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| author | Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> | 2022-05-17 12:25:52 +0200 |
|---|---|---|
| committer | Zbigniew Jędrzejewski-Szmek <zbyszek@in.waw.pl> | 2022-05-17 12:50:09 +0200 |
| commit | 45b1321653ba0e508f20eaf2c31772e5b206c0d8 (patch) | |
| tree | ae689d1e28145bdbcdfdbedbfec6e4ce62312b33 /docs/NETWORK_ONLINE.md | |
| parent | 3b098432be44cd1fd64bf1cf9a945ebcc39a1ec7 (diff) | |
| download | systemd-45b1321653ba0e508f20eaf2c31772e5b206c0d8.tar.gz | |
docs: say how to delay network-online.target
Could be related to https://access.redhat.com/solutions/4879291.
Unfortunately I can't access this page, but the title seems
relevant.
Diffstat (limited to 'docs/NETWORK_ONLINE.md')
| -rw-r--r-- | docs/NETWORK_ONLINE.md | 35 |
1 files changed, 35 insertions, 0 deletions
diff --git a/docs/NETWORK_ONLINE.md b/docs/NETWORK_ONLINE.md index 7317d7ef8b..1a81bf4ca4 100644 --- a/docs/NETWORK_ONLINE.md +++ b/docs/NETWORK_ONLINE.md @@ -224,3 +224,38 @@ it does not delay boot. It is usually easier to write such a service in a be (re-)established, but is instead started when the network has connectivity, and if the network goes away, it fails and relies on the system manager to restart it if appropriate. + +## Modyfing the meaning of `network-online.target` + +As described above, the meaning of this target is defined first by which +implementing services are enabled (`NetworkManager-wait-online.service`, +`systemd-networkd-wait-online.service`, …), and second by the configuration +specific to those services. + +For example, `systemd-networkd-wait-online.service` will wait until all +interfaces that are present and managed by +[systemd-networkd.service(8)](http://www.freedesktop.org/software/systemd/man/systemd-networkd.service.html). +are fully configured or failed and at least one link is online; see +[systemd-networkd-wait-online.service(8)](http://www.freedesktop.org/software/systemd/man/systemd-networkd-wait-online.service.html) +for details. Those conditions are affected by the presence of configuration +that matches various links, but also by settings like +`Unmanaged=`, `RequiredForOnline=`, `RequiredFamilyForOnline=`; see +[systemd.network(5)](http://www.freedesktop.org/software/systemd/man/systemd.socket.html). + +It is also possible to plug in additional checks for network state. For +example, to delay `network-online.target` until some a specific host is +reachable (the name can be resolved over DNS and the appropriate route has been +established), the following simple service could be used: + +```ini +[Unit] +DefaultDependencies=no +After=nss-lookup.target +Before=network-online.target + +[Service] +ExecStart=sh -c 'while ! ping -c 1 example.com; do sleep 1; done' + +[Install] +WantedBy=network-online.target +``` |