Latest in the Section
- HTC Android 4.2.2 One will arrive in two weeks
- Spain, how to market experimental mobility?
- Chops (and XXXVIII) - Change the resolution of a video with ffmpeg
- Individuality of identical twins
- goal: augmented reality interface world's most advanced
- Apple retira Bang with Friends para iPhone de la App Store
- Telcel What is the plan that suits you?
- Apple strikes back and removes Bang With Friends from the App Store
- Apple retira Bang With Friends de la App Store
- IFTTT Recipes to take advantage of LinkedIn
Popular in the Section
- Uncharted 2 was one of the best games of 2009
- Synergy-Plus program, which allows us to control with a single keyboard and mouse several machines
- VBulletin case: "This decision is a true cross-Shirt to Spanish sovereignty"
- Inadvisable online mode of FIFA 2010 with Gamblers Anonymous
- Blood Moon, the adventures of the undead
- Olloclip brings the iPhone's camera to the next level
- Sasha Grey, Hulk Hogan y Daniel Dae Kim protagonizarán Saints Row: The Third
- Heavy Rain, Quantic Dream ultimate
- Party at home with friends and a dealer hand of Four Roses
- Dragon Age: Origins and the mod called "Natural Bodies"
|Technology - Software|
|Thursday, 09 August 2012 02:28|
Yesterday we spent a few minutes to discuss one aspect that often leads to confusion, and occasional headache, among users who are getting started in the administration of systems based on Unix , Linux or Mac OS X : The file and folder permissions . After knowing what are the permissions, what types of permits are there and what they are, now let's continue with this topic from a more practical view since we focus on the notation usually used to express the permissions folders and files: symbolic notation octal notation.
To summarize what we discussed yesterday, a user might have permissions to read, write or execute on a given file (in the case of a folder only come from the first two and, in the case of reading, it implies that we can navigate within folder). In addition, permits were from the user perspective and distinguished permissions to the file owner, the group ownership and permissions for other users of the system (UGO, User, Group, Others). In other words, a file will present 3 sets of permissions, ie a set of permissions (read, write and execute) to the owner, group and other system users.
Logically, this information must be visible by the administrator and, above all, easily understandable. With this idea, is quite common to use a symbolic notation with which to represent, through a combination of 10 characters, the permissions that a file or a directory.
Within these 10 characters, the first represents the type of "object" that we are driving, ie a file, directory, link, etc.. The most common characters are:
After this first character adds a further nine triplet representing the permissions for each of the three user perspectives that exist, ie 3 characters to represent the permissions of the file owner, 3 characters to represent the group permissions and other 3 to represent the permissions of other users of the system. The shortlist follows the order read-write-execute and is represented by the characters 'r', 'w' and 'x' character to appear when the permits and appearing have a dash ('-') when not possess such permits .
That is, if when listing the contents of a folder from the console we get something like
Once understood the rules governing the use of symbolic notation comes time to enter the part that we may be, at first sight, somewhat more complicated: the octal notation.
What is the octal notation? Is a representation of the permissions of the files using digits instead and use strings of characters. Specifically, each of the last 8 characters of symbolic notation (which defines permissions) is replaced by one bit to 1 if the permission has been granted and a 0 otherwise, ie
This numerical notation is quite common in use and, for example, is something that we see in the file management offered by many hosting providers or, if we manage a console, when we change the permissions of a file in Linux using the command chmod.
If you have not mastered very well converting to octal, we can store the following rule:
Knowing how this notation, from now on should be easier to understand what resultarnos mean permission as usual as the 775, 644, the 777 or 600:
Now what do we do?
To close the circle next installment to devote a few tips aimed at improving the security of our web server using the appropriate permissions to files and also discuss some additional details.
Images: The Void Ghost and