SMF_METHOD(5)SMF_METHOD(5)NAMEsmf_method - service management framework conventions for methods
DESCRIPTION
The class of services managed by svc.startd(1M) in the service manage‐
ment framework, smf(5), consists of applications that fit a simple
fork(2)-exec(2) model. The svc.startd(1M) master daemon and other
restarters support the fork(2)-exec(2) model, potentially with addi‐
tional capabilities. The svc.startd(1M) daemon and other restarters
require that the methods which activate, manipulate, or examine a ser‐
vice instance follow the conventions described in this manual page.
Invocation form
The form of a method invocation is not dictated by convention. In some
cases, a method invocation might consist of the direct invocation of
the daemon or other binary executable that provides the service. For
cases in which an executable script or other mediating executable is
used, the convention recommends the form:
/path/to/method_executable abbr_method_name
The abbr_method_name used for the recommended form is a supported
method such as start or stop. The set of methods supported by a
restarter is given on the related restarter page. The svc.startd(1M)
daemon supports start, stop, and refresh methods.
A restarter might define other kinds of methods beyond those referenced
in this page. The conventions surrounding such extensions are defined
by the restarter and might not be identical to those given here.
Environment Variables
The restarter provides four environment variables to the method that
determine the context in which the method is invoked.
SMF_FMRI
The service fault management resource identifier (FMRI) of the
instance for which the method is invoked.
SMF_METHOD
The full name of the method being invoked, such as start or stop.
SMF_RESTARTER
The service FMRI of the restarter that invokes the method
SMF_ZONENAME
The name of the zone in which the method is running. This can also
be obtained by using the zonename(1) command.
These variables should be removed from the environment prior to the
invocation of any persistent process by the method. A convenience shell
function, smf_clear_env, is given for service authors who use Bourne-
compatible shell scripting to compose service methods in the include
file described below.
The method context can cause other environment variables to be set as
described below.
Method Definition
A method is defined minimally by three properties in a propertygroup of
type method.
These properties are:
exec (astring)
Method executable string.
timeout_seconds (count)
Number of seconds before method times out.
See the Timeouts section for more detail.
type (astring)
Method type. Currently always set to method.
A Method Context can be defined to further refine the execution envi‐
ronment of the method. See the Method Context section for more informa‐
tion.
Method Tokens
When defined in the exec string of the method by the restarter
svc.startd, a set of tokens are parsed and expanded with appropriate
value. Other restarters might not support method tokens. The delegated
restarter for inet services, inetd(1M), does not support the following
method expansions.
%%
%
%r
Name of the restarter, such as svc.startd
%m
The full name of the method being invoked, such as start or stop.
%s
Name of the service
%i
Name of the instance
%f
FMRI of the instance
%{prop[:,]}
Value(s) of a property. The prop might be a property FMRI, a prop‐
erty group name and a property name separated by a /, or a property
name in the application property group. These values can be fol‐
lowed by a , (comma) or : (colon). If present, the separators are
used to separate multiple values. If absent, a space is used. The
following shell metacharacters encountered in string values are
quoted with a (backslash):
; & ( ) | ^ < > newline space tab " '
An invalid expansion constitutes method failure.
Two explicit tokens can be used in the place of method commands.
:kill [-signal]
Sends the specified signal, which is SIGTERM by default, to all
processes in the primary instance contract. Always returns
SMF_EXIT_OK. This token should be used to replace common pkill
invocations.
:true
Always returns SMF_EXIT_OK. This token should be used for methods
that are required by the restarter but which are unnecessary for
the particular service implementation.
Exiting and Exit Status
The required behavior of a start method is to delay exiting until the
service instance is ready to answer requests or is otherwise func‐
tional.
The following exit status codes are defined in <libscf.h> and in the
shell support file.
SMF_EXIT_OK 0 Method exited, per‐
forming its opera‐
tion successfully.
SMF_EXIT_ERR_FATAL 95 Method failed
fatally and is
unrecoverable with‐
out administrative
intervention.
SMF_EXIT_ERR_CONFIG 96 Unrecoverable con‐
figuration error. A
common condition
that returns this
exit status is the
absence of required
configuration files
for an enabled ser‐
vice instance.
SMF_EXIT_ERR_NOSMF 99 Method has been
mistakenly invoked
outside the smf(5)
facility. Services
that depend on
smf(5) capabilities
should exit with
this status value.
SMF_EXIT_ERR_PERM 100 Method requires a
form of permission
such as file
access, privilege,
authorization, or
other credential
that is not avail‐
able when invoked.
SMF_EXIT_ERR_OTHER non-zero Any non-zero exit
status from a
method is treated
as an unknown
error. A series of
unknown errors can
be diagnosed as a
fault by the
restarter or on
behalf of the
restarter.
Use of a precise exit code allows the responsible restarter to catego‐
rize an error response as likely to be intermittent and worth pursuing
restart or permanent and request administrative intervention.
Timeouts
Each method can have an independent timeout, given in seconds. The
choice of a particular timeout should be based on site expectations for
detecting a method failure due to non-responsiveness. Sites with repli‐
cated filesystems or other failover resources can elect to lengthen
method timeouts from the default. Sites with no remote resources can
elect to shorten the timeouts. Method timeout is specified by the time‐
out_seconds property.
If you specify 0 timeout_seconds for a method, it declares to the
restarter that there is no timeout for the service. This setting is not
preferred, but is available for services that absolutely require it.
-1 timeout_seconds is also accepted, but is a deprecated specification.
Shell Programming Support
A set of environment variables that define the above exit status values
is provided with convenience shell functions in the file
/lib/svc/share/smf_include.sh. This file is a Bourne shell script suit‐
able for inclusion via the source operator in any Bourne-compatible
shell.
To assist in the composition of scripts that can serve as SMF methods
as well as /etc/init.d scripts, the smf_present() shell function is
provided. If the smf(5) facility is not available, smf_present()
returns a non-zero exit status.
One possible structure for such a script follows:
if smf_present; then
# Shell code to run application as managed service
....
smf_clear_env
else
# Shell code to run application as /etc/init.d script
....
fi
This example shows the use of both convenience functions that are pro‐
vided.
Method Context
The service management facility offers a common mechanism set the con‐
text in which the fork(2)-exec(2) model services execute.
The desired method context should be provided by the service developer.
All service instances should run with the lowest level of privileges
possible to limit potential security compromises.
A method context can contain the following properties:
use_profile
A boolean that specifies whether the profile should be used instead
of the user, group, privileges, and limit_privileges properties.
environment
Environment variables to insert into the environment of the method,
in the form of a number of NAME=value strings.
profile
The name of an RBAC (role-based access control) profile which,
along with the method executable, identifies an entry in
exec_attr(4).
user
The user ID in numeric or text form.
group
The group ID in numeric or text form.
supp_groups
An optional string that specifies the supplemental group member‐
ships by ID, in numeric or text form.
privileges
An optional string specifying the privilege set as defined in priv‐
ileges(5).
limit_privileges
An optional string specifying the limit privilege set as defined in
privileges(5).
working_directory
The home directory from which to launch the method. :home can be
used as a token to indicate the home directory of the user whose
uid is used to launch the method. If the property is unset, :home
is used.
corefile_pattern
An optional string that specifies the corefile pattern to use for
the service, as per coreadm(1M). Most restarters supply a default.
Setting this property overrides local customizations to the global
core pattern.
project
The project ID in numeric or text form. :default can be used as a
token to indicate a project identified by getdefaultproj(3PROJECT)
for the user whose uid is used to launch the method.
resource_pool
The resource pool name on which to launch the method. :default can
be used as a token to indicate the pool specified in the project(4)
entry given in the project attribute above.
The method context can be set for the entire service instance by speci‐
fying a method_context property group for the service or instance. A
method might override the instance method context by providing the
method context properties on the method property group.
Invalid method context settings always lead to failure of the method,
with the exception of invalid environment variables that issue warn‐
ings.
In addition to the context defined above, many fork(2)-exec(2) model
restarters also use the following conventions when invoking executables
as methods:
Argument array
The arguments in argv[] are set consistently with the result
/bin/sh -c of the exec string.
File descriptors
File descriptor 0 is /dev/null. File descriptors 1 and 2 are recom‐
mended to be a per-service log file.
FILES
/lib/svc/share/smf_include.sh
Definitions of exit status values.
/usr/include/libscf.h
Definitions of exit status codes.
SEE ALSOzonename(1), coreadm(1M), inetd(1M), svccfg(1M), svc.startd(1M),
exec(2), fork(2), getdefaultproj(3PROJECT), exec_attr(4), project(4),
service_bundle(4), attributes(5), privileges(5), rbac(5), smf(5),
smf_bootstrap(5), zones(5)NOTES
The present version of smf(5) does not support multiple repositories.
When a service is configured to be started as root but with privileges
different from limit_privileges, the resulting process is privilege
aware. This can be surprising to developers who expect seteuid(<non-
zero UID>) to reduce privileges to basic or less.
May 20, 2009 SMF_METHOD(5)
