[systemd-devel] Ensuring that a unit starts before any networking

[Dave Howorth]

On Sat, 27 Jun 2020 11:42:00 +0100
Mark Rogers <mark at more-solutions.co.uk> wrote:
> On Sat, 27 Jun 2020 at 11:06, Zbigniew Jędrzejewski-Szmek
> <zbyszek at in.waw.pl> wrote:
> > You should use Before=network-pre.target,
> > Wants=network-pre.target.  
> 
> Thanks, tried that but still not working:
> 
> $ journalctl -b | grep -Ei '(db2config|dhcpcd)'
> Feb 14 10:12:03 localhost systemd[1]: Starting dhcpcd on all
> interfaces... Feb 14 10:12:03 localhost dhcpcd[341]: read_config:
> fopen `/etc/dhcpcd.conf': No such file or directory
> [...]
> Jun 27 10:19:39 localhost dhcpcd[341]: wlan0: /etc/wpa_supplicant.conf
> does not exist
> [...]
> Jun 27 10:19:39 localhost dhcpcd[341]: read_config: fopen
> `/etc/dhcpcd.conf': No such file or directory
> [...]
> Jun 27 10:19:40 localhost dhcpcd[341]: eth0: soliciting an IPv6 router
> Jun 27 10:19:40 localhost dhcpcd[341]: eth0: soliciting a DHCP lease
> Jun 27 10:19:41 mypi db2config.py[325]: 2020-06-27 10:19:41 db2config
> Creating /tmp/sys//etc/dhcpcd.conf
> Jun 27 10:19:41 mypi db2config.py[325]: 2020-06-27 10:19:41 db2config
> Creating /tmp/sys//etc/wpa_supplicant/wpa_supplicant.conf
> 
> (Comments about that extract: the jump from Feb to Jun I assume is the
> clock getting updated from RTC, it's all from the same boot obviously;

A Pi doesn't normally have an RTC, so the mixup usually takes place
when the time is updated via NTP I believe. Do you have an RTC?

> also note my db2config script doesn't run until after hostname is set
> which I would assume is set by the network startup?)

Well that depends how you've set the Pi up, so you tell us, don't
assume. If your script doesn't start until hostname is set and hostname
is set by dhcp then you have a fundamental problem.

> Unit file is currently:
> 
> [Unit]
> Description=Config generation from DB
> Before=network-pre.target
> Wants=network-pre.target
> 
> [Service]
> Type=oneshot
> ExecStart=/home/mark/bin/db2config.py
> 
> [Install]
> RequiredBy=network.target
> 
> After any changes I'm using
> $ sudo systemctl daemon-reload
> $ sudo systemctl reenable db2config.service
> 
> ... although that's another area I'm not entirely clear about what
> exactly is required after a unit file change.
> 
> PS: Is list etiquette around here to CC on reply? Some love it, some
> hate it, others don't care...
> 
> 
> --
> Mark Rogers
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