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The basic command for changing
file permissions in unix based operating systems is the
'chmod' command. This command is executed with a set of
parameters after it. With most FTP clients, you can simply
select the filename you want to change the permissions of,
right click, and choose the chmod command.
There are three main groups
of permissions when dealing with the chmod command. The
three groups are yourself or owner, your unix group, and
everyone else. A typical chmod command would look like
this - 'chmod 755' This allows you to add, remove or
rename files as well as read or edit a file. It also
specifies that your unix group and everyone else can only
read and edit the file in question. They can't add,
delete, or rename the file.
How the numbers in the
chmod command work
There are three types of
permissions that can be given to a file. They are read,
write, and execute. The read permission is assigned a
value of 4, the write permission is assigned a value of 2
and the execute permission is assigned a value of 1. So
when a chmod command specified the digit 7 as the first
number, it means that all three types of permissions are
to be assigned to it. If a party is assigned a value of
'0' then it means it has no rights whatsoever to a file.
'6' tells the server that the user can read and write to
the file but can't execute it. I think you get the idea.
Common permissions to set
Most of your html files
will do fine with a permission of 644. Most script files
will need a permission of 755. Any configuration files in
a script package will often need a file permission of 777.
Be very careful about assigning a file permission of '777'
for everyone. With this permission, it means that anyone
who gains access to your server will be able to add,
remove, rename, read or edit the file. It is always a good
idea with security in mind to assign the least amount of
permissions necessary to get the job done.
An FTP client can keep
things simple
Most people on shared
servers will not have access to a command line to be able
to use the chmod command. For most people, changing file
permissions will be done through an FTP client. To do
this, right click on the file you want to alter, and
choose the chmod command. You will usually get a popup
that will show nine checkboxes. The will be arranged in
three rows. On the left you will usually see Read, Write,
and Execute for the row headings. You can accomplish the
same thing as typing in the numbers above by clicking on
one, two or three boxes for each party. Once you're done,
you click the apply or ok button and the file permissions
will be changed.
If you keep in mind that
you need to always go with the most restrictive file
permissions possible that still allows your files to
execute, and that there are three parties to define
permissions for, you'll do fine. The three parties again
are the owner, group, and everyone else.
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About
The Author
This
article was written by Joe Duchesne,
president of http://www.yowling.com/,
a web hosting company that specializes in
helping online business owners increase
their website traffic. Copyright 2004
Yowling. Reprint Freely as long as you
link back to my website from this resource
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