This appendix covers the syntax of the gated command and the gated configuration language for Gated 3.6—the
publicly available version of gated. As
a reference to the gated configuration
language, this appendix stands on its own. But to fully understand how to
configure gated, use this reference in
conjunction with the sample configuration files in Chapter 7.
gated is constantly being
improved. As it is upgraded, the command language changes. Refer to the
latest manpages for the most recent information about gated.
The syntax of the gated command
is:
gated [-v] [-c] [-C] [-n] [-N] [-ttrace_options] [-fconfig_file] [trace_file]
The -c and -n command-line options debug the routing
configuration file without impacting the network or the kernel routing table. Frequently, these debugging options
are used with a test configuration identified by the -f config_file
option:
-cTells gated to read the
configuration file and check for syntax errors. When gated finishes reading the configuration
file, it produces a snapshot of its status and then terminates. It
writes the snapshot to /usr/tmp/gated_dump.
Running gated with the -c option does not require superuser
privileges, and it is not necessary to terminate the active
gated process.
-CChecks the configuration file for syntax errors. gated exits with a status 1 if there are
errors and 0 if there are none. Because this provides exit status,
it is useful for script files.
-nTells gated not to update
the kernel routing table. This is used to test the routing
configuration with real routing data without interfering with
system operation.
-f
config_fileTells gated to read the
configuration from config_file instead
of from the default configuration file,
/etc/gated.conf. Used in conjunction with the
-c option, -f checks a new configuration without
interfering with the currently running gated configuration.
The -v option causes gated to display its version number. When this
is used, no other options are used because gated terminates immediately after displaying
the version information.
The -N command-line option
prevents gated from running in
background mode as a daemon. This option is used when gated is started from
inittab. By default, gated runs as a daemon.
The command-line arguments
trace_options and
trace_file are used for protocol tracing. The trace_file
argument names the file to which the trace output is written. If a file
is not specified, the trace is written to the standard output. Tracing
usually produces a large amount of output.
The command-line options used for tracing are:
-tThis option turns on tracing. If -t is specified with no
trace_options, gated defaults to general tracing, which traces normal
protocol interactions and routing table changes. gated always logs protocol errors even
if no tracing is specified. You can define several different
trace_options, all of which are
described later in this appendix. A few
trace_options (detail, send, recv) cannot be specified on the
gated command line. Two others
are most useful when they are defined on the command line:
symbolsTraces the symbols read from the kernel, which is
primarily of interest to developers debugging the
interaction of gated and
the kernel.
iflistTraces the list of interfaces read from the kernel. Use this to determine what interfaces are detected by the kernel interface scan.
The advantage of placing a trace option on the command line is
that it can trace activities that happen before the configuration file
is processed. For the two options listed above, this is an essential
advantage. For other options, it is not very important. Most trace
options are specified in the configuration file. See the traceoptions command later in this appendix
for more details.
gated processes the following signals:
Tells gated to reread
the configuration file. The new configuration replaces the one
that gated is currently
running. SIGHUP loads the new configuration file without
interrupting gated service.
SIGHUP is available for quick configuration changes. At most
sites, the routing configuration changes infrequently. The few
times you need to change to a new configuration, terminate
gated and rerun it with the
new configuration. This is a more accurate test of how things
will run at the next boot.
Tells gated to snapshot
its current state to the file
/usr/tmp/gated_dump.
Tells gated to shut
down gracefully. All protocols are shut down following the rules
of that protocol. For example, EGP sends a CEASE message and
waits for it to be confirmed. SIGTERM removes from the kernel
routing table all routes learned via the exterior routing
protocols. If you need to preserve those routes while gated is out of operation, use
SIGKILL.
Tells gated to
terminate immediately and dump core. Routes are not removed from
the routing table, and no graceful shutdown is attempted.
Tells gated to toggle
tracing. If no trace flags are set, SIGUSR1 has no effect. But
if tracing is enabled, the first SIGUSR1 causes gated to toggle off tracing and to
close the trace file. The next SIGUSR1 turns tracing back on and
opens the trace file. When the trace file is closed, it can be
moved or removed without interfering with the operation of
gated. Use this to
periodically empty out the trace file to prevent it from
becoming too large.
Tells gated to check
for changes in the status of the network interfaces.
The following is an example of gated signal handling. First, the SIGUSR1
signal is passed to the gated
process using the process ID obtained from the
gated.pid file
(/var/run/gated.pid in this case).
# kill -USR1 'cat /var/run/gated.pid'Next, the old trace file
(/usr/tmp/gated.log in this case) is removed, and
gated is passed another SIGUSR1
signal.
# rm /usr/tmp/gated.log
#
kill -USR1 'cat /etc/gated.pid'After receiving the second signal, gated opens a fresh trace file (still named
/usr/tmp/gated.log). An ls shows that the new file has been
created.
# ls -l /usr/tmp/gated.log
-rw-rw-r-- 1 root 105 Jul 6 16:41 /usr/tmp/gated.log