Changes between Version 7 and Version 8 of ubuntuinstall

Timestamp:

Nov 17, 2016, 10:12:48 AM (8 years ago)

Author:

admin

Comment:

--

ubuntuinstall

@@ -387 +387 @@
 }}}
 Add the lines with enter key at the end. After inserting all the lines press Ctrl + D
-{{{
+ {{{
 one
 two
 . .
 ten
-}}}
+ }}}
  - View the file you created using less and cat
 '''cat'''
@@ -481 +481 @@
 }}}
 
+=== File Permission ===
+ 
+ - Commands preceded with "$" imply that you should execute the command as a general user - not as root.
+ - Commands preceded with "#" imply that you should be working as root with "sudo"
+ - Commands with more specific command lines (e.g. "RTR-GW>" or "mysql>") imply that you are executing commands on remote equipment, or within another program.
+
+'''chmod''': Change file read write permission
+'''chown''': Change the owner of the file
+'''chgrp''': Change the group of the file
+
+==== Reference ====
+
+If you look at files in a directory using "ls -al" you will see the permissions for each file and directories. Here is an example:
+{{{
+drwxrwxr-x    3 root   root       4096 Feb 25 09:49 directory
+-rwxr--r--   12 root   root       4096 Feb 16 05:02 file
+}}}
+
+So, the directory has r (read), w (write), x (execute) access for the User and Group. For Other it has r (read) and x (execute) access. The file has read/write/execute access for User and read only access for everyone else (Group and Other).
+
+To change permissions you use the '''chmod''' command. chmod uses a base eight (octal) system to configure permissions. Or, you can use an alternate form to specify permissions by column (User/Group/Other) at a time.
+
+Permissions have values like this:
+{{{
+Letter  Permission   Value
+
+R       read         4
+W       write        2
+X       execute      1
+-       none         0
+}}}
+
+Thus you can give permissions to a file using the sum of the values for each permission you wish to give for each column. Here is an example:
+{{{
+Letter  Permission                   Value
+
+---     none                         0
+--x     execute                      1
+-w-     write only (rarely used)     2
+-wx     write and execute (rare)     3
+r--     read only                    4
+r-x     read and execute             5
+rw-     read and write               6
+rwx     read, write, and execute     7
+}}}
+This is just one column. Since we have three areas of permissions (User, Group, Other), it looks like this will all 3 sets:
+{{{
+Permissions  Numeric      Description
+             equivalent  
+
+-rw-------   600          User has read & write permission.
+-rw-r--r--   644          User has read & write.
+                          Group and Other have read permission.
+-rw-rw-rw-   666          Everyone (User, Group, Other) have read & write
+                          permission (dangerous?)
+-rwx------   700          User has read, write, & execute permission.
+-rwxr-xr-x   755          User has read, write, & execute permission.
+                          Rest of the world (Other) has read & execute
+                          permission (typical for web pages or 644).
+-rwxrwxrwx   777          Everyone has full access (read, write, execute).
+-rwx--x--x   711          User has read, write, execute permission.
+                          Group and world have execute permission.
+drwx------   700          User only has access to this directory.
+                          Directories require execute permission to access.
+drwxr-xr-x   755          User has full access to directory. Everyone else
+                          can see the directory.
+drwx--x--x   711          Everyone can list files in the directory, but Group
+                          and Other need to know a filename to do this. 
+}}}
+==== Exercise ====
+
+ - Go to the numbers directory and get a detailed list
+{{{
+$ cd numbers
+$ ls -al
+total 24
+drwxr-xr-x  3 dilum dilum 4096 Nov 17 13:53 .
+drwxrwxrwx 50 dilum dilum 4096 Nov 17 13:10 ..
+-rw-r--r--  1 dilum dilum   42 Nov 17 13:08 numbers2.txt
+-rw-r--r--  1 dilum dilum   91 Nov 17 13:08 numbers3.txt
+-rw-r--r--  1 dilum dilum   49 Nov 17 13:08 numbers.txt
+drwxr-xr-x  3 dilum dilum 4096 Nov 17 13:08 one
+
+}}}
+ - Change file permission as follows
+{{{
+$ chmod 044 numbers.txt 
+}}}
+Now you have remove read privilege try view the file using cat
+{{{
+$ chmod 444 numbers.txt
+}}}
+Now you have set privilege as read only. Open the file via vi editor and try to edit the file
+
+ - Switch to root user 
+{{{
+$ sudo su
+}}}
+
+ - Change the ownership and group of the numbers2.txt to root and make it read only for all the other users.
+ - Change the ownership and group of the numbers3.txt to root and remove all the privileges from all the other users.
+ - Switch back to your user and try to view numbers3.txt and try to edit numbers2.txt
+{{{
+# chown root numbers2.txt 
+# chgrp root numbers2.txt 
+# chown root numbers3.txt
+# chgrp root numbers2.txt  
+# chmod 700 numbers3.txt 
+# chmod 744 numbers2.txt 
+# su 'Your username'
+$ cat numbers3.txt 
+cat: numbers3.txt: Permission denied
+$ cat > numbers2.txt 
+bash: numbers2.txt: Permission denied
+}}}
+
+=== More Linux Commands === 
+
+'''who am i''':
+'''df -dh''':
+'''man''':
+'''date''':
+'''time''':
+'''ln''':
+'''ps''':
+'''kill''':
 
 === Setting UP IP Addresses ===
@@ -487 +613 @@
 Get your IP address from the [wiki:ipallocation IP table]
 {{{
+
 
 iface eth0 inet static