If you're new to scripting, or getting the dreaded "Internal Server Error" when you try to run a sample script you've downloaded, its probably incorrect file permissions.

Linux allows you to set different levels of access to a file for different groups of people. This allows you to let the web server modify a file via a CGI script, for instance, while preventing other users from having normal access to the file. There are three groups in terms of file access, and three different permission types they can receive.

The groups are:

* User/Owner - the "user" group consists only of the owner of the file (your account, in most cases)

* Group - the "group" group consists of the other users on the server -- you can usually remove their permissions entirely if you think it necessary

* Other/World - the "other" group consists of everyone else -- most importantly, the web server falls into the "other" category

The potential permissions are:

* Read - the read permission allows a user or program the ability to read the data in a file

* Write - the write permission allows a user or program the ability to write new data into a file and to remove data from it

* Execute - the execute permission allows a user or program the ability to execute a file if it is a program or script.

Some things to keep in mind about your files:

* pages should be readable/writable by the owner and readable by the web visitor.
* scripts should be readable/writable/executable by the owner and readable/executable by the web visitor.
* data-config files should be readable/writable by the owner and readable/writable by the web visitor.

Use the following guide:

* --- (or 0) = no permission
* r-- (or 4) = read-only permission
* rw- (or 6) = read/write permission
* r-x (or 5) = read/execute permission
* rwx (or 7) = read/write/execute permission

Sometimes you'll see these numbers referenced for a script. For instance, "chmod your script to "755" or "777". That means "set file permissions to "Read-Write-Execute/Read-Execute/Read-Execute". "755" is in fact the most common setting for CGI/Perl scripts - if your script does not work or you get an "Internal Server Error" when you run it try this first.

To change file permissions using your FTP software:

1. Download an FTP software like CuteFTP, WS_FTP, or Filezilla.

2. Log into your account and go to the directory where the files are located.

3. Highlight the file or directory that you want to change permission.

4. Locate the "file permission" or "chmod" command on your FTP software (you may need to refer to the manual/help file or right click on the filename with your mouse)

There should be three groups. Each group should have either checkboxes or a selection for the permission type.

1. set pages to rw- for the owner, no permission for the group, and r--for other

2. set scripts to rwx for the owner, no permission for the group, and r-x for other

3. set data/config files to rw- for the owner, no permission for the group, and rw- for other


To change file permissions using your Control Panel - File Manager:

1. Log into your account Control Panel (mydomain.com/cpanel), go to the File Manager, and then the "WWW" or "public_html" folder.

2. Identify the file that you want to change permission by clicking on the file/directory link.

After selecting the link the right menu will update itself and show you a list of things you can do to the file/directory. At this point select "Change Permissions. A box like below will load:

There should be three groups. Each group should have checkboxes for the permission types.
Definitions: (User=Owner, Group=Group, World=Other/Public)

1. set plain html pages to rw- for the user, no permission for the group, and r--for world (default)

2. set scripts to rwx for the user, r-x for the group, and r-x for world

3. set data/config files to rw- for the user, no permission for the group, and rw- for world

Select "Change" to finish.

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