RE: Being denied my own files!

In order to delete the file, you must:
* have write access to the file
* have write access to the directory
* the sTicky bit (chmod +t) must not be set on the directory (sTicky is
rare)


-----Original Message-----
From: fedora-desktop-list-bounces(a)redhat.com
[mailto:[e-mail]] On Behalf Of Dotan Cohen
Sent: Thursday, March 10, 2005 5:09 PM
To: fedora-desktop-list(a)redhat.com
Subject: Being denied my own files!

When trying to delete a file in my /home/dotancohen directory (and
logged in as dotancohen) I get:

Access denied to /home/dotancohen/ankush.jpg.

In rightClick-> Properties-> Permissions I saw that Owner can read and
write, Group can read, and Others can read. So I changed the
permissions so that all the groups say read & write, but still I
cannot delete the file. No other application is accessing the file.
I'm using Konqueror in KDE on FC3. Thanks in advance.

Dotan Cohen
http://English-Lyrics.com
http://Song-Lyriks.com

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[OT] RE: Being denied my own files!

[Nils Philippsen]

Besides being off-topic (fedora-list would be on-topic for this
question), ...

On Thu, 2005-03-10 at 17:12 -0800, Miller, Marc wrote:
>  In order to delete the file, you must:
>  * have write access to the file 
no. I can delete root-owned files in my directories even if I don't have
any rights on the files themselves.

>  * have write access to the directory
>  * the sTicky bit (chmod +t) must not be set on the directory (sTicky is
>  rare) 
No. The sticky bit on a directory specifies that contrary to the above
only file owners can delete their files, handy for world-writable
directories like /tmp and /dev/shm.

Nils
-- 
     Nils Philippsen    /    Red Hat    /    nphilipp(a)redhat.com
"They that can give up essential liberty to obtain a little temporary
 safety deserve neither liberty nor safety."     -- B. Franklin, 1759
 PGP fingerprint:  C4A8 9474 5C4C ADE3 2B8F  656D 47D8 9B65 6951 3011

[OT] RE: Being denied my own files!

[Miles Goodhew]

Hi,
  The magic of Unix inodes:

    No user can _actually_ delete a file (Not even root)!

  However, If a user can write to a directory (and root can write to
any local directory not on a read-only filesystem), then that user can
delete the link to the file (i.e. delete the file's name from the
directory). If a file's link count (= number of directories the file
has a name in) and the number of references (= number of open file
descriptors for the file) both go to zero, then the system deallocates
the files data blocks and makes the file's inode (which is the unique
head of a file) reusable for new files.

Exercise:

% echo "This is the first file" >file1
% ln file1 file2 # Do _not_ put a "-s" here!
% ls -li file?

  The inode number is the first column - file1 and file2 have the same
inode -> they're the same file (just two different names for it - the
inode and all data blocks on disk ate the same thing). The link count
is the column after the mode bits - it's has the value 2 indicating
that the file has two names.

% rm file1
% cat file2

  Hmm, look familiar?

Bonus brainteasers:
* How many links does "/" have? Why? What are ".." and "."?
* What's a symbolic link.
* What do "chmod g+s" and "chmod u+s" do to files/directories (This
can be fun on Sunos!)

Moles.

-- 
Miles Goodhew, Senior Hacker
TransACT communications

[OT] RE: Being denied my own files!

[Kyrre Ness Sjobak]

>  no. I can delete root-owned files in my directories even if I
> don't have
>  any rights on the files themselves. 
Strange. I have experienced several times to delete something root-owned
(in my home folder) from nautilus -> get thrown to ~/.Trash. (or
media/trash, but removable media is usually vfat so permissions isn't an
issue)

When i then try to empty trash, all i get is "acess denied".

[OT] RE: Being denied my own files!

[Miles Goodhew]

Kyrre,


On Fri, 11 Mar 2005 21:09:28 +0100, Kyrre Ness Sjobak
<kyrre(a)solution-forge.net&gt; wrote:
>  Strange. I have experienced several times to delete something
> root-owned
>  (in my home folder) from nautilus -> get thrown to ~/.Trash. (or
>  media/trash, but removable media is usually vfat so permissions isn't an
>  issue)
>  
>  When i then try to empty trash, all i get is "acess denied". 
  If you own a directory, or if you have write permission to it, you
can modify all links (file names) within it. If root owns any "normal"
file in the dir, you can delete them immediately (rather, "unlink"
them - only the system can delete).
  However, you can't unlink a directory file (yes, at the inode level,
everything's a file with a specific type) unless the directory only
contains the two links/names "." and ".." ("self inode" and
"parent
inode").
  So it follows from the preceding two paragraphs that if root owns a
directory in your home directory (and you can't write to that
directory), then you can move it to some other directory (say
"~/.trashcan" or something similar), but you can never actually
crowbar it out of the filesystem.

  In that final case (and if you don't actually have root access to
the box you're using), I usually move the directory as far up the
filesystem as I can (put it in "/tmp" if it's the same filesystem),
rename it to something like "FOR_CLIFFS_SAKE_DELETE_ME" and then
possibly send the owner an email requesting it be expunged).

Moles.

-- 
Miles Goodhew, Senior Hacker
TransACT communications

[OT] RE: Being denied my own files!

[Kyrre Ness Sjobak]

søn, 13.03.2005 kl. 13.17 skrev Miles Goodhew:
>  Kyrre,
>  
>  
>  On Fri, 11 Mar 2005 21:09:28 +0100, Kyrre Ness Sjobak
>  <kyrre(a)solution-forge.net&gt; wrote:
>  > Strange. I have experienced several times to delete something root-owned
>  > (in my home folder) from nautilus -> get thrown to ~/.Trash. (or
>  > media/trash, but removable media is usually vfat so permissions isn't an
>  > issue)
>  > 
>  > When i then try to empty trash, all i get is "acess denied".
>  
>    If you own a directory, or if you have write permission to it, you
>  can modify all links (file names) within it. If root owns any "normal"
>  file in the dir, you can delete them immediately (rather, "unlink"
>  them - only the system can delete).
>    However, you can't unlink a directory file (yes, at the inode level,
>  everything's a file with a specific type) unless the directory only
>  contains the two links/names "." and ".." ("self inode" and
> "parent
>  inode").
>    So it follows from the preceding two paragraphs that if root owns a
>  directory in your home directory (and you can't write to that
>  directory), then you can move it to some other directory (say
>  "~/.trashcan" or something similar), but you can never actually
>  crowbar it out of the filesystem.
>  
>    In that final case (and if you don't actually have root access to
>  the box you're using), I usually move the directory as far up the
>  filesystem as I can (put it in "/tmp" if it's the same filesystem),
>  rename it to something like "FOR_CLIFFS_SAKE_DELETE_ME" and then
>  possibly send the owner an email requesting it be expunged). 
Okay, i understand :)

Isn't /tmp often flushed by a reboot etc, also?