Managing and Troubleshooting File and Directory Permissions in Linux
Linux Training Architect I in Content
The interactions among the different permission schemes in Linux can be a little bit of a "magic cloud" to some. This course aims to alleviate some of that confusion, and gives tips on how to troubleshoot permission errors that are commonly seen. We'll cover "normal" (octal) permissions, ACLs, SELinux configurations, and some other special permission settings that aren't as commonly used.
Welcome to Managing and Troubleshooting File and Directory Permissions. This video will have a quick overview of what we're going to talk about and then I'll introduce myself.
Understanding Octal Permissions in Linux
What are Octal Permissions?
To understand how to manage and troubleshoot permissions, we first need to make sure we understand the baseline of permissions. Octal permissions are what we see every day with commands like
chmod. This lesson will give a lot of information on what they are and how to manipulate them, in addition to some information on troubleshooting.
User Permissions vs. Group Permissions
When discussing permissions, it's useful to know about and have examples of what the differences between user and group permissions are. Seeing some examples of issues that can come up if permissions are incorrect is also handy.
When discussing permissions in Linux, it's always useful to know where we started from. Default permissions are fine, but how do we customize those without having to change every file after creation? The
umaskcommand will help with that, and in this lesson we learn how.
Permissions on Links
Symlinks and hard links are both very useful, and can also create issues while troubleshooting. This lesson will demystify some of the confusion surrounding links and how permissions work with them.
Special Interactions Based on the `root` User
root user is powerful, but using it to troubleshoot permission issues can cause trouble, because of the all-powerful access that UID 0 bestows. This lessons goes through some of those issues and shows how they can come up, and also shows a method to run a shell as a "special" user like
apache to assist in troubleshooting.
Linux Access Control Lists
Working with `getfacl` and `setfacl`
Linux Access Control Lists (ACLs) are an amazing tool we can use to supplement octal permissions. This lesson goes through what ACLs are, how to check the current settings, and some common pitfalls when using them.
Understanding the Interaction between ACLs and Octal Permissions
Understanding the interactions between ACLs and octal permissions is important. It's a good skill to have when troubleshooting permission issues where ACLs may be involved. This lesson goes over some more interactions, including when
root tries to access ACL protected files.
Understanding SELinux Labels
One of the most referenced challenges when it comes to permission issues is SELinux. Many administrators just set it to Permissive or Disabled so it doesn't get in the way. However, learning a few different things would allow them to run it as Enabled and have a more secure system overall. This lesson covers SELinux labels and contexts.
Understanding SELinux Booleans
SELinux Booleans control how processes can access files on a Linux system, so understanding how to manipulate them and what to look for is an important skill for Linux Administrators. This lesson covers that and walks through an example with
Interactions Among Different Permission Schemes
When looking at different permission schemes it's important to understand how they interact to determine how best to secure a file. This lesson covers the interactions between SELinux and octal/ACL permissions.
What are Special Bits?
Special bits are permission bits set using octal permissions that manipulate how the kernel interacts with the file. Some of them change what user or group a process runs as, while another changes how users can interact with files inside a directory. This lesson goes over them.
Outside of file and directory permissions, there's another way to manipulate how the kernel interacts with a file. Special attributes can manipulate how a file is stored, among other things. This lesson goes over how to manipulate those attributes.
Welcome to the end of the course! In this video we'll wrap things up and go over what we've learned.
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