41 lines
1.9 KiB
Markdown
41 lines
1.9 KiB
Markdown
Hostname management
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===================
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NetworkManager can update the system hostname via different
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mechanisms. The following diagram describes the workflow:
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A few notes on the diagram:
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- if there is a static hostname set in `/etc/hostname`, no action is
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taken. NetworkManager only manages the transient hostname. See the
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systemd-hostnamed
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[documentation](https://www.freedesktop.org/software/systemd/man/latest/org.freedesktop.hostname1.html#Semantics)
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about the distinction between static and transient hostname.
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- When there is no static hostname set, NetworkManager builds a
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sorted list of active devices that are eligible for the hostname
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evaluation. When doing so, the `hostname` setting of the connection
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active on each device is taken into account. Properties `from-dhcp`
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and `from-dns-lookup` determine if the two methods must be used for
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the device; property `only-from-default` determines whether devices
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without a default route should be considered, and `priority` is
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used to sort the entries. In case of a tie of the priority, a
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device with the default route comes first.
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- When evaluating a given device, first NM checks if the device
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received an hostname via DHCP and then if the first IPv4 and IPv6
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addresses configured on the interface can be resolved to a name via
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DNS. The mechanism used to perform the reverse DNS lookup of a
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specific address is described in the diagram on the right.
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- In the "spawn helper" step, NM starts a separate process that
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performs the reverse DNS lookup using the NSS services specified
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(see `man nsswitch.conf`). Service `dns` does the lookup via a DNS
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query, while `files` returns results from `/etc/hosts`.
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- In case there is no valid result from DHCP or DNS, from any device,
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if there a valid transient hostname set outside of NetworkManager,
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that hostname is honored.
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