From 5dc54a39e47148803d950d2facb42500e08f4769 Mon Sep 17 00:00:00 2001 From: Laurent Bercot Date: Mon, 3 Jul 2023 18:57:42 +0000 Subject: Add s6-dns-hosts-compile, prepare for 2.3.6.0 Signed-off-by: Laurent Bercot --- doc/s6-dns-hosts-compile.html | 75 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 doc/s6-dns-hosts-compile.html (limited to 'doc/s6-dns-hosts-compile.html') diff --git a/doc/s6-dns-hosts-compile.html b/doc/s6-dns-hosts-compile.html new file mode 100644 index 0000000..c499ded --- /dev/null +++ b/doc/s6-dns-hosts-compile.html @@ -0,0 +1,75 @@ + + + + + + s6-dns: the s6-dns-hosts-compile program + + + + + + +

+s6-dns
+Software
+skarnet.org +

+ +

The s6-dns-hosts-compile program

+ +

+ s6-dns-hosts-compile compiles the system's /etc/hosts file into a +CDB file for more efficient later use by s6-dns programs that may use the +data contained in the hosts file. +

+ +

Interface

+ +

+     s6-dns-hosts-compile [ -i ifile ] [ -o ofile ]
+

+ +

s6-randomip reads the /etc/hosts file, which must follow the +traditional hosts format.
It outputs a CDB database in the /etc/hosts.cdb file.
It exits 0.

+ +

Options

+ +

-i ifile : read from ifile instead of /etc/hosts.
-o ofile : write to ofile instead of /etc/hosts.cdb.

+ +

Notes

+ +

The /etc/hosts file is an old way of specifying IP from/to domain +name correspondences. It's convenient in a pinch when a user needs to locally +override DNS data - for instance, to redirect common advertising sites to 127.0.0.1 - +but it does not map exactly to the DNS view of domain names.
Due to this, and to its line-by-line text syntax, lookups using this file +are terribly inefficient and rely on approximate qualification heuristics.
To avoid that, s6-dns tools prefer having the /etc/hosts data in +a format that's both more DNS-like and more efficient; the file output by +s6-dns-hosts-compile is the result.
When asked to take /etc/hosts data into account, s6-dns tools will +first look for a /etc/hosts.cdb file and use the data from it. If +absent, they will read the /etc/hosts file and compile its contents +into a temporary cdb file under /tmp (which they immediately unlink), +and use that cdb to query hosts data.
As a consequence, lookups are always efficient, but there's an initial +compilation step. Using s6-dns-hosts-compile to produce a /etc/hosts.cdb +file in advance saves the cost of that compilation step in subsequent +invocations of s6-dns tools.
If s6-dns tools detect that /etc/hosts has been modified more recently +than /etc/hosts.cdb, they will not use /etc/hosts.cdb and will +perform the compilation step into a temporary file. So, remember to run +s6-dns-hosts-compile after modifying your /etc/hosts.

+ + + -- cgit v1.2.3