rc(1M)rc(1M)NAMErc - general purpose sequencer invoked upon entering new run level
SYNOPSISDESCRIPTION
The shell script is the general sequencer invoked upon entering a new
run level via the command (where N equals 0-6). The script is typi‐
cally invoked by the corresponding entry in the file as follows:
is the startup and shutdown sequencer script. There is only one
sequencer script and it handles all of the sequencer directories. This
script sequences the scripts in the appropriate sequencer directories
in alphabetical order as defined by the shell and invokes them as
either startup or kill scripts.
If a transition from a lower to a higher run level (i.e., init state)
occurs, the start scripts for the new run level and all intermediate
levels between the old and new level are executed. If a transition
from a higher to a lower run level occurs, the kill scripts for the new
run level and all intermediate levels between the old and new level are
executed.
If a start script link (e.g., in sequencer N has a stop action, the
corresponding kill script should be placed in sequencer (e.g., Actions
started in level N should be stopped in level This way, a system shut‐
down (e.g., transition from level 3 directly to level 0) will result in
all subsystems being stopped.
Start and Kill Scripts
In many cases, a startup script will have both a start and a kill
action. For example, the inetd script starts the Internet daemon in
the start case, and kills that process in the stop case. Instead of
two separate scripts, only one exists, which accepts both the and argu‐
ments and executes the correct code. In some cases, only a start
action will be applicable. If this is the case, and if the action is
specified, the script should produce a usage message and exit with an
error. In general, scripts should look at their arguments and produce
error messages if bad arguments are present. When a script executes
properly, it must exit with a return value of zero. If an error condi‐
tion exists, the return value must be nonzero.
Naming Conventions
The startup and shutdown scripts (referred to as startup scripts here‐
after) exist in the directory, named after the subsystem they control.
For example, the script controls starting up the daemon. The contents
of sequencer directories consist of symbolic links to startup scripts
in These symbolic links must follow a strict naming convention, as
noted in the various fields of this example:
where the fields are defined as follows:
The sequencer directory is numbered to reflect the
run level for which its contents will be exe‐
cuted. In this case, start scripts in this
directory will be executed upon entering run
level 2 from run level 1, and kill scripts will
be executed upon entering run level 2 from run
level 3.
The first character of a sequencer link name determines
whether the script is executed as a start script
(if the character is or as a kill script (if the
character is
A three digit number is used for sequencing scripts within
the sequencer directory. Scripts are executed by
type (start or kill) in alphabetical order as
defined by the shell. Although it is not recom‐
mended, two scripts may share the same sequence
number.
The name of the startup script follows the sequence number.
The startup script name must be the same name as
the script to which this sequencer entry is
linked. In this example, the link points to
Note that short file name systems require file
names of 14 or less characters. This means that
the fourth field is limited to 10 or fewer char‐
acters.
Scripts are executed in alphabetical order. The
entire file name of the script is used for alpha‐
betical ordering purposes.
When ordering start and kill script links, note
that subsystems started in any given order should
be stopped in the reverse order to eliminate any
dependencies between subsystems. This means that
kill scripts will generally not have the same
numbers as their start script counterparts. For
example, if two subsystems must be started in a
given order due to dependencies (e.g., followed
by the kill counterparts to these scripts must be
numbered so that the subsystems are stopped in
the opposite order in which they were started
(e.g., followed by
Also keep in mind that kill scripts for a start
script in directory will reside in For example,
and might be start/kill counterparts.
Arguments
The startup/shutdown scripts should be able to recognize the following
four arguments (where applicable):
The argument is passed to scripts whose names start
with Upon receiving the argument, the script
should perform its start actions.
The argument is passed to scripts whose names start
with Upon receiving the argument, the script
should perform its stop actions.
The argument is passed to scripts whose names start
with so that the script can report back a short
message indicating what the start action will do.
For instance, when the spooler script is invoked
with a argument, it echoes
This string is used by the startup routines.
Scripts given just the argument will only print a
message and not perform any actions.
The argument is passed to scripts whose names start
with so that the script can report back a short
message indicating what the stop action will do.
For instance, when the spooler script is invoked
with a argument, it echoes
This string is used by the shutdown checklist.
Scripts given just the argument will only print a
message and not perform any actions.
Script Output
To ensure proper reporting of startup events, startup scripts are
required to comply with the following guidelines for script output.
· Status messages, such as
must be directed to stdout. All error messages must be
directed to stderr.
· Script output, both stdout and stderr, is redirected to log
file unless the startup checklist mode is set to the raw
mode. In this case, all output goes to the console. All
error messages should be echoed to stdout or stderr.
· Startup scripts are not allowed to send messages directly to
the console, or to start any daemons that immediately write
to the console. This restriction exists because these
scripts are now started by the checklist wrapper. All script
output should go to either stdout or stderr, and thus be cap‐
tured in a log file. Any console output will be garbled.
· When a startup script returns an exit code of can display a
specific message on the console prior to rebooting the sys‐
tem. This is achieved by creating a text file named contain‐
ing the text to be displayed to the console. Note that
deletes this file after displaying the message, so startup
scripts need to write this file each time a specific message
is required to be displayed on console prior to reboot.
RETURN VALUE
The return values for startup scripts are as follows:
Script exited without error.
Script encountered errors.
Script was skipped due to overriding control variables
from files, or for other reasons, and did not actually do
anything.
Script will automatically reboot the system.
Script exited without error and started a process in background
mode.
For return values greater than
the action is same as return value script encountered
errors.
SEE ALSOinit(1M), shutdown(1M), inittab(4), rc.config(4).
rc(1M)
