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jpp1
Asked: 2023-02-20 20:37:26 +0800 CST

sshfs option idmap=file prevents mounting entirely without error message

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We want to use sshfs to mount directories from a server on a client, bit some user and group ids do not match between those machines. The requirement is that user ownership is mapped correctly and the client is able to change the group of files to those groups where the local and remote user have the appropriate permissions.

After testing that sshfs HOST:DIR MOUNTPOINT -o idmap=user works and mounts the directory properly (but obviously does not map the user and group ids correctly) I tried sshfs HOST:DIR MOUNTPOINT -i idmap=file,uidfile=uidfile,gidfile=gidfile with the proper content of uidfile and gidfile.

This then does not mount anything at all, and also does not show any error message either on the console or in the logs!

When running the command with the debug option -d, one can see that the command exits with exit code 1, doing everything the command which uses idmap=user does in exactly the same way.

I tried this on several machines, with the same frustrating result on all of them.

ssfhs version is 3.7.1

It is hard to believe that such a blatant bug is the software and apparently not documented - is there anything known about this, any workaround?

sshfs

1 Answers

  1. Best Answer

    After some investigation, this happens if:

    • the nomap parameter is not added or set to nomap=error
    • either or both of the gidfile or uidfile contain something or lack something sshfs needs, e.g.:
      • a group which is in the mount is not mapped
      • the main group of the user is not mapped
      • a mapping contains a group id which is not settable by the user
      • unknown other conditions

    In all those cases sshfs silently quits without any error message and without any indication what exactly causes the problem and which file is to blame.

    So the bug is really that in all those error sitations, sshfs does not show any message on the console or the log and just silently quits.

    See https://github.com/deadbeefsociety/sshfs/issues/6

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