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16d489851e
nit-picking PR, when using the name of the plugin make it cursive. Signed-off-by: Miek Gieben <miek@miek.nl>
126 lines
4.0 KiB
Markdown
126 lines
4.0 KiB
Markdown
# hosts
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## Name
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*hosts* - enables serving zone data from a `/etc/hosts` style file.
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## Description
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The *hosts* plugin is useful for serving zones from a `/etc/hosts` file. It serves from a preloaded
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file that exists on disk. It checks the file for changes and updates the zones accordingly. This
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plugin only supports A, AAAA, and PTR records. The hosts plugin can be used with readily
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available hosts files that block access to advertising servers.
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The plugin reloads the content of the hosts file every 5 seconds. Upon reload, CoreDNS will use the
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new definitions. Should the file be deleted, any inlined content will continue to be served. When
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the file is restored, it will then again be used.
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If you want to pass the request to the rest of the plugin chain if there is no match in the *hosts*
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plugin, you must specify the `fallthrough` option.
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This plugin can only be used once per Server Block.
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## The hosts file
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Commonly the entries are of the form `IP_address canonical_hostname [aliases...]` as explained by
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the hosts(5) man page.
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Examples:
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~~~
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# The following lines are desirable for IPv4 capable hosts
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127.0.0.1 localhost
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192.168.1.10 example.com example
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# The following lines are desirable for IPv6 capable hosts
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::1 localhost ip6-localhost ip6-loopback
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fdfc:a744:27b5:3b0e::1 example.com example
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~~~
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### PTR records
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PTR records for reverse lookups are generated automatically by CoreDNS (based on the hosts file
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entries) and cannot be created manually.
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## Syntax
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~~~
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hosts [FILE [ZONES...]] {
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[INLINE]
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ttl SECONDS
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no_reverse
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reload DURATION
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fallthrough [ZONES...]
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}
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~~~
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* **FILE** the hosts file to read and parse. If the path is relative the path from the *root*
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plugin will be prepended to it. Defaults to /etc/hosts if omitted. We scan the file for changes
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every 5 seconds.
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* **ZONES** zones it should be authoritative for. If empty, the zones from the configuration block
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are used.
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* **INLINE** the hosts file contents inlined in Corefile. If there are any lines before fallthrough
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then all of them will be treated as the additional content for hosts file. The specified hosts
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file path will still be read but entries will be overridden.
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* `ttl` change the DNS TTL of the records generated (forward and reverse). The default is 3600 seconds (1 hour).
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* `reload` change the period between each hostsfile reload. A time of zero seconds disables the
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feature. Examples of valid durations: "300ms", "1.5h" or "2h45m". See Go's
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[time](https://godoc.org/time). package.
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* `no_reverse` disable the automatic generation of the `in-addr.arpa` or `ip6.arpa` entries for the hosts
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* `fallthrough` If zone matches and no record can be generated, pass request to the next plugin.
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If **[ZONES...]** is omitted, then fallthrough happens for all zones for which the plugin
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is authoritative. If specific zones are listed (for example `in-addr.arpa` and `ip6.arpa`), then only
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queries for those zones will be subject to fallthrough.
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## Metrics
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If monitoring is enabled (via the *prometheus* plugin) then the following metrics are exported:
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- `coredns_hosts_entries{}` - The combined number of entries in hosts and Corefile.
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- `coredns_hosts_reload_timestamp_seconds{}` - The timestamp of the last reload of hosts file.
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## Examples
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Load `/etc/hosts` file.
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~~~ corefile
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. {
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hosts
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}
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~~~
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Load `example.hosts` file in the current directory.
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~~~
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. {
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hosts example.hosts
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}
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~~~
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Load example.hosts file and only serve example.org and example.net from it and fall through to the
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next plugin if query doesn't match.
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~~~
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. {
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hosts example.hosts example.org example.net {
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fallthrough
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}
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}
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~~~
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Load hosts file inlined in Corefile.
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~~~
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example.hosts example.org {
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hosts {
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10.0.0.1 example.org
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fallthrough
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}
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whoami
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}
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~~~
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## See also
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The form of the entries in the `/etc/hosts` file are based on IETF [RFC 952](https://tools.ietf.org/html/rfc952) which was updated by IETF [RFC 1123](https://tools.ietf.org/html/rfc1123).
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