SMF_METHOD(5) Standards, Environments, and Macros SMF_METHOD(5)


NAME


smf_method - service management framework conventions for methods

DESCRIPTION


The class of services managed by svc.startd(1M) in the service management
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 additional
capabilities. The svc.startd(1M) daemon and other restarters require that
the methods which activate, manipulate, or examine a service 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
environment of the method. See the Method Context section for more
information.

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 property
group name and a property name separated by a /, or a property name
in the application property group. These values can be followed 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 functional.


The following exit status codes are defined in <libscf.h> and in the
shell support file.


SMF_EXIT_OK 0 Method exited,
performing its
operation
successfully.
SMF_EXIT_NODAEMON 94 Method exited
successfully but
purposefully leaves
no processes
remaining in the
contract; it should
be treated as if it
had a transient
service model.
SMF_EXIT_ERR_FATAL 95 Method failed
fatally and is
unrecoverable
without
administrative
intervention.
SMF_EXIT_ERR_CONFIG 96 Unrecoverable
configuration error.
A common condition
that returns this
exit status is the
absence of required
configuration files
for an enabled
service 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
available 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 categorize
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
replicated 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
timeout_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
suitable 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
provided.

Method Context


The service management facility offers a common mechanism set the context
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 memberships
by ID, in numeric or text form.


privileges

An optional string specifying the privilege set as defined in
privileges(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.


security_flags

The security flags to apply when launching the method. See security-
flags(5).


The "default" keyword specifies those flags specified in
svc:/system/process-security. The "all" keyword enables all flags,
the "none" keyword enables no flags. The "current" keyword specifies
the current flags. Flags may be added by specifying their name
(optionally preceded by '+'), and removed by preceding their name
with '-').


Use of "all" has associated risks, as future versions of the system
may include further flags which may harm poorly implemented software.


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
specifying 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 warnings.


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
recommended 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 ALSO


zonename(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), security-flags(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.


February 25, 2019 SMF_METHOD(5)