Switch to ifnames persistent network names

We do have stable interface names, through the exact same way (/lib/udev/rules.d/75-persistent-net-generator.rules) as we've had for many years. I proposed to switch to ifnames a few days ago (https://lists.ubuntu.com/archives/ubuntu-devel/2015-May/038761.html), if you want you can already try that by deleting /etc/udev/rules.d/70-persistent-net.rules and booting with "net.ifnames=1".

Which package /etc/udev/rules.d/70-persistent-net.rules belongs to? I'd like to make sure that it won't reappear after I update something.

It's created dynamically, please see the referenced email. You can remove that file and add net.ifnames=1 to the kernel command line to use the new-style naming.

Just to double-check the net.ifnames=1 is ubuntu-specific quirk. Will anything break if I'll boot to mainline kernel?
What generates this 70-... file and when? I'd like to make sure it's not generated again after upgrade. Predictability of network interfaces (and correspondingly firewall rules etc) is of paramount importance for remote installations.

Ok, re-tested with mainline - works fine.

No, this isn't kernel specific. net.ifnames is evaluated by udev.

This bug was fixed in the package systemd - 220-6ubuntu2

---------------
systemd (220-6ubuntu2) wily; urgency=medium

  * Merge with Debian packaging git head. Remaining Ubuntu changes:
    - Hack to support system-image read-only /etc, and modify files in
      /etc/writable/ instead.
    - Keep our much simpler udev maintainer scripts (all platforms must
      support udev, no debconf).
    - initramfs init-top: Drop scsi_wait_scan and udevadm settle, we do that
      in a more sensible way with wait-for-root.
    - initramfs init-bottom: If LVM is installed, settle udev,
      otherwise we get missing LV symlinks. Workaround for LP #1185394.
    - Add debian/udev.lvm2.init: Dummy SysV init script to satisfy insserv
      dependencies to "lvm2" which is handled with udev rules in Ubuntu.
    - Add debian/udev.lvm2.service to avoid running the dummy lvm2 init
      script.
    - Provide shutdown fallback for upstart. (LP: #1370329)
    - debian/extra/ifup@.service: Additionally run for "auto" class. We don't
      really support "allow-hotplug" in Ubuntu at the moment, so we need to
      deal with "auto" devices appearing after "/etc/init.d/networking start"
      already ran. (LP: #1374521) Also run ifup in the background during boot,
      to avoid blocking network.target. (LP: #1425376)
    - ifup@.service: Drop dependency on networking.service (i. e.
      /etc/init.d/networking), and merely ensure that /run/network exists.
      This avoids unnecessary dependencies/waiting during boot and dependency
      cycles if hooks wait for other interfaces to come up (like ifenslave
      with bonding interfaces). (LP: #1414544)
    - Add Get-RTC-is-in-local-time-setting-from-etc-default-rc.patch: In
      Ubuntu we currently keep the setting whether the RTC is in local or UTC
      time in /etc/default/rcS "UTC=yes|no", instead of /etc/adjtime.
      (LP: #1377258)
    - Put session scopes into all cgroup controllers. This makes unprivileged
      user LXC containers work under systemd. (LP: #1346734)
    - systemctl: Don't forward telinit u to upstart. This works around
      upstart's Restart() always reexec'ing /sbin/init on Restart(), even if
      that changes to point to systemd during the upgrade. This avoids running
      systemd during a dist-upgrade. (LP: #1430479)
    - Drop hwdb-update dependency from udev-trigger.service, which got
      introduced in v219-stable. This causes udev and plymouth to start too
      late and isn't really needed in Ubuntu yet as we don't support stateless
      systems yet and handle hwdb.bin updates through dpkg triggers. This can
      be dropped again with initramfs-tools 0.117.
    - Lower Breaks: to plymouth version which has the udev inotify fix in
      Ubuntu.
    - Lower apparmor Breaks: to the Ubuntu version that dropped $remote_fs.
    - Change systemd-sysv's conflicts to upstart-sysv. (LP: #1422681)

    Upgrade fixes, keep until 16.04 LTS release:
    - systemd Conflicts/Replaces/Provides systemd-services.
    - Remove obsolete systemd-logind upstart job.
    - Clean up obsolete /etc/udev/rules.d/README.

systemd (220-7) UNRELEASED; urgency=medium

  [ Michael Biebl ]
  * Enable seccomp su...