Merge pull request kodekloudhub#2 from rahulsoni43/master

Linux Course Documentation by RahulSoni

docs/06-Security and File Permissions/01-The Security Incident(story).md

@@ -0,0 +1,3 @@
+# Security Incident (story)
+
+  Take me to the[Story](https://kodekloud.com/courses/873064/lectures/17074490)

docs/06-Security and File Permissions/02-Linux Accounts.md

@@ -0,0 +1,100 @@
+# LINUX ACCOUNTS
+
+  - Take me to the [Tutorial](https://kodekloud.com/courses/873064/lectures/17074499)
+  - In this section we will take a look at basic access control in Linux.
+  - We will also learn about about the file permissions. Lets Get Started!
+
+    ![linux](../images/linux.PNG)
+
+
+  #### User Accounts
+
+  - User's informations are stored under **`/etc/passwd`** file.
+
+    ```
+    [~]$ cat /etc/passwd
+    ```
+
+  - Information about groups is stored into  **`/etc/group`** file.
+
+    ```
+    [~]$ cat /etc/group
+    ```
+   
+    ![user](../images/user.PNG)
+    
+  - Each user has a username and a unique ID assigned to them known as user ID or UID.
+  - The user also has a GID, the group id they are part of, **`id`** command can be use to check these details. for eg:
+
+    ```
+    [~]$ id michael
+    uid=1001(michael) gid=1001(michael)groups=1001(michael),1003(developers)
+    ```
+  
+  - More details about the user account can be found eg. default shell, home directory using.
+
+    ```
+    [~]$ grep -i michael /etc/passwd
+    michael:x:1001:1001::/home/michael:/bin/sh
+    ```
+   
+    ![group](../images/group.PNG)
+
+  - To see the list of users currently logged use **`who`** command.
+
+    ```
+    [~]$ who
+    bob pts/2 Apr 28 06:48 (172.16.238.187)
+    ```
+
+  - The **`last`** command displays the record of all logged-in users along with the date and time when the system was rebooted.
+
+    ```
+    [~]$ last
+    michael :1 :1 Tue May 12 20:00 still logged in
+    sarah :1 :1 Tue May 12 12:00 still running
+    reboot system boot 5.3.0-758-gen Mon May 11 13:00 - 19:00 (06:00)
+    ```
+
+  #### Switching users
+
+  - To switch to any user use **`su`** command.
+
+    ```
+    [~]$ su –
+    Password:
+
+    root ~#
+    ```
+ 
+  - To run a specific command you can use **`su -c "whoami"`** (This is not recommended way)
+
+    ```
+    [michael@ubuntu-server ~]$ su -c "whoami"
+    Password:
+    root
+    ```
+
+  - To run a command as a root user **`sudo`** command is recommended.
+
+    ```
+    [michael@ubuntu-server ~]$ sudo apt-get install nginx
+    [sudo] password for michael:
+    ``` 
+    
+    ![who](../images/who.PNG)
+
+  - Users listed in /etc/sudoers file can make use of sudo command for privledge escalation.
+
+    ```
+    [~]$ cat /etc/sudoers
+    ```
+    ![sudo](../images/sudo.PNG)
+
+  - To restrict anyone from directly login as root login, this can be done by setting **`nologin`** shell.
+
+    ```
+    [~]$ grep -i ^root /etc/passwd
+    /root:x:0:0:root:/root:/usr/sbin/nologin
+    ```
+    

docs/06-Security and File Permissions/03-User Management.md

@@ -0,0 +1,74 @@
+# USER MANAGEMENT
+
+  - Take me to the [Tutorial](https://kodekloud.com/courses/873064/lectures/17074501)
+  - In this lecture we will learn how to create and manage user accounts in Linux.
+
+  #### User Add
+
+  - To create a new local user **`bob`** in the system use **`useradd`** command.
+
+    ```
+    [~]$ useradd bob
+    ```
+
+  - To get more details about **`bob`** account like, home director, uid, and shell use **`/etc/passwd`**
+
+    ```
+    [~]$ grep -i bob /etc/passwd
+    bob:x:1002:1002::/home/bob:/bin/sh
+    ```
+
+    ![useradd](../images/useradd.PNG)
+  
+  - To check the uid or username of the user logged in user **`whoami`** command.
+
+    ```
+    [~]$ whoami
+    bob
+    ```
+
+  - All user's password are store under **`/etc/shadow`**
+
+    ```
+    [~]$ grep -i bob /etc/shadow
+    bob:!:18341:0:99999:7:::
+    ```
+ 
+  - To change the password of current user use **`passwd`** or for any specific user use **`passwd <username>`** 
+
+    ```
+    [~]$ passwd bob
+    Changing password for user bob.
+    New UNIX password:
+    Retype new UNIX password:
+    passwd: all authentication tokens updated
+    successfully.
+    ```
+
+  # Managing Users
+
+  - **`useradd`** command be used along with many attributes as show below.
+
+    ```
+    [~]$ useradd -u 1009 -g 1009 -d /home/robert -s /bin/bash -c ”Mercury Project member" bob
+    ```
+
+    ![manage](../images/manage.PNG)
+     
+  - To delete a user use **`userdel`** command
+
+    ```
+    [~]$ userdel bob
+    ```
+
+  - To add a group use **`groupadd`** command 
+
+    ```
+    [~]$ groupadd –g 1011 developer
+    ```
+
+  - To delete a group user **`groupdel`** command
+
+    ```
+    [~]$ groupdel developer
+    ``` 

docs/06-Security and File Permissions/04-Access Control Files.md

@@ -0,0 +1,44 @@
+# ACCESS CONTROL FILES
+
+  - Take me to the [Tutorial](https://kodekloud.com/courses/873064/lectures/17074502)
+
+  - Access Ccontrol files are stored under **`/etc`**.
+  - Can be read by anyone and can be only edited by **`root`** user.
+
+
+  ### Control files
+
+  - To get more details about one's account for example **`bob`** account, home director, uid, and shell check **`/etc/passwd`** 
+
+    ```
+    [~]$ grep -i ^bob /etc/passwd
+    bob:x:1002:1002::/home/bob:/bin/sh
+    USERNAME:PASSWORD:UID:GID:GECOS:HOMEDIR:SHELL
+    ```
+   
+    ![passwd](../images/passwd.PNG)
+
+  - Password are stored under **`/etc/shadow`**
+
+    ```
+    [~]$ grep -i ^bob /etc/shadow
+    bob:$6$0h0utOtO$5JcuRxR7y72LLQk4Kdog7u09LsNFS0yZPkIC8pV9tgD0wXCHutY
+    cWF/7.eJ3TfGfG0lj4JF63PyuPwKC18tJS.:18188:0:99999:7:::
+
+    USERNAME:PASSWORD:LASTCHANGE:MINAGE:MAXAGE:WARN:INACTIVE:EXPDATE
+    ```
+
+    ![shadow](../images/shadow.PNG)
+
+  - Check the groups **`bob`** belongs too
+
+    ```
+    [~]$ grep -i ^bob /etc/group
+    NAME:PASSWORD:GID:MEMBERS
+    ```
+
+    ![egp](../images/egp.PNG)
+
+# HANDS-ON LABS
+
+  - Lets start with Managing and User Accounts [here](https://kodekloud.com/courses/the-linux-basics-course/lectures/17074503)

docs/06-Security and File Permissions/05-File Permissions.md

@@ -0,0 +1,114 @@
+# LINUX FILE PERMISSIONS
+
+  - Take me to the [Tutorial](https://kodekloud.com/courses/873064/lectures/17074504)
+
+  - In this lecture we will learn about various file type identifiers.
+  - We will also learn about various Linux file permissions that can be applied on the file or the directory.
+
+    ![perm](../images/perm.PNG)
+
+
+    ![type](../images/type.PNG)
+
+
+  #### Directory Permission
+
+  - To list the directory permission use
+
+    ```
+    [~]$ ls -ld /home/bob/random_dir
+    ```
+
+  - To know the current user 
+
+    ```
+    [~]$ whoami
+    ```
+ 
+  - To change the change the directory
+
+    ```
+    [~]$ cd /home/bob/random_dir
+    ```
+
+  #### File Permissions
+
+  - Linux file permissions are defined as 
+
+    ![filep](../images/filep.PNG)
+
+  #### Modifying file permissions
+
+  - Use **`chmod`** command to modify the file permissions.
+
+  - Provide full access to owners
+
+    ```
+    [~]$ chmod u+rwx test-file
+    ```
+
+  - Provide Read access to Owners, groups and others, Remove execute access
+
+    ```
+    [~]$ chmod ugo+r-x test-file
+    ```
+
+  - Remove all access for others
+
+     ```
+     [~]$ chmod o-rwx test-file
+     ```
+
+  - Full access for Owner, add read , remove execute for group and no access for others
+
+    ```
+    [~]$ chmod u+rwx,g+r-x,o-rwx test-file
+    ```
+ 
+  - Provide full access to Owners, group and others
+
+    ```
+    [~]$ chmod 777 test-file
+    ```
+
+  - Provide Read and execute access to Owners,groups and others
+
+    ```
+    [~]$ chmod 777 test-file
+    ```
+
+  - Read and Write access for Owner and Group, No access for others.
+
+    ```
+    [~]$ chmod 660 test-file
+    ```
+
+  - Full access for Owner, read and execute for group and no access for others.
+
+    ```
+    [~]$ chmod 750 test-file
+    ```
+
+  #### Change Ownership 
+   
+  - Changes owner to bob and group to developer
+   
+    ```
+    [~]$ chown bob:developer test-file
+    ```
+    
+  - Changes just the owner of the file to bob. Group unchanged.
+
+    ```
+    [~]$ chown bob andoid.apk
+    ```
+
+  - Change the group for the test-file to the group called android. 
+
+    ```
+    [~]$ chgrp android test-file
+    ```
+
+# HANDS-ON LABS
+
+  - Lets do some hands on labs to understand File Permission better. [Take me to Labs](https://kodekloud.com/courses/873064/lectures/17074516)