Guest Post, Blog for computer hardware repairing services and networking

UGO Mode permission

In Linux for any directory or there are three types off permission you can provide,

1)      Read

2)      Write

3)      Execute

If a directory have read permission then you can read the content of the directory, if the directory  has write permission then you can edit the content of the directory, if the directory has execute permission then you can run that directory if it is a program directory.

If a directory has read permission then you can browse contains of the directory, if the directory has write permission then you can edit or delete contains of the directory, if the directory has execute permission then you can change to the directory or move inside to the directory.

Read permission is indicated by “r”, write permission is indicated by “w” and execute permission is indicated by “x”. All these three permission can be given to three types of entities – User, Group and Others. User is the creator or owner of any particular file or directory. Group is a collection of user who has the same rights and community as the owner. Others is the collection of those users who do not belong to the group of the owner. User is indicated by “u” Group is indicated by “g”, Others is indicated by “o”.

To provide permission use “+”and  to take away permission use “-“permission can be given or withdrawn by the” chmod” command.

(com) chmod (space) u/g/o (space) +/- r/w/x (space) file/directory

Octal Notation permission

You can also provide the permission by using “octal notation” where a three digit number is used to represent the entire permission set. Value for read permission is “4”, Value for write permission is “2” and Value for execute permission is “1”.

(com) chmod (space) u(421)g(421)o(421) (space) file/directory

The left most digit of the three digit (u,g,o), represents total permission for user, The middle digit of the three digit (u,g,o), represents total permission for group, The right most digit of the three digit (u,g,o), represents total permission for others. Each total (421) permission is the sum total of read, write, execute permission.

Sticky bit in Linux

It is a special attribute which can be applied to a directory of a user, if that directory is a publicly accessible directory that means other users have full permission to the directory of that user. When other users have full permission for the directory of a user then there is also possibility that this other users can very easily delete the file of the original user inside the directory. If sticky bit is given to that directory then this can’t be done. The other users will be only able to delete those files that are created by them and not by the original user.

How to enable sticky bit permission

(com) chmod (space) 1777 (space) directory name/ file

(com) chmod (space) go+t (space) directory name/ file

User ACL (Access control List) Linux

By using “chmod” you can give individual permission only to the owner or user the rest permission are all community permission like group and others. If you want to provide individual permission for a file or directory to a user who is not the owner, you have to use “ACL” follow below these steps.

1)      Activate ACL for the root file system

(com) vi (space) /etc/fstab [Then edit the file system default as (defaults,acl) then save and exit

(com) esc : x

2)       Then remount the root file system.

(com) mount (space) –o (space) remount (space) /

3)      Specify ACL for any other user

(com) setfacl (space) –m (space) u:(user name):(permission r/w/x) (space) file or directory name (home/user/file)

4)      How to check the “ACL”

(com) getfacl (space) file or directory name (home/user/file)

5)      How to remove the “ACL” permission

(com) setfacl (space) –x (space) u:(user name):(space) file or directory name (home/user/file)

How to see your present directory

(Com)   pwd

How to get the information regarding on particular command

(com)      man (space) commend name

                info (space) commend name {press q for exit]

How to auto complete any commend

(com) Type some latter and then press tab

How to see the path of that commend

(com) which (space) commend name

How to create a directory

(com) mkdir (space) directory name

How to create parent directory and sub directory

(com) mkdir (space) –p (space) a/b/c/d

How to change directory

(com) cd (space ) directory name

How to go parent directory

(com) cd (space) ..

How to go home directory by one shot

(com) cd

How to remove directory

(com) rmdir (space) directory name [This commend can only remove empty directory]

(com) rm (space) –r (space) directory name [ Remove directory with content]

How to see the content of a directory

(com) ls (space) –l (space) directory name

How to see content  of directory as pagewise

(com) ls (space) –l (space) directory name (space) | (space) more

How to create a file

(com) cat (space) > (space) file name[After putting data press Ctrl D to save and exit]

How to create more than one empty file in one shot

(com) touch (space) file name (space) file name (space) ……….

How to display content of a file

(com) cat (space) file name

How to display content of file with line number

(com) cat (space) –b (space) file name

How to add content to another file

(com) cat (space) source file (space) >> (space) destination file

How to rename file

(com) mr (space) old name (space) new name

How to transfer a file one location to another location

(com) mv (space) file name (space) destination directory

How to create duplicate of a file

(com) cp (space) source file (space) destination file

How to create duplicate of a file in another location

(com) cp (space) source file (space) destination directory

How to create hard link of a file

(com) ln(space) original file (space) hard link file

How to create soft link of a file

(com) ln(space) –s (space) original file (space) soft link file

How to delete a file

(com) rm (space) file name

How to find out whether a pattern exists in a file

(com) grep (space) search pattern (space) file name

How to ignore the case of search pattern

(com) grep (space) –i

How to find out the line with the line numbers having that search pattern

(com) grep (space) –n

How to find out the number of occurrences of the search pattern

(com) grep (space) –c

How to display the line which not having the search pattern

(com) grep (space) –v

How to show combine content of two files in a side by side fashion

(com) past (space) first file name (space) second file name

How to show combine content of two files one below the other

(com) past (space)-s (space) first file name (space) second file name

How to compare between two files

(com) cmp (space) first file name (space) second file name

How to display unique common part between two files

(com) comm (space) first file name (space) second file name

How to short a file

(com) short (space) file name

How to reverse short a file

(com) short (space)-r

How to find a numeric short in a file

(com) short (space)-n

How to short a database file

(com) short (space)-t “Field separator :/I” (space) –k-shorting field number (space) file name

How to display the first two lines of a line

(com) head (space) file name

How to display some specific line from the top

(com) head (space) –n (no of line) (space) file name

How to display last 10 lines

(com) tale (space) file name

How to display some specific line from the end

(com) tail (space) –n (no of line) (space) file name

How to display some specific no of line from in between head and tail both

(com) head (space) –n (no of line 15) (space) file name shift+| (space) tail (space) –(no of line 5)

Linux is an open sources operating system. It was invented by Linus Torvalds. He actually created the Linux kernel and put it on the net so anybody can download it, create and customize sell on it and produce new distribution of Linux known as Linux distribution for example –

1. Red hat

2. Ubuntu

3. Debain

4. Mandriva

5. Bodhi linux

6. Suse linux

Among all of this Red Hat as a lion shear and it has a well organize training methodology and curriculum. So, to know Linux communities you must go for Red hat Linux. The commence of Red hat Linux a sum which is similar to the other version of Linux. Red hat produce two types of Linux –

• “fedora”

• “enterprise”

Fedora is a free version where as enterprise Linux is paid version and this payment is required when you are going for several other services form the Linux community. Red hat Linux kernel at present is 2.6 kernel. In fact Red hat Linux kernel is characters by major number, minor number and revision number. Revision number indicates small up gradation and revision for the Linux kernel , Minor number indicates sum more significance development and if the minor number is even then it indicates a fully tried and tested stable kernel which is suitable for the corporate , if the minor number is odd then that kernel is not fully tested . So it is suitable for school, college etc. The major number indicates a radical change of the kernel.

Important system directories:

[/] root directory- this directory is use to hold the enter Linux system.

[/boot] this directory is hold the important booting files of Linux.

[/root] this is the home directory for the root user and contended all the important directory and documents of the root user.

[/home] this directory holds the home directory of all the others users of the Linux.

[/bin] this directory holds the different executable file which is related to the different user processes.

[/sbin] this directory holds the executable file which is required by the system.

[/dev] this directory holds the different device file.

[/mnt] this directory holds the mount point directory for the different partition of hard disk

[/media] this directory holds the mount point directory of the removable media

[/etc] this directory holds the different configuration for the difference service offered by Linux.

[/user] this directory holds the difference library file that the necessary for the system.