When we were exploring the system in previous lectures, we may have encountered a problem when trying
to examine a file, for example, such as the shadow files, for example.
File.
And e.t.c. shadow.
And here, as you can see, regular file, no read permission and you can also here less.
We can also here shadow.
And as you can see here, the permission is denied.
So the reason for this error message is that as a regular users, we do not have permissions to read
this file.
In the Unix security model, a user may own files and directories.
So when a user owns a file or directory, the user has control over its access.
User can in turn belong to a group consisting of one or more users who are given access to files and
directories by their owners.
In addition to granting access to a group, an owner may also grant some set of access rights to everybody.
So when in which in Unix terms is referred as the world, so the find out information about your identity,
you can use the ID command.
And as you can see here in this case, in the output when user accounts are created, users are assigned
a number called ID, which is then for the sake of the humans mapped to as a username.
So the user assigned a group ID here GID and may belong to additional groups.
So this example is from our Kali system on other systems such as Fedora or Ubuntu, the output may look
different, so as we can see the user id.
And group the guide here.
Actually, let me write that down here.
So.
Some of you can also understand.
So user ID means user.
UID means user.
Idea and g.
ID g.
Eid Means Group ID.
Here some.
As you can see here, um, in your system, it might be different.
For example, in your system, it might be the 500 or different numbers.
So this is simply because.
In.
If you have if you are getting different numbers in Fedora, Fedora starts its numbering of regular
user accounts from 500.
So in fedora it starts from 500 while the Ubuntu and debian based system.
In this case kali linux is debian based.
It started from 1000.
So we can also see that the Kali Linux user belongs to a lot more groups and this has to do with the
way Ubuntu or Debian or Kali Linux manages privileges for system and devices.
So where does this information come from?
So like so many things in Linux it comes from a couple of text files.
So user accounts are defined in ETSI.
Passe.
W.
Actually, let me write that down here so you can use so.
E of sexual.
Right.
Clear e, t, C and p a s.
S w.
So all of these actions are defined in the Tcpa SSW file and the groups are defined in e t, c, obviously
group file group.
So when a user or user accounts and groups are created, these files are modified.
These files are modified along with the Etsy shadow.
So which and actually Etsy.
Shadow.
Etsy.
Shadow.
It is a shadow file.
Uh, he holds the information about the user password.
So for each user account, for example, ATC password files defines user login.
Name login login.
Name.
User ID, for example, in this case.
And as you can see, user ID, group ID account, real name, home directory, the login shell and,
and so on.
So if we examine the contents of Etsy passed w file that the user login name or actually it is passed
W and actually it is passed.
W d w here.
So.
Here.
If we examine this.
And the Etsy and Etsy Group.
We noticed that besides the regular user accounts, there are accounts for each super user.
In this case a super user accounts here, user ID is zero, super user accounts has zero super ID and
various other system users.
So in next lecture you will learn about the reading, writing and executing in Linux.
So I'm waiting you in next lecture.