Re: [gentoo-user] Root can't write to files owned by others?

[Jack]

On 2022.03.09 13:28, Dr Rainer Woitok wrote:
> Greetings,
>
> until recently my system behaves sort of strangely:
>
>    $ touch /tmp/file
>    $ ls -l /tmp/file
>    -rw------- 1 rainer rainer 0 2022-03-09 19:06 /tmp/file
>    $ echo x | sudo tee /tmp/file
>    Password:
>    tee: /tmp/file: Permission denied
>    x
>    $ chmod a+w /tmp/file
>    $ ls -l /tmp/file
>    -rw--w--w- 1 rainer rainer 0 2022-03-09 19:06 /tmp/file
>    $ echo x | sudo tee /tmp/file
>    tee: /tmp/file: Permission denied
>    x
>    $
>
> Since when can't root write to files  it doesn't own?   And not even,
> if
> the file has write permission for everybody?
>
> This worked as long as I can think of.  My last routine upgrade
> install-
> ed new  kernel package  "sys-kernel/gentoo-sources-5.15.26",  so I
> built
> the new kernel and booted from it.  May this be the reason?
>
> When I'll have time to reboot,  I'll test the  above commands  on my
> old
> kernel, 5.15.19.  But perhaps there's another reason?
>
> Slightly puzzled
>      Rainer
Just a gues, but try something like 'sudo -c "echo x | tee /tmp/file"'  
or just su first and then do the echo and tee.  I think perhaps the  
permission error is not for root writing to /tmp/file but for the echo  
x trying to write to a tee owned by root.