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https://github.com/docker-mailserver/docker-mailserver.git
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63 lines
2.9 KiB
Bash
63 lines
2.9 KiB
Bash
#! /bin/bash
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# Outputs the DNS label count (delimited by `.`) for the given input string.
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# Useful for determining an FQDN like `mail.example.com` (3), vs `example.com` (2).
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function _get_label_count
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{
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awk -F '.' '{ print NF }' <<< "${1}"
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}
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# Sets HOSTNAME and DOMAINNAME globals used throughout the scripts,
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# and any subprocesses called that intereact with it.
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function _obtain_hostname_and_domainname
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{
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# Normally this value would match the output of `hostname` which mirrors `/proc/sys/kernel/hostname`,
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# However for legacy reasons, the system ENV `HOSTNAME` was replaced here with `hostname -f` instead.
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#
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# TODO: Consider changing to `DMS_FQDN`; a more accurate name, and removing the `export`, assuming no
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# subprocess like postconf would be called that would need access to the same value via `$HOSTNAME` ENV.
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#
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# TODO: `OVERRIDE_HOSTNAME` was introduced for non-Docker runtimes that could not configure an explicit hostname.
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# k8s was the particular runtime in 2017. This does not update `/etc/hosts` or other locations, thus risking
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# inconsistency with expected behaviour. Investigate if it's safe to remove support. (--net=host also uses this as a workaround)
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export HOSTNAME="${OVERRIDE_HOSTNAME:-$(hostname -f)}"
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# If the container is misconfigured.. `hostname -f` (which derives it's return value from `/etc/hosts` or DNS query),
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# will result in an error that returns an empty value. This warrants a panic.
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if [[ -z ${HOSTNAME} ]]
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then
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dms_panic__misconfigured 'obtain_hostname' '/etc/hosts'
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fi
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# If the `HOSTNAME` is more than 2 labels long (eg: mail.example.com),
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# We take the FQDN from it, minus the 1st label (aka _short hostname_, `hostname -s`).
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#
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# TODO: For some reason we're explicitly separating out a domain name from our FQDN,
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# `hostname -d` was probably not the correct command for this intention either.
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# Needs further investigation for relevance, and if `/etc/hosts` is important for consumers
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# of this variable or if a more deterministic approach with `cut` should be relied on.
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if [[ $(_get_label_count "${HOSTNAME}") -gt 2 ]]
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then
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if [[ -n ${OVERRIDE_HOSTNAME} ]]
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then
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# Emulates the intended behaviour of `hostname -d`:
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# Assign the HOSTNAME value minus everything up to and including the first `.`
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DOMAINNAME=${HOSTNAME#*.}
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else
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# Operates on the FQDN returned from querying `/etc/hosts` or fallback DNS:
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#
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# Note if you want the actual NIS `domainname`, use the `domainname` command,
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# or `cat /proc/sys/kernel/domainname`.
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# Our usage of `domainname` is under consideration as legacy, and not advised
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# going forward. In future our docs should drop any mention of it.
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#shellcheck disable=SC2034
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DOMAINNAME="$(hostname -d)"
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fi
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fi
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# Otherwise we assign the same value (eg: example.com):
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# Not an else statement in the previous conditional in the event that `hostname -d` fails.
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DOMAINNAME="${DOMAINNAME:-${HOSTNAME}}"
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}
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