mongodump "too many positional options have been specified on the command line"

[Yaron]

I can't run the mongodump utility in Ubuntu (from the internal packages).

Running without any parameters works BTW.

I tried running a dump this way:
mongodump -u xxxx -p xxxx --host somehost.com:27017 -d some_db -o backup

And I got this reply:
Error parsing command line: too many positional options have been specified on the command line
try 'mongodump --help' for more information

Then I purged the package using:
apt purge mongodb

And then added the official mongo repo as explained on the mongo website:
https://docs.mongodb.com/manual/tutorial/install-mongodb-on-ubuntu/

Ran the same command again and voila! it worked.
I tried search for the "too many positional" error and found out it might have something to do with some problematic minus or em-dash/en-dash but it's not the case because I wrote everything manually and the same command exactly worked with the official mongodb-org by mongo.

[Nish Aravamudan (nacc)]

Hello and thank you for filing this bug report.

Note that the `mongodump --help` output states:

  -h, --host=<hostname> mongodb host to
                                                            connect to
                                                            (setname/host1,host-

Have you tried:

mongodump -u xxxx -p xxxx --host=somehost.com:27017 -d some_db -o backup

?

As far as I can tell, mongodump has no positional arguments, so it's rather confusing.

I am unable to reproduce the issue, in any case, on 17.04 (with or without '='). What version of Ubuntu are you running?

[Yaron (sh-yaron)]

16.10.

If it's solved up simply upgrade my Ubuntu version.

[Nish Aravamudan (nacc)]

Ok, I have reproduced the issue on 16.10 and it does seem fixed on 17.04. While, I agree you can upgrade, 17.04 is beta still and we should fix it properly (especially if 16.04 is also affected). Let me debug it a bit further and see if we can't get a fix out soon.

[Nish Aravamudan (nacc)]

It does seem that mongodump has been rewritten in the first in 17.04 in go. So I think both 16.04 and 16.10 are affected, but not 17.04. I am working on testing a fix to the source still.

[Nish Aravamudan (nacc)]

Note that skipping the space between -p and the password seems to work here. I don't know why yet.

[Yaron (sh-yaron)]

@nacc peculiar, this is the only change you've made to the arguments?

[Nish Aravamudan (nacc)]

Yes, that's right. Alternatively, you can just pass -p and it will prompt for the password.

If I had to guess, this is a buggy implementation of the code to elide the password from the comm of the process (so you don't see it in ps aux, I think). I wonder if it doesn't recognize the space between -p and the password, so it treats the password as a positional argument.

Oddly, if I build the same source without the flags we pass during the .deb build, I don't get this behavior.

While annoying, there is an easy workaround for now.

[Nish Aravamudan (nacc)]

Alternatively, we can at least update the help and manpage to document the behavior.

[Nish Aravamudan (nacc)]

I don't know that we will fix this in 16.04 -- it's a low priority issue with a pretty easy workaround. Just an FYI.