Re: chmod failed: Invalid argument

[Rainer Blome <rainer.blome@gmx.de>]

On 28.01.2016 21:40, Corinna Vinschen wrote:
> On Jan 28 19:43, Rainer Blome wrote:
>>> Corinna Vinschen wrote 2016-01-28 18:22:
>>>> On Jan 28 17:06, Rainer Blome wrote:
>>>>> Corinna Vinschen wrote 2016-01-28 15-44: And then, what about
>>>>> this unknwon group with gid 213?  What does
>>>>> 
>>>>> $ getent group 213
>>>>> 
>>>>> print?  Something's weird here...
>>>> 
>>>> getent group 213; echo $? # getent prints nothing, returns 2
>>>> 
>>> On a hunch, do you have old /etc/passwd and /etc/group files by
>>> any chance?  Does moving them out of /etc (don't delete them for
>>> now!), exiting from Cygwin and starting a new shell somehow fix
>>> things for you? How do the files look like?
>> 
>> Define "old"! ;-) Yes, I do. There is no `/etc/group`, but 
>> `/etc/passwd` defines the group ID of my user as 213 (the real ID
>> is a bit different, to be honest, but I do not think that 
>> matters.)

The real group ID is 513, by the way. On a Cygwin 2.3.1 on a different
machine, `/etc/passwd` also has 513 in the group column of all users.
Yet, when I ask for `id`, I get something like this (translated):

 uid=197609(username) gid=197121(None) \
  Groups=197121(None),545(Users),...

> Ouch, that may be the reason.  I have to check that but your passwd
> and group files are
> 
> 1) Not required anymore, see 
> https://cygwin.com/cygwin-ug-net/ntsec.htm, and

Well, I do not use Active Directory, and I try to maintain a stable
home directory across new machines, drives or Windows reinstalls,
so I specify this directory in `/etc/passwd`. Since it is small,
I see no harm in using this method.

On my Cygwin 2.4.1, to get things to run the way I want them, I
renamed `/etc/passwd.renamed` back to `/etc/passwd`, and replaced
the old group id by the ID of group "None", 197121.
In a new terminal, things now run as expected, SSH finds its .ssh
directory and `chmod` etc. work the way that they should.

> 2) *iff* they are there, there's good reason to have them in a good
> working shape.

No doubt. So what kind of maintenance do these files need?
Should I have known that they do?

>> The `git clone repo:bar` then fails because my `~/.ssh` is 
>> apparently no longer found (and I can only log in via SSH key). 
>> This is a bit surprising, because in the new terminal, `$HOME` and
>> `~/.` are still set the way I specified it in the old `/etc/passwd`
>> (now with extension `.renamed`).  So some programs apparently use
>> one method of determining the home directory, and others use a
>> different method. I will look into that tomorrow.
> 
> Yes, indeed.  Ssh ignores $HOME and it does so as long as it exists.
> Ssh uses the pw_dir field from your passwd entry and that in turn is
> determined by /etc/passwd if it exists, or by /etc/nsswitch.conf. See
> the extensive documentation starting at 
> https://cygwin.com/cygwin-ug-net/ntsec.html#ntsec-mapping-nsswitch 
> The default homedir is /home/<USERNAME>.  There are a few knobs to 
> play with to change this setting, see 
> https://cygwin.com/cygwin-ug-net/ntsec.html#ntsec-mapping-nsswitch-home

In the User-specific Windows environment variables, `$HOME` was
set, so that most programs still saw that. To simplify, I removed
that setting, hoping I did not use it in some Windows batch file. :-)

>> If, after this "breakthrough", there is still value in looking 
>> further into the ACLs, I am willing to do that.
> it might not be required anymore to generate the strace at all.

Then I'll skip that for now. Maybe a bogus group setting in
`/etc/passwd` is enough to reproduce the issue.

>> Thanks for the help so far.
> 
> Thanks for *your* help.  I expect there are still a few problems in
> that code since not even a multi-month testphase finds all problems.

I am curious what change triggered the issue, can you point me to a
commit or change-log entry?

Rainer

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