Am Thu, 2 Nov 2017 22:59:36 -0400 schrieb Dave <davestechs...@gmail.com>:
> On Thu, Nov 2, 2017 at 7:07 AM, Austin S. Hemmelgarn > <ahferro...@gmail.com> wrote: > > On 2017-11-01 21:39, Dave wrote: > >> I'm going to make this change now. What would be a good way to > >> implement this so that the change applies to the $HOME/.cache of > >> each user? > >> > >> The simple way would be to create a new subvolume for each existing > >> user and mount it at $HOME/.cache in /etc/fstab, hard coding that > >> mount location for each user. I don't mind doing that as there are > >> only 4 users to consider. One minor concern is that it adds an > >> unexpected step to the process of creating a new user. Is there a > >> better way? > >> > > The easiest option is to just make sure nobody is logged in and run > > the following shell script fragment: > > > > for dir in /home/* ; do > > rm -rf $dir/.cache > > btrfs subvolume create $dir/.cache > > done > > > > And then add something to the user creation scripts to create that > > subvolume. This approach won't pollute /etc/fstab, will still > > exclude the directory from snapshots, and doesn't require any > > hugely creative work to integrate with user creation and deletion. > > > > In general, the contents of the .cache directory are just that, > > cached data. Provided nobody is actively accessing it, it's > > perfectly safe to just nuke the entire directory... > > I like this suggestion. Thank you. I had intended to mount the .cache > subvolumes with the NODATACOW option. However, with this approach, I > won't be explicitly mounting the .cache subvolumes. Is it possible to > use "chattr +C $dir/.cache" in that loop even though it is a > subvolume? And, is setting the .cache directory to NODATACOW the right > choice given this scenario? From earlier comments, I believe it is, > but I want to be sure I understood correctly. It is important to apply "chattr +C" to the _empty_ directory, because even if used recursively, it won't apply to already existing, non-empty files. But the +C attribute is inherited by newly created files and directory: So simply follow the "chattr +C on empty directory" and you're all set. BTW: You cannot mount subvolumes from an already mounted btrfs device with different mount options. That is currently not implemented (except for maybe a very few options). So the fstab approach probably wouldn't have helped you (depending on your partition layout). You can simply just create subvolumes within the location needed and they are implicitly mounted. Then change the particular subvolume cow behavior with chattr. -- Regards, Kai Replies to list-only preferred. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
