Aufs, observations and notes

1. offizieller Beitrag

    Hey guys, just wanted to relay some experiences and notes I've learned about Aufs whilst troubleshooting my system here.


    Currently my home setup consists of 11 drives (with space for 13) of varying degrees of space and reliability. I set up SnapRaid and a few media sharing systems and decided on Aufs as my drive pooling solution.


    All was well and good, but I noticed after a while that some folders I dumped into drone factory were failing, or a comics folder dumped into a general share wasn't accessible. I deleted the folder, but alas it was still there somehow! That, coupled with weird permissions problems prompted me to dig deeper. I enlisted the help of a friend, together we granted a user account ownership of a test file and chmodded it to 777, got onto Putty and then flicked over to it. We could see the file, we could write another file in the same directory but alas renames or anything just weren't working.


    It turns out Aufs just says that it's changed the permissions, on the drives themselves the permissions remain the same. At least in my case, I've also noticed that deletes are a bit hit and miss and moves were a bit... more miss than hit really. Of course this makes it a pain in the metaphorical when I'm using a combination of SAB, Couch and Sonarr to throw files around my drives like poo in the monkey pit. I also want to make it clear that this doesn't mean Aufs is broken. The logic behind making Aufs respect underlying file permissions is simply so that data you don't want shared out with the wrong users isn't inadvertently exposed when a drive is pooled. It just means that in my context it's not super useful, especially since I'm a noob and still trying to work out the best sets of permissions/see how things interact.


    I mostly deduced all this from spending far too much quality time with WinSCP, and also looking up articles like this one: http://zackreed.me/articles/84…with-mhddfs?view=comments


    The one thing I'll miss is Aufs' speed which I've seen saturate gigabit connections. I hear Mhddfs is slower but only time will tell before I can know for sure.


    Summing it all up:
    - Changing permissions on a pooled share with Aufs doesn't seem to change the actual permissions on the disk the file is actually stored.
    - My deletes didn't always delete
    - My moves very often didn't move
    - Speed was godly


    If I weren't still trying to learn how to Linux and my data was a bit less mobile I would definitely keep using Aufs, but for now I'm going to try the other option Ryecoaaron kindly added.

    • Offizieller Beitrag
    Zitat von LostCatchphrases

    Changing permissions on a pooled share with Aufs doesn't seem to change the actual permissions on the disk the file is actually stored.


    That's been discussed several times in permission issues related threads. The most common solution is to reset permission using a "twin" share but within the branch volume.


    Somebody will have to come with a very neat script to solve this issue without doing what've I mentioned before for resetting permission. I don't use AUFS, but maybe there is a flag or option not used that can solve this problem. Did you find something like this related?

    Zitat von subzero79

    Quote from LostCatchphrases: “Changing permissions on a pooled share with Aufs doesn't seem to change the actual permissions on the disk the file is actually stored.”


    That's been discussed several times in permission issues related threads. The most…


    I did a few searches earlier and only found people's problems with Aufs seemed to be that it didn't always balance. They did mention that Aufs might be the culprit in passing but I figured if people were trying to make a decision on Mhddfs or Aufs they should probably know what issues they might run into while using it. At least if they're using it the way I did.


    I'll do another more thorough search on permissions issues now but I do like your idea. I'd have to do a lot more research into what Aufs does behind the scenes before I'm comfortable mucking about with it, but I'll keep playing with a smaller subsystem once I've gotten my housemates watching TV reliably. I'm still coming to terms with the command line, I've been coddled too much by Windows it seems!

    Oh yes!


    As far as I'm aware aufs respects pooled file permissions as a design decision. I did have a look around the man page but nothing was too forthcoming. I suspect we'll need to create a fairly robust script to chown and chmod things down a pooled directory. I can generate sort of a basic pseudocode for what needs to be done but that's about where my expertise stops. I'll look at learning bash scripting once I've gotten all of my assessments under control.

    I'm testing MergerFS that works like AUFS , but ACL and permision works as expected, see progress on: Unionfilesystem Plugin

    okay, i'll try it in the evening and tell you then


    edit: to be sure that i understand you correctly:
    I create folders on the HDDs (for example "Shared Pool" instead of "Pool"), reset all permissions. and then? Create a Pool of "Shared Pool"?


    because here: http://omv-extras.org/simple/i…d=guide-aufs-and-snapraid i read


    Zitat

    5. The drive will now show up in the Filesystems tab and is available as a drive when creating a shared folder. Do not create shared folders for the individual drives. Create a shared folder for the pool and use that in any plugin you need a shared folder for.


    ?

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