ipsec auto [ --show ] [ --showonly ] operation
The --add operation adds a connection specification to the internal database within pluto; it will fail if pluto already has a specification by that name. The --delete operation deletes a connection specification from pluto's internal database (also tearing down any connections based on it); it will fail if the specification does not exist. The --replace operation is equivalent to --delete (if there is already a specification by the given name) followed by --add, and is a convenience for updating pluto's internal specification to match an external one. (Note that a --rereadsecrets may also be needed.) None of the other operations alters the internal database.
The --up operation asks pluto to establish a connection based on an entry in its internal database. The --down operation tells pluto to tear down such a connection.
Normally, pluto establishes a route to the destination specified for a connection as part of the --up operation. However, the route and only the route can be established with the --route operation. Until and unless an actual connection is established, this discards any packets sent there, which may be preferable to having them sent elsewhere based on a more general route (e.g., a default route).
Normally, pluto's route to a destination remains in place when a --down operation is used to take the connection down (or if connection setup, or later automatic rekeying, fails). This permits establishing a new connection (perhaps using a different specification; the route is altered as necessary) without having a ``window'' in which packets might go elsewhere based on a more general route. Such a route can be removed using the --unroute operation (and is implicitly removed by --delete).
The --ready operation tells pluto to listen for connection-setup requests from other hosts. Doing an --up operation before doing --ready on both ends is futile and will not work, although this is now automated as part of IPsec startup and should not normally be an issue.
The --status operation asks pluto for current connection status. The output format is ad-hoc and likely to change.
The --rereadsecrets operation tells pluto to re-read the /etc/ipsec.secrets secret-keys file, which it normally reads only at startup time. (This is currently a synonym for --ready, but that may change.)
The --show option turns on the -x option of the shell used to execute the commands, so each command is shown as it is executed.
The --showonly option causes auto to show the commands it would run, on standard output, and not run them.
The --asynchronous option, applicable only to the up operation, tells pluto to attempt to establish the connection, but does not delay to report results. This is especially useful to start multiple connections in parallel when network links are slow.
The --verbose option instructs auto to pass through all output from ipsec_whack(8), including log output that is normally filtered out as uninteresting.
The --config option specifies a non-standard location for the IPsec configuration file (default /etc/ipsec.conf).
See ipsec.conf(5) for details of the configuration file. Apart from the basic parameters which specify the endpoints and routing of a connection (left and right, plus possibly leftsubnet, leftnexthop, leftfirewall, their right equivalents, and perhaps type), an auto connection almost certainly needs a keyingtries parameter (since the keyingtries default is poorly chosen).
There is no support for passthrough connections.
A connection description which uses %defaultroute for one of its nexthop parameters but not the other may be falsely rejected as erroneous in some circumstances.
The exit status of --showonly does not always reflect errors discovered during processing of the request. (This is fine for human inspection, but not so good for use in scripts.)