GNU bug report logs - #21713
On CIFS, mv behaves as mv -f

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From: Pádraig Brady <P <at> draigBrady.com>
To: Sam Kuper <sam.kuper <at> uclmail.net>
Cc: 21713 <at> debbugs.gnu.org
Subject: bug#21713: On CIFS, mv behaves as mv -f
Date: Mon, 19 Oct 2015 18:37:34 +0100

tag 21713 notabug
close 21713
stop

On 19/10/15 18:30, Sam Kuper wrote:
> On 19/10/2015, Pádraig Brady <P <at> draigbrady.com> wrote:
>> On 19/10/15 13:49, Sam Kuper wrote:
>>> On a system where `df -T` shows the file system to be "cifs"
>>> (presumably the Common Internet File System from Microsoft:
>>> https://technet.microsoft.com/en-us/library/cc939973.aspx ), running
>>> `mv` causes unexpected behaviour. Essentially, `mv` behaves as though
>>> `mv -f` had been used.
>>>
>>> Example, using GNU Coreutils 8.21 on Ubuntu 14.04.3 LTS:
>>>
>>> $ which mv
>>> /bin/mv
>>> $ ls -l
>>> total 0
>>> $ echo foo > 1; chmod -w 1; cp 1 2; ls -l | cut -d' ' -f 1-5,9
>>> -r-x------ 1 me me 4 1
>>> -r-x------ 1 me me 4 2
>>> $ echo bar > 2
>>> -bash: 2: Permission denied
>>> $ mv 1 2
>>> $ ls -l | cut -d' ' -f 1-5,9
>>> -r-x------ 1 me me 4 2
>>>
>>> I would have expected the `mv 1 2` command to have prompted the user
>>> before overwriting file 2. It would be helpful to the user if mv could
>>> be improved so that it behaves as expected, even on a "cifs" file
>>> system.
>>>
>>> For comparison, running the same commands on a machine with an ext4
>>> file system and a recent version of Coreutils yielded:
>>>
>>> $ mv 1 2
>>> mv: replace ‘2’, overriding mode 0444 (r--r--r--)?
>>>
>>> as expected.
>>>
>>> N.B. I first mentioned this issue at
>>> http://unix.stackexchange.com/q/237123/6860 and am grateful for the
>>> helpful feedback from the people who commented there, which helped me
>>> identify the file system as the likely confounding factor.
>>>
>>> Thank you for maintaining Coreutils!
>>
>> I guess that's the write bits being ignored or mapped to another meaning on
>> cifs?
>> I.E. access(..., W_OK) is returning OK (0) for you?
>> You can check this like: strace -e access mv 1 2
> 
> BEGIN TEST
> 
> $ ls -l
> total 0
> $ echo foo > 1; chmod -w 1; cp 1 2; ls -l | cut -d' ' -f 1-5,9
> -r-x------ 1 me me 4 1
> -r-x------ 1 me me 4 2
> $ strace -e access mv 1 2

> access("2", W_OK)                       = 0
> +++ exited with 0 +++
> 
> END TEST

Right, so the file system is saying we can write to that file,
so not an issue with coreutils, rather a limitation of cifs,
or your cifs setup.

thanks,
Pádraig.

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