CHMOD: Changing File Permissions Online

In the beginning, man created the Internet. Man saw that the Internet was very, very good.

From its inception, the Internet was about communication: one computer communicating with another, people from all over the world communicating with one another. While early in its development most Internet pages were HTML (Hypertext Markup Language) based and therefore static, the trajectory has always been the next level of customization and interactivity. The highly interactive aspects of the Internet have spread as more people tackle creating their own forums and their own blogs, foregoing sites where layout may be rigid and banner ads are de riguer. Thanks to an explosion of software - some paid, some free or donation-only, almost anyone can build an interactive page on their own domain.

There are several steps in the process, but there's a simple little detail that's critical to interactivity: it's changing file permissions, or CHMOD. Generally speaking, the installation of a PHP or ASP script requires simple CHMOD actions.

CHMOD 101, The Basics

The principle behind file permissions is simple. If a file will be edited online - for instance, a new blog entry page - the server needs to allow a user to modify it. The default is read-only when a file is uploaded. In order to change that, the webmaster has to access the uploaded file and tell the server that modifications are allowed. That process is known as CHMOD, shorthand for Change Mode.

Whether using an FTP client like FileZilla or SmartFTP, or using Internet Explorer's native folder view to upload files, the general process to change file permissions is the same.

CHMOD only applies to files that are already uploaded. Open the directory (or folder) that contains the file to be modified. Right-click on the file, which will create a dropdown menu. Select Properties, the last option in the dropdown. That action will open a window with file information, including a group of nine check boxes in three rows of three columns. The left column is for read permission; the middle column is for write permission; and the third column is for execute permission. Rows identify which user or users can modify files - the first is owner, the second is group, the third is all users (in some cases marked "other.")

Checking group and/or all users doesn't necessarily mean it's open season on the file in question. There are typically other constraints (such as password access) governing the process, built into associated files and databases.

Once the appropriate boxes are checked, click on the OK button to save changes.

CHMOD File Permissions Values

Install instructions frequently assign a numeric value to the CHMOD portion of an install. A CHMOD 777 means that all nine boxes are checked, allowing the online file to be read, written/rewritten and executed. A CHMOD 766 eliminates the execution mode for all but the owner; CHMOD 755 is read and execute but doesn't permit an online edit. CHMOD 744 is read-only for anyone but the webmaster.

Side note: don't uncheck the boxes in the owner row - or at least don't uncheck read and write. Doing so may prevent deletion or overwriting of a corrupt file down the line.

Most pre-made scripts specify which files should be changed to which level of permissions. Occasionally the install directions will call for a CHMOD value of 666. That simply means read and write capabilities across the board but no execution boxes checked. Setting the CHMOD to 766, allowing the owner (webmaster) to execute, will not prevent the script from working. In fact, it may be necessary down the line if a subsequent upgrade is needed.

CHMOD Errors

If you've ever visited a website and received a message about needing authorization, or saying you don't have the appropriate permissions to access a given page, it could well be that the webmaster forgot to change the permissions on a key file. If you're that webmaster, it's time to get out the original installation instructions and compare permissions on your site with those listed in the directions.

On rare occasions, there is a permissions issue with the server itself. When that's the case, the files may revert to read mode after changing, or may look fine but deletion isn't possible. (If having problems with deleting a directory, always check permissions on the files it contains. Chances are one or more are set to read/write only.) When file permission issues arise with a server, the hosting service must make any necessary changes to allow a script to execute properly.

Temporary Changes

Some scripts require only temporary changes to file permissions. If so, CHMOD per directions, execute the script, then CHMOD back to read-only mode (generally 744.) The process is the same - just uncheck the appropriate boxes and click the OK button to save.