aufs doesn't support file capabilities

[geofft]

$ getcap /usr/bin/timidity 
Failed to get capabilities of file `/usr/bin/timidity' (Operation not supported)
$ getcap /bin/ls
Failed to get capabilities of file `/bin/ls' (Operation not supported)

petards, hosting, etc. etc.

[geofft]

Not sure if it's aufs or tmpfs (but likely both). A patch to add file capability support to tmpfs was just posted to LKML:

 http://lwn.net/Articles/422624/

If Ubuntu starts relying more on file capabilities, like Fedora is (which was the motivation for this patch), and if we start pushing #761, then we'll actually need to care.

[geofft]

So AUFS finally implemented support for xattrs and therefore for file capabilities in March 2015:  https://github.com/sfjro/aufs4-standalone/commit/6660bf6 , behind the CONFIG_AUFS_XATTR config option, which is off by default. (This support should be in the versions of AUFS for kernel 4.0 and up, if I'm reading this right.)

The CONFIG_AUFS_XATTR option was enabled in Ubuntu 15.10 with kernel 4.2.0-38.45, Ubuntu 16.04 with kernel 4.4.0-22.39, and Ubuntu 16.10 with kernel 4.8.0-30.32. It looks like it's not supported at all in older versions of Ubuntu, certainly not in 14.04. See  https://pad.lv/1557776

The CONFIG_AUFS_XATTR option is not currently enabled in Debian. The kernel in Debian 8 "Jessie" (current stable), 3.16, is too old anyway. In Debian 9 "Stretch" (current testing), AUFS is in a separate package called aufs-dkms, but the option is disabled. I've filed  https://bugs.debian.org/863166 requesting that it be enabled, although it's likely too late for the Stretch release.

Debathena only uses AUFS on Ubuntu, right? Then this ticket can probably be closed.