On Tue, Sep 1, 2015 at 9:20 PM, Erming Pei <erm...@ualberta.ca> wrote: > Hi, > > I tried to set up a read-only permission for a client but it looks always > writable. > > I did the following: > > ==Server end== > > [client.cephfs_data_ro] > key = AQxxxxxxxxxx== > caps mon = "allow r" > caps osd = "allow r pool=cephfs_data, allow r pool=cephfs_metadata"
The clients don't directly access the metadata pool at all so you don't need to grant that. :) And I presume you have an MDS cap in there as well? > > > ==Client end== > mount -v -t ceph hostname.domainname:6789:/ /cephfs -o > name=cephfs_data_ro,secret=AQxxxxxxxxxx== > > But I still can touch, delete, overwrite. > > I read that touch/delete could be only meta data operations, but why I still > can overwrite? > > Is there anyway I could test/check the data pool (instead of meta data) to > see if any effect on it? What you're seeing here is an unfortunate artifact of the page cache and the way these user capabilities work in Ceph. As you surmise, touch/delete are metadata operations through the MDS and in current code you can't block the client off from that (although we have work in progress to improve things). I think you'll find that the data you've overwritten isn't really written to the OSDs — you wrote it in the local page cache, but the OSDs will reject the writes with EPERM. I don't remember the kernel's exact behavior here though — we updated the userspace client to preemptively check access permissions on new pools but I don't think the kernel ever got that. Zheng? -Greg _______________________________________________ ceph-users mailing list ceph-users@lists.ceph.com http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
