[Bug 1636912] Re: systemd-networkd runs too late for cloud-init.service (net)

[Martin Pitt]

> I did play with it, but the networkd in xenial blocks for some non-trivial
> amount of time (10s of seconds) if dbus.service is not up. 

I cannot reproduce this. I removed /etc/network/interface*, created

$ cat /etc/systemd/network/ens3.network 
[Match]
Name=e*

[Network]
DHCP=yes

then dropped the After=dbus.service from systemd-networkd.service and
enabled it. Booting and bringing up the ethernet is fast. Even with
"systemctl mask dbus.service" it is fast, just that logind and thermald
fail to start (expectedly). So how did you get this hang?

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Title:
  systemd-networkd runs too late for cloud-init.service (net)

Status in systemd:
  New
Status in cloud-init package in Ubuntu:
  Triaged
Status in systemd package in Ubuntu:
  Triaged
Status in cloud-init source package in Xenial:
  New
Status in systemd source package in Xenial:
  Triaged

Bug description:
  Ubuntu Core 16 images using cloud-init fail to function when the
  DataSource is over the network (Like OpenStack) as networking is not
  yet available when cloud-init.service runs.

  cloud-init service unit deps look like this:

  [Unit]
  Description=Initial cloud-init job (metadata service crawler)
  DefaultDependencies=no
  Wants=cloud-init-local.service
  Wants=local-fs.target
  Wants=sshd-keygen.service
  Wants=sshd.service
  After=cloud-init-local.service
  After=networking.service
  Requires=networking.service
  Before=basic.target
  Before=dbus.socket
  Before=network-online.target
  Before=sshd-keygen.service
  Before=sshd.service
  Before=systemd-user-sessions.service
  Conflicts=shutdown.target

  Here's networkd unit deps:

  [Unit]
  Description=Network Service
  Documentation=man:systemd-networkd.service(8)
  ConditionCapability=CAP_NET_ADMIN
  DefaultDependencies=no
  # dbus.service can be dropped once on kdbus, and systemd-udevd.service can be
  # dropped once tuntap is moved to netlink
  After=systemd-udevd.service dbus.service network-pre.target systemd-sysusers.service systemd-sysctl.service
  Before=network.target multi-user.target shutdown.target
  Conflicts=shutdown.target
  Wants=network.target

  # On kdbus systems we pull in the busname explicitly, because it
  # carries policy that allows the daemon to acquire its name.
  Wants=org.freedesktop.network1.busname
  After=org.freedesktop.network1.busname

  
  And a critical-chain output:

  root at snap-test7:~# systemd-analyze critical-chain systemd-networkd
  Failed to get ID: Unit name systemd-networkd is not valid.
  The time after the unit is active or started is printed after the "@" character.
  The time the unit takes to start is printed after the "+" character.

  root at snap-test7:~# systemd-analyze critical-chain systemd-networkd.service
  The time after the unit is active or started is printed after the "@" character.
  The time the unit takes to start is printed after the "+" character.

  systemd-networkd.service +440ms
  └─dbus.service @11.461s
    └─basic.target @11.403s
      └─sockets.target @11.401s
        └─dbus.socket @11.398s
          └─cloud-init.service @10.127s +1.266s
            └─networking.service @9.305s +799ms
              └─network-pre.target @9.295s
                └─cloud-init-local.service @3.822s +5.469s
                  └─local-fs.target @3.813s
                    └─run-cgmanager-fs.mount @12.687s
                      └─local-fs-pre.target @1.393s
                        └─systemd-tmpfiles-setup-dev.service @1.116s +195ms
                          └─kmod-static-nodes.service @887ms +193ms
                            └─system.slice @783ms
                              └─-.slice @721ms

  
  cloud-init would need networkd to run at or before 'networking.service' so it can raise networking to then find and use network-based datasources.

  # grep systemd /usr/share/snappy/dpkg.list 
  ii  libnss-resolve:amd64          229-4ubuntu11                                            amd64        nss module to resolve names via systemd-resolved
  ii  libpam-systemd:amd64          229-4ubuntu11                                            amd64        system and service manager - PAM module
  ii  libsystemd0:amd64             229-4ubuntu11                                            amd64        systemd utility library
  ii  systemd                       229-4ubuntu11                                            amd64        system and service manager
  ii  systemd-sysv                  229-4ubuntu11                                            amd64        system and service manager - SysV links

  # grep cloud-init /usr/share/snappy/dpkg.list 
  ii  cloud-init                    0.7.8-201610260005-gf7a5756-0ubuntu1~trunk~ubuntu16.04.1 all          Init scripts for cloud instances

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