Several most often used options have corresponding environment
variables. If given the --env option, genrc will
consult them, if the corresponding option was not supplied.
Don’t forget to export these environment variables before invoking
genrc.
The list of environment variables and corresponding command line options follows:
| Variable | Option |
|---|---|
GENRC_COMMAND=command | --command=command |
GENRC_CREATE_PIDFILE=name | --create-pidfile=name |
GENRC_GROUP=groups | --group=groups |
GENRC_KILL_MODE=mode | --kill-mode=mode |
GENRC_LOG_ERR_FILE=file | --log-err-file=file |
GENRC_LOG_FACILITY=name | --log-facility=name |
GENRC_LOG_FILE=file | --log-file=file |
GENRC_LOG_OUT_FILE=file | --log-out-file=file |
GENRC_LOG_TAG=str | --log-tag=str |
GENRC_PID_FROM=source | --pid-from=source |
GENRC_PROGRAM=name | --program=name |
GENRC_SENTINEL=1 | --sentinel |
GENRC_SIGNAL_RELOAD=sig | --signal-reload=sig |
GENRC_SIGNAL_STOP=sig | --signal-stop=sig |
GENRC_TIMEOUT=seconds | --timeout=seconds |
GENRC_USER=name | --user=name |
It was supposed that the use of environment options might improve readability of startup scripts. For instance, the example script from the first chapter can be rewritten as follows:
#! /bin/sh PIDFILE=/var/run/ntpd.pid export GENRC_COMMAND="/usr/sbin/ntpd -g -p $PIDFILE" export GENRC_PID_FROM="FILE:$PIDFILE" exec /sbin/genrc --env --no-reload --signal-stop=SIGHUP "$@"
However, it was soon found out that relying on the environment can
also lead to some hard-to-diagnose failures. Suppose, for example,
that you set GENRC_USER=nobody to experiment with some
program. When done, you forget to unset it and restart
ntpd, using the script above. As a result, ntpd
will start with the privileges of user ‘nobody’ and fail,
consequently.
The use of the explicit option --env is supposed to diminish
probability of such failures. When used without arguments, the option
instructs genrc to consult all variables from the list
above, if their corresponding options are not given. You can also
further restrict the use of environment to a subset of that list. For
example, the above script can further be modified as
#! /bin/sh
PIDFILE=/var/run/ntpd.pid
export GENRC_COMMAND="/usr/sbin/ntpd -g -p $PIDFILE"
export GENRC_PID_FROM="FILE:$PIDFILE"
exec /sbin/genrc --env=GENRC_COMMAND,GENRC_PID_FROM \
--no-reload --signal-stop=SIGHUP "$@"
This way, genrc will use only the two variables explicitly
set in the script.
Up to version 1.5.3, environment variables were used by default.
Obviously, existing scripts should be changed upon upgrading to
version 2.0. To help catch the cases when people fail to do so,
genrc issues a warning, if it detects that some of the
above variables are set and the --env option is not
supplied. For example (long lines being split for readability):
genrc: warning: the following environment variables are set,
but not used:
genrc: GENRC_COMMAND
genrc: GENRC_SENTINEL
genrc: warning: use --env to use these variables, or --no-env to
suppress this warning
The normal course of action when encountering such warning is to
modify the script in question by either supplying the --env
to genrc, so that it makes use of the environment, or by
removing environment settings and using corresponding options instead.
The warning proposes also the third way: if, for some reason, you want to retain environment settings without actually using them, use the --no-env option to indicate that you are aware of the situation and its possible implications.