[ubuntu-uk] Help needed with ssh

Alan Lord (News) alanslists at gmail.com
Fri Jul 17 07:16:21 BST 2009

On 17/07/09 06:45, John Matthews wrote:
> Ok, this is some good news, I have a question to ask, I need to change
> the permissions of a file in one of my folders, on my site, it has to be
> read only, as it is its 777.
> I have gotten into the folder and have the list of files and their
> permissions, and I can see the file I need to change, but I am not sure
> of the command.
> I know you have to chmod to something but I cannot work it out.
> Can somebody help please?

chmod is the right command but, depending on who *owns* the file you 
might not have permissions to do so straight away.

man chmod will help you. There are several ways to achieve the same thing.

essentially the command is:

chmod [OPTION]... MODE[,MODE]... FILE...



Personally I prefer the octal method.

Your file has three sets of permissions

-rw-r--r-- 1 alord alord 49 2009-05-13 19:43 temp

(BTW, this information is well documented in several of the links we 
supplied previously).

Ignoring the very first (from the left) "-" you should see three groups 
of "---" Which in my case show

rw- (The File Owner: The first alord you see)
r-- (The Group Owner: The 2nd alord)
r-- (Anyone/Everyone: Also referred to as World)

So, who do you want to have read only access? Everyone but you? Everyone 
but you and the group? Or Everyone?

chmod 444 filename

Will set all three sets of permissions to Read only.

chmod 666 filename

Will set all three sets of perms to Read/Write.

chmod 555 filename

Will set all three perms to Read/Execute

You add up three numbers to get the right one:

1: Execute,
2: Write,
4: Read.

If you want the file to be read only for everyone else, but *you* (The 
file's owner) needs read/write then do:

chmod 644 filename

You do not say what or who owns the file. If it on your webserver, it 
might be owned by the web-server perhaps? Sometimes called www-data, 
apache, nobody or httpd. The name is [almost] arbitrary but if it isn't 
the same as your username you do not own it.

If you are not the owner you might not be able to change it without 
becoming root or assuming root privileges by using sudo (if available on 
your system).

This page (of the link I have referred you to on several occasions) will 
explain all this far better than I can in a text-mode email.



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