commands: docker ps, docker images, docker build, docker run

• Most used docker-run flags: -it interactive terminal, -d detached (in the background)

• Detach from running container: Ctrl P Q

• Remove all non-running images: docker rmi $(docker ps -aq) or docker image prune -a

• Check disk usage: docker system df

• Exec as specific user: docker exec -u root -it <containername>

• Run container with the same network namespace as another: docker run -it --network container:<containername> alpine

.NET Quick-Ref

• run xunit tests with output to console: dotnet test --logger "console;verbosity=detailed" --filter <filterexpr>

  • <filterexpr> can be e.g. the test name, or with XUnit.Categories e.g. Feature=83922. But if we are interested in the output then it's best to run one test at a time, otherwise it's hard to find.

• run fsharp fsx script dotnet fsi <filename>

• open fsharp interpreter dotnet fsi --readline

Fixes and work-arounds

• Strings.PlatformNotSupported_DataSqlClient error when running ef core database migrations on (some) linux platforms

  • Add --runtime linux-x64 to the cli command

• Microsoft.Data.SqlClient.SqlException when connecting to database over HTTPS on older versions of dotnet core with newer versions of OpenSSL

  Microsoft.Data.SqlClient.SqlException (0x80131904): A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: TCP Provider, error: 35 - An internal exception was caught)
  ...
   ---> System.TypeInitializationException: The type initializer for 'SslInitializer' threw an exception.
   ---> Interop+Crypto+OpenSslCryptographicException: error:0E076071:configuration file routines:module_run:unknown module name
  

  • Set environment variable OPENSSL_CONF=/dev/null before/while running your command Source: https://stackoverflow.com/questions/73004195/phantomjs-wont-install-autoconfiguration-error

Git quick-ref :tanabata_tree:

Open help-page: git help command

• Everyday work

  • Check what's up git status

  • See what happened git log [--graph --date=human --stat])

    • one-line commits: git log [--graph] --oneline

    • show the patch: git log [--graph] -p

  • Add files to stage git add filename

    • Stage part of file git add -p filename

  • Unstage file git restore --staged <filename>

  • Check diff git diff branch1 branch2 or file1 file2 etc

    • Check message and diff of commit: git show <commit-hash>

      • Include commit (as well as author) date: git show --format=fuller <commit-hash>

    • Check diff for a merge commit:

      • Given this commit:

      commit ccc333
      Merge: aaa111 bbb222 
      

      git diff aaa111...bbb222
      

    • Exclude specific file from diff: git diff -- . ':!package-lock.json' or git show HEAD -- . ':!Cargo.lock'

  • Commit stage to current branch git commit

    • Commit all tracked files with changes: git commit -a

    • Use interactive patch selection to decide what to commit: git commit -p

    • Show diff below the commit message: git commit -v

  • Restore file to HEAD git restore <filename>

  • Restore file to branch git restore -s <branchname> <filename>

• Misc

  • Does origin/master have new commits? (commits not reachable from HEAD)

    git fetch origin && git log ..origin/master

  • Ignore future local changes to a tracked file (useful for config files...) git update-index --skip-worktree <filename>

    • Undo with git update-index --no-skip-worktree <filename>

  • Apply patch (3-way merge)

    git show <sha1> | git apply -3

• Branches

  • Show branches git branch or git branch -vv or git branch -r

  • Create branch git branch <branch-name>

  • Switch to branch git switch <branch>

  • Do both 2 above git switch -c <branch name>

  • Merge/rebase branch first checkout the to-branch then git merge <from-branch> or git rebase <from-branch>

  • Delete branch git branch -d <branch> force delete with git branch -D <branch>

  • Delete every branch except master git branch | grep -v "master" | xargs git branch -D

  • Reset branch to earlier commit / branch / tag git reset --hard <commit>

  • Clean up latest n commits (opens interactive rebase editor letting you squash, pick, fixup, reorder)

    git rebase -i HEAD~n

  • Rebase and update intermediate "feature branches" git rebase --update-refs

• Remotes

  • Fetch latest changes git fetch <remote>

    • And remove remote remote tracking branches which have been deleted git fetch -p <remote> (shows [gone] on git branch -v)

  • Show remote info git remote -v or more info with git remote show <remote>

  • Fetch and merge git pull

  • Push to remote git push <remote> <branch> [--force-with-lease]

  • Push and add upstream (tracking) reference git push -u <remote> <branch>

  • Delete remote branch git push <remote> -d <branch>

  • Update submodules git submodule update or git submodule update --remote

• Finding commits

  • Search by author: git log --author <name>

  • Search by commit message: git log --grep <regexp>

  • Search by patch text (i.e. diff content): git log -G <regexp>

GitHub tips and tricks

• Clear cache, if using GitHub Actions cache (e.g. for docker build): gh cache delete --all --repo {org}/{repo}

Notes about TLS, PKI, certs and keys.

Everything you should know about certificates and PKI but are too afraid to ask

Good read 😊 by SmallStep

https://smallstep.com/blog/everything-pki/

Fun facts

PEM stands for Privacy Enhanced Email. It was originally developed to encrypt emails. It never cought on, though, and the related RFC's were eventually obsoleted by PGP and S/MIME.

Step CLI

Similar to openssl but with better UX. https://github.com/smallstep/cli

ssh-rsa

• Deprecated by OpenSSL

  It is now possible[1] to perform chosen-prefix attacks against the SHA-1 algorithm for less than USD$50K. For this reason, we will be disabling the "ssh-rsa" public key signature algorithm by default in a near-future release.

• Blocked in Fedora Linux 33

• Solution: Switch SSH keys to Eliptic Curve ed25519

  • Problem: Azure DevOps only supports legacy ssh-rsa Round 2

EC cryptography for dummies

https://blog.boot.dev/cryptography/elliptic-curve-cryptography/

Microsoft 365 related notes

MS Teams keyboard shortcuts

• Focus on search field: Ctrl-E

• Focus on search field for command: Ctrl-/

• Switch chats: Alt-

• Switch sidebar tabs: Ctrl-1/2/3/4.. (web Ctrl-Shift-1/2/3/4..)

• Keyboard driven chat: Switch focus with <up> and <down>, enter reaction menu with <enter>

Work-arounds / hacks

• Workaround to fix Microsoft Edge based Web Apps not having there own icon when Wayland is enabled

Misc

• Update Microsoft Defender policies/definitions on Linux: mdatp definitions update

• Check Microsoft Defender health: mdatp health

Python Quick-Ref

Managing python versions, environments and dependencies

Use uv!

"uv-first" projects

• Initialize new project

  uv init {project_name}
  

• Initialize existing project and install deps

  uv sync
  

• Install and update existing deps

  uv sync --upgrade
  

• Add dep

  uv add {dep}[version_constraint]
  

• Remove dep

  uv remove {dep}
  

• Upgrade dep

  uv lock --upgrade-package {dep}
  

uv-first scripts

uv add --script example.py pandas  # Legger til kommentar på toppen av filen
uv run example.py

Debugging and troubleshooting

• Debugging pandas dataframes and series, plot pd.Series:

  breakpoint()  # Stop execution and enter debugger. Enter the remaining into debug console at the right time
  import matplotlib.pyplot as plt
  df.plot()
  plt.show()  # plot appears
  

Convenient cli's

• Generate a uuid: python -m uuid

• Serve static files in current directory: python -m http.server 8000

Logging in pytest output

pytest -o log_cli=true --log-level=DEBUG

or persistant in a config file, which by convention resides in the root directory of the repository

# pytest.ini
log_cli=true
log_level=DEBUG

# pyproject.toml
[tool.pytest.ini_options]
log_cli="true"
log_level="DEBUG"

ref pytest docs

Ruff

• Format: ruff format {file|dir}

• Lint: ruff check [--fix] {file|dir}

• Organize imports: ruff check --fix --select I or add to pyproject.toml:

  [tool.ruff.lint]
  extend-select = ["I"]
  

• Example config:

  [tool.ruff]
  line-length = 120
  
  [tool.ruff.lint]
  extend-select = ["I"]
  
  [tool.ruff.lint.isort]
  known-first-party = ["myorg_*"]
  

BasedPyright

A fork of the Pyright LSP with various feature improvements, such as code action for missing imports!

Works nicely with terminal editors like Helix.

See https://docs.basedpyright.com/latest/

Interesting Python / JS Interop project

PythonMonkey Kode24 Article

Vim favorite commands / built in stuff

• CTRL-] or gd - Jump to definition

• CTRL-O Jump back

• CTRL-I Jump forward

• K show definition of keyword

• f {char} - go to first occurance of char

• t {char} - go just before first occurance of char

Helix (move me somewhere?)

• Due to some intelligent(ish) workspace root detection looking for .git folder, make sure to open deno files from the correct folder.

Web related notes

Chromium features to follow :eyes:

• Shared element transitions: Polished transitions/animations when navigating between pages in web applications.

  • Trial in Chrome 104-106

  • Explainer

• Multi-Screen window placement: Allow web applications to offer compelling multi-screen experiences.

  • Chrome Feature

  • Info

  • Expainer

Chrome & Web news

• https://web.dev

  • Check https://web.dev/learn for tutorials :smile: e.g. https://web.dev/learn/pwa/ to learn about progressive web apps

"New" HTML elements

• <dialog> mdn

WebAuthn

Web authentication using public key cryptography instead of passwords

• Guide

FedCM

Federated credential management without needing third-party cookies.

• Blog post

Patterns

Check patterns.dev