Enabling and disabling services

| Stephen | Product.

I thought I would show a different example of smf(5) today. Here’s the state of the network/telnet service on my desktop:







  svcs -p network/telnet:default







  STATE          STIME    FMRI
  online         Jul_23   svc:/network/telnet:default

It’s easy to enable and disable service instances using svcadm(1M):




  svcadm disable network/telnet




  svcs -p network/telnet:default




  STATE          STIME    FMRI
  disabled       13:08:15 svc:/network/telnet:default




  telnet localhost




  Trying 127.0.0.1...
  telnet: Unable to connect to remote host: Connection refused

And we can enable it just as easily, too:




  svcadm enable network/telnet




  svcs -p network/telnet:default




  STATE          STIME    FMRI
  online         13:08:29 svc:/network/telnet:default

Note that while something is declaring telnet service is available, no processes are associated with the service instance. If we “telnet localhost” from another window, we can then see the telnet daemon and the login session:




  svcs -p network/telnet:default




  STATE          STIME    FMRI
  online         13:08:52 svc:/network/telnet:default
  13:08:52   116400 in.telnetd
  13:08:52   116403 login

Support for enabling and disabling services can be done by calling smf_enable_instance(3SCF) and smf_disable_instance(3SCF), in addition to the command line interface of svcadm(1M). Since the framework relays the enable or disable request, we don’t need privileges to signal any process (or even know which process we might have to signal to make the update…).