File permissions?

[Tim Frost]

Jim,

The reply from Fred Roller may shed some light.

Ubuntu uses 'sudo xxx' to do 'xxx' as root.  You may need it here.  When
sudo asks for a password, supply *your* password

On Thu, 2009-12-24 at 21:09 -0600, Jim Byrnes wrote:
> I've been using Ubuntu for about two weeks now and am starting to get 
> used to it.  However, coming from an OS/2\Windows world file permissions 
> seem to be giving me some grief.
> 
> Maybe if someone could tell me how to do a couple of specific tasks it 
> would become clearer to me.  I have Jedit loaded on all three of my 
> OS's. I have modified some mode files on the other OS's I would like to 
> use on Ubuntu.  I copied them to a shared folder on Ubuntu but I can't 
> copy them to /usr/share/jedit/modes which is where Jedit will look for them.

Most packages support a per-user settings location, in the user home
directory.  For jedit, this is the directory $HOME/.jedit, which you
own.  If you put the customised modes in directory $HOME/.jedit/modes,
you should have them accessible to you, and you can modify them safely.
This makes them available to you, but not to other users on the Ubuntu
system.

To make them available to other users, you need to install the modified
files in /usr/share/jedit/modes.  Rules for directory permissions are
more complex than for files:
* To create or delete a FILE in the directory, I need WRITE permissions
on the directory (not the file - but rm will warn if I try to remove a
file I can't write to)
* to edit a file, I need read/write permissions on the file, but not the
directory.
(This is because of the way that linux/unix stores permissions and
ownership information)

If you need to put the mode files into /usr/share/jedit/modes, the
following will allow you to do that:
  sudo cp -p <my-mode-files> /usr/share/jedit/modes

Using sudo will allow the copy to change the permissions, and add new
files into the directory. The '-p' option will preserve permissions
(including the fact that you own the files) when copying them.  This
means that you should have the modified files available for all users,
and you should be able to update them (including copying replacements
from the other computers) without needing to use sudo [unless you want
to modify a file that you don't yet own on the ubuntu machine).


> 
> In that same vein, if I wanted to edit one of those files with Jedit how 
> could I get Jedit to open it for editing?

You can give yourself the ability to edit all of the files in the
directory /usr/share/jedit/modes, with
  sudo chown $USER /usr/share/jedit/modes/*


> 
> Thanks,  Jim
> 

One caveat here:
Because the files in /usr/share/jedit/modes are part of the jedit
package, you may find that they get overwritten when you use the package
management system to upgrade jedit.  For that reason, it is safer to use
$HOME/.jedit/modes, which won't be touched by a package upgrade.

Tim


-- 
Tim Frost <timfrost at xtra.co.nz>
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