Why is group 'users' (gid 100) immutable? I need to use it

TrueNAS General
1

I am migrating data to a new TrueNAS storage system and am creating user and group credentials for my users. However, TrueNAS has pre-defined group “users” with GID 100 and made it unusable (immutable). And then it has provided “builtin_users” with GID 545. But because I am migrating data that will be exported by NFS, I need to preserve UID/GID information. How can I use GID 100?

Thank you.

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Admittedly this is not an area I am well versed in, so take this for what it is, an amateurish comment.

You should not try to use GID 100 on the TrueNAS side. Doing so will cause you issues.
Instead, look at NFSv4 idmapping as a form of translation layer.

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Thanks for the suggestion Neo. I think you have put me on the right track. If I use idmapd, then the username (and I assume its login group name) that is used for authentication is mapped to the local uid and gid for NFS.

That sounds straight-forward enough in principal but I don’t yet see how to do this via TrueNAS’s management. I would have expected some configurable settings for Services→NFS and also for each NFS Share. The closest I can see is “Manage Groups Server-side” under Services→NFS.

I will dig into this further. Thank you for your help.

4

At the end of the day, I gave up and decided to rework file permissions using chmod & chown once the files were copied over. The QNAP provides very pared down services and I worried that it would somehow cause grief to idmapd or NFS. These files are either for myself alone or for sharing with family members. That means it’s a pretty finite number of ownerships to reset.

This brought to mind some old memories. In 1987, I was part of the team that migrated our in-house development tools from VM/CMS (Big Iron) to Unix. As such, I was one of the very first LDAP Unix users created and my UID was 43. (Only UIDs 0-32 were “reserved” at that time.). As the years went by this never caused any operational problems, even when the reserved UID range expanded, but eventually, decades later, the central IT organization forced me to change it. As a form of consolation, they gave me UID=55555 but it still caused quite a bit of work for the IT group because it invalided an enormous number of files on many enormous NFS project disks, not to mention archives.