Using SSH Transfer Client (v. 3.2)
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Permissions Redux


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Understanding Access Permissions

Access permissions will make or break your web-publishing experience. If you understand them, your life will be much easier. Basically, you want certain things to be viewable by others, and some things you don't. Everything in your public_html folder should be pulicly accessible...otherwise, perhaps it shouldn't be in that folder. Yes, you can and should store files in your account space that aren't webpages and pictures. You can put anything there that you want...for instance, the paper that you were writing late in the lab. Make sense? Read on!

Step 1:
Access permissions apply both to folders and to files. For instance, your public_html folder should have a numerical access value of 755. What does that mean, exactly? OK...there are three types of users that can potentially access your files. You are one of them. You are the "owner". Groups of people, such as your classmates, can have special access privileges...they are called "group". And last...there is a user group called "other". These could be people trying to view your webpages from their home computers.

Step 2:
Each user group is a ssigned a numerical access value. Let's take, for example, a numerical access value of 755 (for your public_html folder above). The number 7 corresponds to the "owner" (i.e. you). The next 5 corresponds to "group". And the last 5 corresponds to "others". Get that? Owner(7)/group(5)/other(5)=755 (in this case). So what do the numbers represent?

Step 3:
Each number is a sum of other numbers which correspond to individual types of access. Take a look at the following table for an explanation.

Permission Type Numerical Value
Execute permission 1
Write permission 2
Write and execute 3
Read permission 4
Read and execute 5
Read and write 6
Read, write, & execute 7

"Read" means that any user group with that permission can view the file or the contents of the folder. "Write" means that they can modify the file or the should be careful when granting write permission. "Execute" means that they can run any program contained within a particular folder or within any particular file.

So, for the value of 755 the owner had a numerical permission value of 7 because he/she has "read", "write", and "execute" permission (and because 4 + 2 + 1=7). Make sense? What's the value for "group" and "other"? They both have a numerical permission value of 5 because they have "read", not 'write", but do have "execute" permissions ( and because 4 + 1=5).

Step 4:
In the SSH Transfer Client window (in the remote view) you can view your permissions for each individual file and folder. In the toolbar...change the display type of the remote view to "Details" by clicking that button. In this view, you can see the permissions corresponding to each file/folder on the right side of the remote window. See the following screenshot for an example.

Permissions Screenshot

Step 5:'s obvious that there aren't numerical values in the right column where the permissions are displayed...but there is a rhyme to the reason. If you view details for the public_html folder in this example it should make sense. Much like the individual numbers that make up the numerical value 755, the permissions detail as shown here can be divided up by the three user types owner, group, and other (other is sometimes refered to as "world"). The "d" at the beginning of the string simply stands for directory (or what many people call folders...the two are interchangeable). In the case of files...the absence of the "d" means that it's a file.

So what's this rwx stuff? Well, it's quite simple actually. r=read, w=write, x=execute. We already saw what numerical value each permission had...the long string (e.g. for public_html) is drwxr-xr-x. A dash (i.e the absence of any permission be it r, w, or x) means that the user group does not have that particular permission. In this case, neither group nor other has write permission. Take the three-column metaphor one step further and it all should come together.

Permissions further explained

Bringing it all together is the next table of corresponding values.

Directory? Owner
  7 5 5
d rwx r-x r-x
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© 2003 Chad Hutchens | iSchool | UT Austin | webmaster