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Let me start, guys, by explaining you Structure of Linux file system.

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Linux files and directories are located in a tree like structure at the root.

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There is a root directory that is represented simply by forward slash.

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Then this root directory has some subdirectories like bin as bin and so on.

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Those subdirectories may have own subdirectories and also files.

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It means that every directory could be considered as a branch of this tree and every file is a leaf.

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And again, all those branches and leaves start from root directory represented simply by forward slash.

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When any user logs into Linux system, he or she actually logs into own home directory.

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And the home directory of every user is represented by tilde sign.

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That's why we see the sign here after logging into Linux system.

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All right.

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Next, you could find the current directory you are currently in by entering the following command.

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P.

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W.

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D.

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That stands for print working directory.

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Let's press enter.

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And now I see that I am located in slash root folder.

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Please notice that absolute paths in Linux start from forward slash and here we see actually absolute

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path to a specific folder to a specific directory.

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If I go to other ubuntu virtual machine and type p w here, I will see that home folder for this.

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Bogdan user is different here and it is slash home slash Bogdan.

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And this path differs from this path and difference here appears because here we are logged in as root

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user into Linux docker container and in this case I'm logged in as regular user and home folders for

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all regular users are located in the home folder located in the root directory.

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All right, next command.

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You are able to CD to root of the file system in Linux computer using following command CD and forward

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slash forward slash represents root directory in any Linux operating system.

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Let's see DB2 root directory and notice that the command prompt here was changed and now see forward

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slash instead of tilde sign.

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And if I type p.w.d. here now I'll see that now I'm located in root directory.

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You could always go back to your home directory for your logged in user by entering simply CD like this.

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And now I'm back into home directory and if I type PWD, I see path to my home directory.

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For this root user it is simply slash root.

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All right.

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That's how you could change directory and move either to home folder or to root folder.

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Next, let me demonstrate you how you could move into specific folder.

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For example, if I list the files and folders here in home folder for this root user, I will see actually

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empty list.

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And that means that there are no files and folders inside of the home directory for this user.

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And if I go to root folder like so and list files and folders here, I'll see such folders as home media

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and so on.

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If you want to go into specific folder, for example, let's go into run folder.

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You could type, CD and type I is a relative path or absolute path.

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If you are already located in specific folder, you could use relative path.

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And in this case I could simply type run like so.

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And now I'm inside of the run folder and if I enter P.w.d. now I will see that now I'm inside of the

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slash run folder and this path that starts with forward slash is absolute path and you are always able

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to go into specific folder using absolute path to this folder.

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Let me show you that.

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For example, let's list folders here and let's CD into mount folder like So here again I'm using relative

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path and now here if I'll enter CD forward slash boot, I'll go into the boot folder located in the

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root directory enter and now I'm inside of the boot folder.

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That's because I have just used absolute path.

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All right.

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That's how you could move into specific folder using relative path or absolute path.

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Also, let me show you now what is the meaning of dot and two dots here.

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When you use CD command, If I type simply CD and dot, nothing will change because Dot represents current

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working directory.

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This directory CD in this case slash boot.

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But if I type CD and two dots, I will go one level up to the parent directory and in this case I will

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go to root directory CD two dots, and now I'm inside of the root directory represented by Slash.

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All right.

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Let me now show you how to use Tab in order to autocomplete names of the directories and files.

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If I type here, CD slash and press tab twice, I'll see all possible directories and files that are

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located in the root folder.

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And if I type for example M and press tab twice, I'll see all possible directories and files that start

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with M.

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If I add additional letter here and press tab only single time, I'll see that this folder name will

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be autocompleted to media.

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That's because now there is just a single option that starts with M.

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All right.

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If I press tab twice now at this moment of time I see actually empty list.

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And that means that the media directory does not have any subdirectories.

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Let me remove media from here and let's go into folder like so and if I press tab now twice I see all

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possible options of file names and directories that I could use after e.t.c..

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And for example, here I see as l folder.

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And if I type here esky and press tab, I'll see that the directory name will be autocompleted to L

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if I press tab.

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Now here I see that there are only files called dot bash log out, dot bash RC and dot profile and there

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are no subdirectories inside of the SRC directory.

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All right, let's suppose that I want to go into this directory for this.

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I'll remove this last dot that was autocompleted and press enter here and now I'm inside of the src

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directory.

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Let me clear terminal and if I enter PWD, I will see this absolute path that starts always with forward

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slash.

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All right.

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If I want to go out from this SRC folder, I could simply type CD and two dots.

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It will go one level up to directory.

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Let me go back to CD here.

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I could use relative path because I'm already located in directory and press enter here and let's suppose

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that I want now to go to another sub directory of directory.

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For that I could simply type CD two dot, then forward slash and if I press tab twice here at this moment

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I will see all possible directories and files inside of the folder.

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And for example, let's go to dpkg directory.

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Let's start typing d p press tab.

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Yes it was autocompleted.

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Let's press tab twice here and I see that this dpkg directory contains origins sub directory.

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Let's go into it.

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I could type simply o and press tab.

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It will be autocompleted and let's press tab twice here and I see several files.

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Notice that at the end of every directory there will be forward slash.

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And that's how I recognize that this is directory and this is also directory.

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But this is file.

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And now I see that this origins directory contains only three files Debian default and ubuntu.

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All right, let's press enter.

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And now I'm inside of the origins directory.

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That's how you could use two dots in order to go into parent folder and go into some sub folders of

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that parent folder.

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Great.

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Let me type simply CD and I have returned back to my home directory and type CD.

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I'll see that now I'm again inside of the slash root folder.

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And again this directory is a home directory for root user and please notice that there is difference

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between slash root directory and simply slash directory.

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Slash directory is a root directory for all files and folders in Linux.

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It is a root of file system in Linux, but slash root is sub folder that is located in the root of file

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system in Linux and it represents home directory for root user.

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Please keep in mind that.

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All right, that's all what I wanted to explain you here in this lecture and now you understand what

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is the difference between root directory, absolute path and relative path and how to locate the current

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directory you are currently in.

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That's all for this lecture.

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And next, let me explain you how to manage files, how to create new files and how to list files.

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I'll see you in the next lecture.

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Bye bye.