Skip to main content

LINUX Managing file/folder permissions and ownership

The Unix files access is controlled. There are three types of access (permissions):

  • read
  • write
  • execute
Each file belongs to a specific user and group (ownership).
Access to the files is controlled by user, group, and what is called other/everyone permission bits and is usually set using a numerical value.
For example, 644 as permission bit will result in:
Owner / User Group Other/ Everyone 644
Each number represents the access level and it can be from 0 to 7.

The access level, depending on the number is as follows:

  • 0 - no access to the file whatsoever
  • 1 - execute permissions only
  • 2 - write permissions only
  • 3 - write and execute permissions
  • 4 - read permissions only
  • 5 - read and execute permissions
  • 6 - read and write permissions
  • 7 - read, write and execute permissions (full permissions)

Thus the above 644 permissions example will look like this:

Owner / User - Read and Write Group - Read and Write Other/ Everyone - Read only
To allow a script to be executed and read by everyone but the only one who can write in it is your user, you would need to set 755 as permissions:
  • Owner / UserGroupOther/ Everyone
  • 7 - Full permissions
  • 5 - read and execute
  • 5 - read and execute
Changing the permissions to 700 will make the file visible only for your username and no one else and setting it to 444 will allow only the file creator to modify it.
The command you need to issue to actually change the permissions is called ‘chmod’ and it generally looks like this:
chmod 755 configuration.php
The above example changes the permissions of configuration.php file and sets them to 755.
You can recursively change the permissions of all folders and files using the recursive argument:
chmod -R 755 *This will modify the permissions of all files in the current folder and
set them to 755.
You might wonder what the above user/group values are. These two settings are the actual ownership flags for a file or a folder.
Each file has a primary user that owns it and a group assigned to it. To change those values, a special command exists -- ‘chown’.
Its syntax is very easy:
chown user: group file
For example:
Chown user:
siteground configuration.php
The above line will set the owner of the file to ‘user’ and the group to ‘siteground’.
Changing ownership recursively is also permitted and the flag (naturally) is -R: chown -R user: siteground *

Comments

Post a Comment

Popular posts from this blog

C++ How to use Date and Time

The C++ standard library does not provide a proper date type. C++ inherits the structs and functions for date and time manipulation from C. To access date and time related functions and structures, you would need to include <ctime> header file in your C++ program. There are four time-related types: clock_t, time_t, size_t , and tm . The types clock_t, size_t and time_t are capable of representing the system time and date as some sort of integer. The structure type tm holds the date and time in the form of a C structure having the following elements: struct tm { int tm_sec ; // seconds of minutes from 0 to 61 int tm_min ; // minutes of hour from 0 to 59 int tm_hour ; // hours of day from 0 to 24 int tm_mday ; // day of month from 1 to 31 int tm_mon ; // month of year from 0 to 11 int tm_year ; // year since 1900 int tm_wday ; // days since sunday int tm_yday ; // days since January 1st int tm_isdst ; // hours of daylight savin...
Post a Comment
Read more

PERL Some good framework

1. Catalyst is the most popular agile Perl MVC web framework that encourages rapid development and clean design without getting in your way. Catalyst | Perl MVC web application framework 2. Mojolicious is a next generation web framework for the Perl programming language. Back in the early days of the web, many people learned Perl because of a wonderful Perl   ... Mojolicious - Perl real-time web framework 3. Documents for Perl  The Perl Archive Network, the gateway to all things Perl. The canonical location for Perl code and modules. The Comprehensive Perl Archive Network - www. cpan .org
Post a Comment
Read more

PHP Error and Exception Handling

Error handling is the process of catching errors raised by your program and then taking appropriate action. If you would handle errors properly then it may lead to many unforeseen consequences. Its very simple in PHP to handle an errors. Using die() function: While wirting your PHP program you should check all possible error condition before going ahead and take appropriate action when required. Try following example without having /tmp/test.xt file and with this file. <?php if(!file_exists("/tmp/test.txt")) { die("File not found"); } else { $file=fopen("/tmp/test.txt","r"); print "Opend file sucessfully"; } // Test of the code here. ?> This way you can write an efficient code. Using abive technique you can stop your program whenever it errors out and display more meaningful and user friendly meassage. Defining Custom Error Handling Function: You can write your own function to handling any error. PHP provides y...
Post a Comment
Read more