Re: [gentoo-user] sudo echo cannot write to /etc/ files ?

[David Morgan]

On 15:52 Wed 06 Jul     , Holly Bostick wrote:
> Hey, ho--
>
> Here's (one of) today's non-critical problems that's getting on my
> nerves, so hopefully somebody can help.
>
> I've finally got around to setting up sudo. It works fine, except for
> one thing.
>
> I don't just give myself blanket permissions to sudo to all commands; I
> made a Cmd_Alias group which includes a lot of utility apps. And, like
> many of you, I included emerge in this group.
>
> But a lot of the time, when I do an emerge -av, I find that there's a
> USE flag I want or don't want for the package, or I want an unstable
> version, or whatever, which means I have to echo to one of the files in
> /etc/portage.
>
> Echo is in the sudo-ed group, and echo isn't the problem-- the problem
> is that permission is refused to write to the file itself (which is an
> error *from* echo, so it would seem that echo itself is OK as far as
> sudo goes). Which means that I have to su anyway, to echo to the file,
> which really isn't the point of the exercise.
>
> As I see it, this error can mean only one of two things:
>
> sudo does not give me a login shell (so my UID is 'really' still my UID
> and not root's, and I don't have permission to write to the file); or
>
> there is another, "invisible" cli utility responsible for actually
> writing to the file, which is not sudo-ed.
>
> Or could it be something else?
>
> In any case, does anybody know how I could fix this? It's really
> screwing up my useability, which was just starting to shape up nicely :-) .
>
> Thanks,
> Holly
>


I assume you mean that you're trying to something like

sudo echo foo >> bar

The problem is that echo is running as root, but >> (a shell builtin)
isn't. Your shell evaluates the >> before it does anything else, so you
get permission denied if you aren't allowed to write to bar. (Think
about what happens if you do 

cat foo > foo

you end up with foo being empty regardless of what was in it before you
ran the command (actually, that command fails with an error about the
input and output files being the same, but I'm pretty sure that what I
said used to be true)).

Someone else asked the same question on this list not long ago, and the
only solution I remember anyone having was to run

su -c "echo foo >> bar"

Dave

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