In Linux user management access works just like it does in Windows, different user types have different privileges and they can be grouped together with various access levels. There are a few differences in how Linux does labeling, though. There are standard users, and there are also administrators in Linux, and there's also a special user called the Root User. Don't get this confused with the root directory or slash, the Root User is the first user that gets automatically created when we install a Linux OS. This user has all the privileges on the OS, they're the super user. There's technically only one super user or root account, but anyone that's granted access to use their powers can be called a super user too. Now, let's try and view the contents of a route restricted file. The file path is etc/sudoers, we're getting an error, cat/etc/sudoers: permission denied. The sudoers file is a protected file that can only be read by root. We can log in as root and then run this command, no problem. But it can be really dangerous to always be in root. Since root, like our local administrator account on Windows, has unrestricted access on the machine. If we make even one mistake, we could delete or modify something important, then that's not good. So instead of logging in its root, we can tell the shell that we want to run this one command as root. Sounds similar to the Windows UAC feature, that's because it is, on Linux we can do this with the sudo command, or superuser do. So sudo cat/etc/ sudoers and now we're able to see the contents of this file. If you don't want to run sudo every time you need to run a command that requires root privileges, you can just use the su command or substitute user. This will allow you to change to a different user, if you don't specify user, it defaults to root. Now you can see my prompt says root@cindy-ncy. Again it's generally not a good guideline to stay logged in as root all the time. There are lots of critical services and files that can be mistakenly changed. If you need to log in as root, it's okay but just be careful. I'm just going to go ahead and exit out of root for now and go back to my normal user. You can view who has access to run sudo by viewing the /etc/groupfile. This is also how you view memberships for all groups. This looks a bit different from the Windows gooey, but you can see there are some similarities to the Windows cli, it's actually pretty simple to read this file even if you're not a bash expert yet. Each line represents a different group. Let's look at the sudo line. There are four fields here, separated by colons, the first field is the group name. In this case, it's sudo, the second field is the group password. We don't really need to specify a group password, so it defaults to the root password. The x here means that the password has been encrypted, and stored in a separate file that we'll talk about in a later lesson. The third field is the ID of the group, or group ID. When our operating system runs a task that involves a group, it uses a group ID Instead of a group name. And finally, the last field is a list of users in the group. What if we wanted to view the users on our machine? What do you think the file would be that stores that information? Unfortunately, it's not /etc/user, the file that contains user information is /etc/password. Wow, there's a lot more information in here, and a lot more users. Most of these accounts aren't actually humans using the computer, there are a bunch of processes that are constantly running on a computer that we need to associate with the user. So our system has lots of users with different permissions that are needed to run these processes. Let's look at this first line here, which is an actual user, we can log into root. We won't talk about all the fields since they aren't important, but the first three are relevant. The first field is the user name, and the second field is the user password. The password isn't actually stored in this file, it's encrypted and stored in a different file. Just like our group ID password. The third field here is the user ID or UID. Similar to group IDs, user IDs or how our system identifies a user, not by the user name. Root has a UID of zero. And that's basically how you view users and groups in Linux
