Isso resolveu o problema.
Aberto em /etc/init.d/networking e definido CONFIGURE_INTERFACES=no
Eu tentei a Solução aqui sem sucesso, usando sudo systemctl edit networking.service e adicionando TimeoutStartSec = 10seg. Mas sudo systemd-analyze blame ainda coloca networking.service em mais de 5 minutos. Eu verifiquei a mudança após a inicialização e o arquivo networking.service ainda tem o tempo limite. Posso me livrar de networking.service completamente desde que eu usei ifup ?
sudo systemctl status networking.service dá:
● networking.service - Raise network interfaces
Loaded: loaded (/lib/systemd/system/networking.service; enabled; vendor preset: enabled)
Drop-In: /etc/systemd/system/networking.service.d
└─override.conf
Active: failed (Result: timeout) since Tue 2017-07-18 19:16:48 MDT; 30min ago
Docs: man:interfaces(5)
Main PID: 912 (code=killed, signal=TERM)
Jul 18 19:16:48 musty systemd[1]: networking.service: Start operation timed out. Terminating.
Jul 18 19:16:48 musty systemd[1]: networking.service: Main process exited, code=killed, status=15/TERM
Jul 18 19:16:48 musty systemd[1]: Failed to start Raise network interfaces.
Jul 18 19:16:48 musty systemd[1]: networking.service: Unit entered failed state.
Jul 18 19:16:48 musty systemd[1]: networking.service: Failed with result 'timeout'.
Jul 18 19:16:59 musty systemd[1]: [/etc/systemd/system/networking.service.d/override.conf:1] Assignment
Jul 18 19:17:51 musty systemd[1]: [/etc/systemd/system/networking.service.d/override.conf:1] Assignment
Jul 18 19:28:11 musty systemd[1]: [/etc/systemd/system/networking.service.d/override.conf:1] Assignment
Jul 18 19:29:08 musty systemd[1]: [/etc/systemd/system/networking.service.d/override.conf:1] Assignment
Jul 18 19:35:57 musty systemd[1]: [/etc/systemd/system/networking.service.d/override.conf:1] Assignment
Isso resolveu o problema.
Aberto em /etc/init.d/networking e definido CONFIGURE_INTERFACES=no