unidade systemd ativada não inicia na inicialização

Eu tenho um systemd-unitno meu sistema que está ativado. O problema é que ele não é reiniciado após uma reinicialização. Depende de outros dois serviços iniciados conforme o esperado.

O serviço é conhecido, ativado e desativado:

[centos@ansible-kube-4 ~]$ sudo systemctl status flanneld
flanneld.service - Flanneld overlay address etcd agent
   Loaded: loaded (/usr/lib/systemd/system/flanneld.service; enabled)
   Active: inactive (dead)

O arquivo da unidade:

[centos@ansible-kube-4 ~]$ cat /usr/lib/systemd/system/flanneld.service
[Unit]
Description=Flanneld overlay address etcd agent
After=network.target
After=etcd.service

[Service]
Type=notify
Restart=always
RestartSec=3

EnvironmentFile=/etc/sysconfig/flanneld
EnvironmentFile=-/etc/sysconfig/docker-network
ExecStart=/usr/bin/flanneld -etcd-endpoints=${FLANNEL_ETCD} -etcd-prefix=${FLANNEL_ETCD_KEY} $FLANNEL_OPTIONS
ExecStartPost=/usr/libexec/flannel/mk-docker-opts.sh -k DOCKER_NETWORK_OPTIONS -d /run/flannel/docker

[Install]
WantedBy=multi-user.target

Atualização 1

Saída de dmesg:

$ dmesg | grep systemd
[    1.312165] systemd[1]: systemd 208 running in system mode. (+PAM +LIBWRAP +AUDIT +SELINUX +IMA +SYSVINIT +LIBCRYPTSETUP +GCRYPT +ACL +XZ)
[    1.317238] systemd[1]: Detected virtualization 'kvm'.
[    1.319597] systemd[1]: Running in initial RAM disk.
[    1.323489] systemd[1]: No hostname configured.
[    1.324874] systemd[1]: Set hostname to <localhost>.
[    1.327570] systemd[1]: Initializing machine ID from KVM UUID.
[    1.389047] systemd[1]: Expecting device dev-disk-by\x2duuid-a78bb152\x2de525\x2d4f0e\x2d961a\x2dbf6147ac7d3e.device...
[    1.394577] systemd[1]: Starting -.slice.
[    1.396820] systemd[1]: Created slice -.slice.
[    1.397990] systemd[1]: Starting System Slice.
[    1.400212] systemd[1]: Created slice System Slice.
[    1.401503] systemd[1]: Starting Slices.
[    1.403556] systemd[1]: Reached target Slices.
[    1.404756] systemd[1]: Starting Timers.
[    1.406834] systemd[1]: Reached target Timers.
[    1.408042] systemd[1]: Starting Dispatch Password Requests to Console Directory Watch.
[    1.410065] systemd[1]: Started Dispatch Password Requests to Console Directory Watch.
[    1.413402] systemd[1]: Starting Paths.
[    1.415399] systemd[1]: Reached target Paths.
[    1.416574] systemd[1]: Starting Journal Socket.
[    1.418894] systemd[1]: Listening on Journal Socket.
[    1.420242] systemd[1]: Started dracut ask for additional cmdline parameters.
[    1.422150] systemd[1]: Starting dracut cmdline hook...
[    1.424870] systemd[1]: Started Load Kernel Modules.
[    1.426124] systemd[1]: Starting Journal Service...
[    1.429731] systemd[1]: Started Journal Service.
[    1.692884] systemd-udevd[213]: starting version 208
[    2.621300] systemd-journald[90]: Received SIGTERM
[    2.968711] systemd[1]: Successfully loaded SELinux policy in 274.569ms.
[    3.023076] systemd[1]: Relabelled /dev and /run in 20.031ms.
[    3.365195] systemd-udevd[382]: starting version 208
[    3.482910] systemd-journald[377]: Received request to flush runtime journal from PID 1

Atualização 2

Saída de chkconfig:

sudo chkconfig

Note: This output shows SysV services only and does not include native
      systemd services. SysV configuration data might be overridden by native
      systemd configuration.

      If you want to list systemd services use 'systemctl list-unit-files'.
      To see services enabled on particular target use
      'systemctl list-dependencies [target]'.

netconsole      0:off   1:off   2:off   3:off   4:off   5:off   6:off
network         0:off   1:off   2:on    3:on    4:on    5:on    6:off

Saída de systemctl list-dependencies flanneld:

flanneld.service
├─system.slice
└─basic.target
  ├─microcode.service
  ├─rhel-autorelabel-mark.service
  ├─rhel-autorelabel.service
  ├─rhel-configure.service
  ├─rhel-dmesg.service
  ├─rhel-loadmodules.service
  ├─paths.target
  ├─slices.target
  │ ├─-.slice
  │ └─system.slice
  ├─sockets.target
  │ ├─dbus.socket
  │ ├─rpcbind.socket
  │ ├─systemd-initctl.socket
  │ ├─systemd-journald.socket
  │ ├─systemd-shutdownd.socket
  │ ├─systemd-udevd-control.socket
  │ └─systemd-udevd-kernel.socket
  ├─sysinit.target
  │ ├─dev-hugepages.mount
  │ ├─dev-mqueue.mount
  │ ├─kmod-static-nodes.service
  │ ├─proc-sys-fs-binfmt_misc.automount
  │ ├─sys-fs-fuse-connections.mount
  │ ├─sys-kernel-config.mount
  │ ├─sys-kernel-debug.mount
  │ ├─systemd-ask-password-console.path
  │ ├─systemd-binfmt.service
  │ ├─systemd-journal-flush.service
  │ ├─systemd-journald.service
  │ ├─systemd-modules-load.service
  │ ├─systemd-random-seed.service
  │ ├─systemd-sysctl.service
  │ ├─systemd-tmpfiles-setup-dev.service
  │ ├─systemd-tmpfiles-setup.service
  │ ├─systemd-udev-trigger.service
  │ ├─systemd-udevd.service
  │ ├─systemd-update-utmp.service
  │ ├─systemd-vconsole-setup.service
  │ ├─cryptsetup.target
  │ ├─local-fs.target
  │ │ ├─-.mount
  │ │ ├─rhel-import-state.service
  │ │ ├─rhel-readonly.service
  │ │ ├─systemd-fsck-root.service
  │ │ └─systemd-remount-fs.service
  │ └─swap.target
  └─timers.target
    └─systemd-tmpfiles-clean.timer

O arquivo da unidade foi modificado:

Antes:

[Install]
RequiredBy=docker.service

Depois de:

[Install]
WantedBy=multi-user.target

Após essa modificação, não reativei a Unidade. Aconteceu que isso é necessário para o systemd reconfigurar:

$ sudo systemctl reenable flanneld
rm '/etc/systemd/system/docker.service.requires/flanneld.service'
ln -s '/usr/lib/systemd/system/flanneld.service' '/etc/systemd/system/multi-user.target.wants/flanneld.service'

Não encontro evidências em sua configuração de que esse serviço deva ser iniciado no momento da inicialização. systemdpermite duas maneiras de ativar um serviço para que ele seja iniciado no momento da inicialização:

chkconfig flanneld on

Ou:

systemctl enable flanneld

De fato, a primeira é uma maneira herdada de chamar a segunda, e não tenho certeza se o chkconfigpacote está instalado por padrão, mas você pode instalá-lo usando apt-getou yum.