Solaris Service Management Facility - Quickstart Guide

Introduction

UNIX operating systems have traditionally included a set of services: software programs not associated with any interactive user login that listen for and respond to requests to perform certain tasks, such as delivering email, responding to ftp requests, or permitting remote command execution. These traditional services were usually individual applications that executed as a single process that started at boot time and executed continuously while a system was up and running, servicing any requests that were received.

Today, administrators must contend with a collection of services that has grown to such a point that it has exceeded the utility of this original model. Sun has created the Service Management Facility (SMF) to simplify management of these system services. SMF is a new feature of the Solaris Operating System that creates a supported, unified model for services and service management on each Solaris system. It is a core part of the Predictive Self-Healing technology available in Solaris 10, which provides automatic recovery from software and hardware failures as well as administrative errors.

In this guide, we'll describe the features and benefits of SMF, point out some parts of Solaris that have changed significantly, and show how to accomplish typical administration tasks using SMF. A comprehensive guide to SMF and Predictive Self-Healing is available on Sun's BigAdmin website.

The following figure shows the primary components of the SMF framework. When you boot an image, SMF updates the service configuration repository if necessary, reads the repository data, and starts service instances that are enabled. In the following figure, libscf is the library interface that the restarters use to interact with the service configuration repository. Interaction between the service configuration repository and libscf library interfaces is managed by the svc.configd daemon. The svcs, svcprop, svcadm, and svccfg commands are the interface that administrators use to interact with the service configuration repository.

Open

Features

The Service Management Facility has improved several aspects of the Solaris administrative model. Some of the most notable updates are:

• Services are represented as first-class objects that can be viewed (using the new svcs(1) command) and managed (using svcadm(1M) and svccfg(1M)).

• Failed services are automatically restarted in dependency order, whether they failed as the result of administrator error, software bug, or were affected by an uncorrectable hardware error.

• More information is available about misconfigured or misbehaving services, including an explanation of why a service isn't running (using "svcs -x"), as well as individual, persistent log files for each service.

• Problems during the boot process are easier to debug, as boot verbosity can be controlled, service startup messages are logged, and console access is provided more reliably during startup failures.

• Snapshots of service configurations are taken automatically, making it easier to backup, restore, and undo changes to services.

• Services can be enabled and disabled using a supported tool (svcadm(1M)), allowing the changes to persist across upgrades and patches.

• Administrators can securely delegate tasks to non-root users more easily, including the ability to configure, start, stop, or restart services (as described in the smf_security(5) man page).

• Large systems boot faster by starting services in parallel according to their dependencies.

Despite these changes, compatibility with existing administrative practices has been preserved wherever possible. For example, most site-local and ISV-supplied "rc" scripts will still work as usual.

Notable Changes

Most of the new features provided by SMF happen "behind the scenes" or are accessed by new commands; however, some changes will be apparent very quickly. Here's what some of these changes look like.

In previous versions of Solaris, a fair amount of output would be printed to the system console during boot. Although the messages gave some insight into what was happening, they were not very helpful in several regards. A handful of services would print messages indicating that they had come on line, while many others didn't. Some failure modes would print messages (such as "WARNING: Timed out waiting for NIS to come up") that didn't help diagnose the underlying problem. Error messages would sometimes be printed directly to the console, but they wouldn't show up in any log.

The boot process is much quieter now. Here's an example of what a machine looks like while booting under SMF:

Although fewer messages are printed, SMF has made the boot process more observable. Each service has a log file in the /var/svc/log directory (or the /etc/svc/volatile directory, for services started before the single-user milestone) indicating when and how it was started, whether it started successfully, and any messages it may have printed during its initialization. If a severe problem occurs during boot, you will be able to log in on the console in maintenance mode, and you can use the svcs(1) command to help diagnose the problem. This is even the case for problems which would have caused boot to hang -- such as the NIS failure mentioned above. Finally, the new "-m" boot option (see kernel(1M)) allows you to configure the boot process to be more verbose, printing a simple message when each service starts.

You may also notice processes "refusing to die" after being killed. For example:

At first glance, it may appear that nothing happened, despite having used kill -9. But notice that the PIDs are different, and the process start times have changed; the old sendmail processes did, in fact, die.

SMF has added the notion of the relationship between a service, its processes, and another service that is responsible for restarting the service, to the Solaris kernel. This restart relationship is tightly integrated with Sun's new technologies for fault management on Solaris, permitting SMF restarters to understand whether a service process failed as the result of an administrator error, failure of a dependent service, software bug, or underlying hardware failure. Once this information has been captured following any service failure, SMF informs the appropriate restarter, which decides either to disable the service by placing it in maintenance mode because it appears to be defective, or to restart it automatically. The default SMF restarter, svc.startd, is responsible for starting and restarting most of the services on your Solaris system. In the example above, svc.startd noticed that sendmail had died, logged a message to that effect, and restarted it automatically.

If you want to stop a service and not have its processes restarted, use the svcadm(1M) command (see the "Common Tasks" section below). Note also that not all system services have been converted to use SMF yet; any processes belonging to these legacy services will not be restarted if they are killed.

Finally, you may notice that the /etc/init.d and /etc/rc*.d directories, as well as the /etc/inittab file, are quite a bit emptier than in previous releases of Solaris. SMF-managed services no longer use rc scripts or inittab entries for startup and shutdown, so the scripts corresponding to those services have been removed. In future releases of Solaris, more services will be managed by SMF, and these directories will become less and less populated. rc scripts and inittab entries which manage ISV-provided or locally developed services will continue to be run at boot. These services may not run at exactly the same point in boot as they had before the advent of SMF, but they are guaranteed to not run any earlier -- so any services which they had implicitly depended on will still be available.

Service Names

Solaris uses a URI string called an FMRI (Fault Managed Resource Identifier) to identify system objects for which advanced fault and resource management capabilities are provided. Services managed by SMF are assigned FMRI strings prefixed with the scheme name "svc", as shown in the following examples for the Solaris service syslogd(1M):

• svc://localhost/system/system-log:default

• svc:/system/system-log:default

• system/system-log:default

Notice that these service FMRIs used by SMF can be expressed in three ways: first as an absolute path including a location path such as "localhost"; second as a path relative to the local machine; and third as simply the service identifier with the string prefixes implied. The SMF administrator tools described in the rest of this document typically describe services using the third form, as they are assumed to be operating on local services. Other management tools that operate on multiple types of resources or across machine boundaries may use one of the other forms to describe services. The SMF tools in the current release of Solaris can only manage services on the local host.

Since the FMRI strings are fairly long, the SMF tools allow abbreviated forms of the FMRIs to be used. The abbreviation must be unique, must match the trailing part of the service name (although the ":default" can be left off), and it must begin after a "/". So the following are acceptable abbreviations of the above FMRI:

• system-log:default

• system-log

These abbreviations should be used with care, as a new service may be added at some point that includes the same substring (e.g. "svc:/mysite/system-log:default"). The SMF tools will print a warning if a non-unique abbreviation is used.

The FMRIs for Solaris system services include a general functional category, such as "application", "milestone", "network", "platform", and "system", as well as a descriptive name similar to the name of the service's daemon or the old rc script. The svcs(1) command will list all active services available on a machine:

Since services are now first-class objects, SMF can even provide information about services that aren't enabled, using the "-a" option of the svcs(1) command.

Common Tasks

SMF is a particularly notable change in Solaris because it impacts the administrative model. So although we encourage you to read more about the features of SMF (see the "More information" section below), you may want to start by learning how to do some common system administration tasks.

• Enabling and disabling services

  Prior to Solaris 10, there wasn't a good way to permanently disable a service in Solaris. The typical method used is to rename the relevant rc script to a name that won't get executed, but that change will get overlooked the next time the system is upgraded. Furthermore, inetd-based services are enabled and disabled by a totally different method -- editing a configuration file. Under SMF, both types of services can be configured using the svcadm(1M) command, and the changes will persist if the machine is upgraded. Here's a comparison of how to enable and disable some services:

The last argument to svcadm in these examples is the FMRI of the service.

Note that svcadm should only be used for SMF services -- legacy rc script-controlled services work the same as in past releases.

• Stopping, starting, and restarting services

  Traditionally, services have been started by an rc script run at boot, run with the argument start. Some rc scripts provide a stop option, and a few also allow restart. In SMF, these tasks are all accomplished with the svcadm(1M) command:

The "-t" option to svcadm enable and svcadm disable indicates that the requested action should be temporary -- it will not affect whether the service is started the next time that the system boots. This is in contrast to the "Enabling and disabling services" example, above.

As with the enabling and disabling of services, svcadm should not be used to control rc script-controlled services; they continue to work the same as in past releases.

• Observing the boot process

  As mentioned in the "Notable Changes" section, the boot process is much quieter by default than in previous releases of Solaris. This was done to reduce the amount of uninformative "chatter" that might obscure any real problems that might occur during boot.

  Some new boot options have been added to control the verbosity of boot. One that you may find particularly useful is "-m verbose", which prints a line of information when each service attempts to start up. This is similar to the default boot mode for some other UNIX-based and UNIX-like operating systems. Verbose boot looks like this:

  The order of the service start messages may change from boot to boot, because SMF starts services in parallel according to their dependency relationships.

  If a service fails to start successfully, warning messages will be printed in addition to the start message. Here's an example where the NTP service failed to start up:

  The first two error messages would appear during both normal boot and verbose boot; the last one ("network/ntp:default misconfigured ...") would only appear during verbose boot.

• Discovering what's going wrong

  Solaris has not had a comprehensive place to look for problems with system services. Some solutions exist to help catch and diagnose these problems, ranging from coreadm(1M) logging to site-specific monitoring scripts to comprehensive products such as Sun Cluster. The new svcs(1) command includes an "explain" option ("svcs -x"), which prints out detailed, solution-driven messages about the services that are not running. svcs -x shows when and why the service failed, provides pointers to more information about the problem, and lists what other services are affected by this problem.

  Continuing with the example of the NTP service failing to start up:

  The NTP service has been placed into maintenance mode because the startup script indicated that there was a problem with the service's configuration. Further information about the service failure is available in the service's log file in the /var/svc/log directory (or the /etc/svc/volatile directory). The log file name is based off the short form of the FMRI, with "/"'s replaced by "-"'s. So the log file for the svc:/network/ntp:default service is /var/svc/log/network-ntp:default.log. This log file quickly led to the conclusion that the NTP daemon's configuration file, /etc/inet/ntp.conf, had been removed.

  Another example shows SMF's ability to track dependencies and point out problems relating to disabled services. We use the "-v" option in this example to see the list of impacted services.

  Here, the application/print/server:default service has been explicitly disabled, but another service which depended on it (application/print/rfc1179:default) was not disabled. So the disabling of the first service has kept the second one from running.

• Observing services

  In earlier versions of Solaris, the only way to see what services were available was to use the ps(1) command and list all the active processes on the system, and then look around for the names of processes that match the names of service applications. Unfortunately, since most systems have many processes, and new services are introduced with each new version of Solaris and when other software packages are added, it's very difficult to track things this way. To further complicate the situation, many modern services are no longer implemented as single processes. Some services are implemented as collections of processes, multi-threaded processes, or both simultaneously.

  The new svcs(1) command makes it much easier to observe the status of a system service. The "-p" option shows all the processes associated with a service:

  The "-d" option shows what other services this service depends on, and the "-D" option shows what other services depend on this service:

  We can see that sendmail requires networking, local file systems, name services, the syslog daemon, and the automount daemon to be running before it will run, and sendmail itself must be running before the multi-user milestone can be reached. The service start times (the STIME column) illustrate that these dependencies have been followed.

• Changing run levels

  SMF has introduced the concept of milestones, which supplant the traditional notion of run levels. Run levels provide a basic description of the set of services running on the machine, traditionally grouped as the services necessary for one user to log in on the machine console (run level S), and for multiple users to log in to the machine (run levels 2 and 3). These system states are represented in SMF as milestones, which are stable services that represent a group of other services. "svcs -d" can be used to see what services must be running before a milestone is reached.

  svcadm(1M) is now the preferred method of setting the system's default run level. This is done with the milestone subcommand and the FMRI of a valid milestone:

The "-d" option indicates that the default milestone should be set to the named FMRI. Without "-d", "svcadm milestone" transitions the system to the named milestone immediately.

The boot process has been updated to be aware of milestones. In addition to the traditional "boot -s" (boot into single-user mode), there is now "boot -m milestone=<milestone>", to boot to the named milestone. <milestone> can be "single-user", "multi-user", or "multi-user-server", as well as the special milestones "all" (all enabled services online) and "none" (no services at all). The "none" milestone can be very useful in repairing systems that have failures early in the boot process.

Booting to the single-user milestone (with "-m milestone=single-user") is slightly different than the old "boot -s". When the system is explicitly booted to a milestone, exiting the console administrative shell will not transition the system to multi-user mode, as "boot -s" does. To move to multi-user mode after "boot -m milestone=single-user", use the command "svcadm milestone milestone/multi-user-server:default".

• Enabling, disabling, and monitoring legacy services

  Services that are started by traditional rc scripts (referred to as legacy services) will generally continue to work as they always have. They will show up in the output of svcs(1), with an FMRI based on the pathname of their rc script, but they can not be controlled by svcadm(1M). They should be stopped and started by running the rc script directly.

  As mentioned in the "Notable Changes" section, rc scripts may not run at exactly the same point in boot as they had in earlier versions of Solaris. In particular, scripts which depend on running before certain Solaris-provided rc scripts may encounter problems. The vast majority of scripts should continue to work without any trouble, though.

• Adding new services to inetd.conf

  The Internet services daemon, inetd(1M), has been rewritten as part of SMF. It stores all of its configuration data in the SMF database, rather than /etc/inet/inetd.conf, allowing the SMF tools to be used to control and observe inetd-based services. Most inetd-based services that ship with Solaris will no longer have entries in inetd.conf. To provide compatibility for services which haven't converted to SMF, entries can still be added to inetd.conf using the same syntax as always, and the new inetconv(1M) command will convert the new services to SMF services. inetconv should always be run after editing /etc/inet/inetd.conf; it can be run without any arguments.