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Re: Error on /bin/sh -login: "cannot remove /bin/sh.exe: Permission denied"


Webb Roberts <webb.roberts <at> gtri.gatech.edu> writes:

> 
> I just updated my cygwin install.
> 
> on running /bin/sh -login, I got the following message:
> 
> /bin/cp: cannot remove `/bin/sh.exe': Permission denied

Not the nicest thing to have a random error message appear on stdout
during a login, especially if it would interfere with ssh or other
remote protocols.  But you at least still have a working /bin/sh
(albeit out-of-date, or the error wouldn't have printed).

> 
> Looks like the error is coming out of /etc/profile.d/00bash.sh: the part 
> where it's trying to update /bin/sh.exe via a copy in the midst of 
> running profiles:
> 
> /bin/cp -fpuv /bin/bash.exe /bin/sh.exe 2>&1 >> /var/log/setup.log.full

Bah - and I'm the bash maintainer, so I should know better when writing
a shell script!  Not only that, but I've corrected other people on this
very list for doing redirections in the wrong order!  [/me goes and
crawls in a hole]

> 
> 1.  Isn't it a little strange to have this done on user time every time 
> users run profiles?

No - because once the update has been done successfully, /bin/sh is no
longer out of date, so the profile script short circuits without any
further attempt to update /bin/sh.  Once up-to-date, the time spent by
/bin/test to check timestamps on every user's login is minimal compared
to the time wasted on this list for bug reports that /bin/sh was
altogether missing when people had upgrade problems that prevented the
bash postinstall script from running.

> 2. If the redirect and the file append were reversed, I'd never see the 
> error; it would go straight to the logs.  As it is, nothing goes to the 
> logs.

Yep.  And the next release of bash (expect it in the next day or two)
will fix this heinous bug.

> 3. Once I killed all my /bin/sh processes, and ran /bin/bash -login, the 
> copyover happened OK.

Yep - Windows won't let you replace an in-use file, which is why you
were getting permission denied errors on subsequent shells.  When you
upgrade a cygwin installation, it is MUCH better if you don't have any
cygwin processes, including /bin/sh, running at the time.

>  I'm just a freak trying to stick to sh.

But in cygwin, /bin/sh IS bash (by default).  The only difference is that
bash turns on POSIX behavior by default when invoked as sh instead of bash.

> 4. Should this code be running when I'm under /bin/sh?  Looks like it's 
> bash-specific; I'd expect the default profile code for sh to be sh-specific.

The code should be run for EVERY bourne-style login shell (sh, ash, bash,
ksh, pdksh, zsh), because experience has shown that cygwin without
/bin/sh installed is pretty much broken (think system(2), for example).
In fact, I might even try to make a counterpart 00bash.csh profile script
that runs for a tcsh login shell, now that I think about it.  When cygwin
swapped from /bin/sh being ash to being bash, I wanted to make sure that
everyone has a working /bin/sh.  But I also wanted to make sure that
advanced users who don't want bash as their /bin/sh (for whatever reason)
can have their wish too, by touching /bin/sh to have a timestamp further
out into the future so that the upgrade script will not attempt to install
bash in place of whatever shell you prefer as your own /bin/sh.

I will also try to clean up the profile script to short-circuit when you
are running /bin/sh instead of /bin/bash (obviously, if you are in sh, it
is not missing, which is the worst problem the profile script tries to
prevent; and since attempts to upgrade it must fail, all I can do is
let you be aware that your /bin/sh may be out-of-date).

> 
> Thanks!
> Webb

Thank you for catching the bug in my postinstall script.

-- 
Eric Blake
volunteer cygwin bash maintainer



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