mtilson

Linux File Permission Cheat Sheet

• Necessary and sufficient knowledge on Linux file and directory permissions
• With practical examples
• Sourced from GitHub

User permission triads

• There are three permission triads (rwx rwx rwx) corresponding to particular group of users
• The 1-st one (rwx --- ---) is for owner user

mtilson

Linux makes a distinction between process and program executing

System calls

• exec()-like
  • related to program executing
  • load a new program
  • after the call the process resumes execution with a brand new address space containing the loaded program
• fork()
  • related to process executing
  • create a new process
• the process that invokes a fork() is the parent process

mtilson

Background

• Let's say we have two users (schacon and jessica) both having write access to the same GitHub repo

[user@pro13 schacon (master)]$ git log --oneline --all 
* 6c4e96c (HEAD -> master, origin/master, origin/HEAD) Initial commit

[user@pro13 schacon (master)]$ git remote -v
origin	https://github.com/txxxx-xx/xxx.git (fetch)
origin	https://github.com/txxxx-xx/xxx.git (push)

mtilson

• HEAD - pointer to the local branch you’re currently on (reference to the most recent commit in curent branch)
  • $ cat .git/HEAD

ref: refs/heads/master

• refs/remotes/origin/HEAD - is the same type of pointer as local HEAD, but for origin remote
  • all refs/remotes/origin/* are remote-tracking branches which are local references (to the state of remote branches) that you can’t move
    • Git moves them for you whenever you do any network communication, to make sure they accurately represent the state of the remote repository
    • think of them as bookmarks, to remind you where the branches in your remote repositories were the last time you connected to them
    • git fetch <remote-name> updates your remote-tracking branches

mtilson

All the details are based on [Git Remote Branches] unless otherwise stated

---

Sharing a Branch with the World

Create and push a branch on one workplace (WP), and fetch and check out the branch on another workplace

• Create and push on workplace 1

WP1> git branch fix
WP1> git checkout fix

mtilson

We have only one remote

• $ git remote

repo-to-fetch

Directory structure

• $ tree -L 1

.

mtilson

We have only one remote

• $ git remote

origin

Directory structure

• $ tree -L 1 .git

.git

mtilson

#!/usr/bin/env bash

# we are going to fetch all refs (including 'refs/pull/*') from Git remote
#   'repo-to-fetch', which points to public GitHub repo defined by URL
#   '${repoURL}' where the GitHub user account '${userName}' has write access
# for more details on GitHub 'refs/pull/*' refspecs see [1]

userName=mxxxxxx
[email protected]
repoURL=https://github.com/txxxx-xx/gxx-xxxx.git

mtilson

#!/usr/bin/env bash

# let's say we have GitHub 'org' with 'team' of 2 members 
#   ('member1', 'member2') having Write access to
#   'repo' with URL of 'https://github.com/org/repo.git' 

# we are going to setup repository and global Git options
#   (on macOS) to be able to commit to 'repo' using the  
#   above GitHub user accounts including different network 
#   authentication

mtilson

#!/usr/bin/env bash
set -e

# we are going to setup different GitHub Actions workflows on
#   GitHub repo '${repoName}' under GitHub user account '${userName}'
#   which has Write access to the repo

# to trigger 'webhook' event with help of 'curl' command we use
#   'Authorization' header with personal access token '${token}' which
#   has to be created aforehand, see [2]