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| -rw-r--r-- | examples/var_service/README | 18 |
1 files changed, 13 insertions, 5 deletions
diff --git a/examples/var_service/README b/examples/var_service/README index 52dd781ef..41106b5ae 100644 --- a/examples/var_service/README +++ b/examples/var_service/README @@ -40,8 +40,8 @@ There are just two key programs in runit. Firstly, runsv supervises the process for an individual service. Service directories themselves sit inside a containing directory, and the runsvdir program supervises that directory, running one child runsv process for the service in each -subdirectory. Out of the box on Debian, for example, an instance of -runsvdir supervises services in subdirectories of /var/service/. +subdirectory. A typical choice is to start an instance of runsvdir +which supervises services in subdirectories of /var/service/. If /var/service/log/ exists, runsv will supervise two services, and will connect stdout of main service to the stdin of log service. @@ -94,7 +94,7 @@ dhcp, zeroconf, ppp, openvpn and such. They need to be controlled, and in many cases you also want to babysit them. They present a case where different services need to control (start, stop, -restart) eact other. +restart) each other. var_service/dhcp_if @@ -110,7 +110,9 @@ dynamic network link services (ppp/vpn/zcip). This is an example of service with has a "finish" script. If downed ("sv d"), "finish" is executed. For this service, it removes DHCP address from -the interface. +the interface. This is useful when ifplugd detects that the the link is dead +(cable is no longer attached anywhere) and downs us - keeping DHCP configured +addresses on the interface would make kernel still try to use it. var_service/zcip_if @@ -138,6 +140,9 @@ inteface "if". var_service/fw +"Firewall" script, although it is tasked with much more than setting up firewall. +It is responsible for all aspects of network configuration. + This is an example of *one-shot* service. It reconfigures network based on current known state of ALL interfaces. @@ -147,7 +152,7 @@ Uses conf/*.ipconf (static config) and /var/run/service/fw/*.ipconf One-shot-ness of this service means that it shuts itself off after single run. IOW: it is not a constantly running daemon sort of thing. It starts, it configures the network, it shuts down, all done -(unlike infamous NetworkManagers which sit in RAM forever, doing hell knows what). +(unlike infamous NetworkManagers which sit in RAM forever). However, any dhcp/ppp/vpn or similar service can restart it anytime when it senses the change in network configuration. @@ -158,10 +163,13 @@ This is achieved very simply by having # Make ourself one-shot sv o . at the very beginning of fw/run script, not at the end. + Therefore, any "sv u /var/run/service/fw" command by any other script "undoes" o(ne-shot) command if fw still runs, thus runsv will rerun it; or start it in a normal way if fw is not running. +This mechanism is the reason why fw is a service, not just a script. + System administrators are expected to edit fw/run script, since network configuration needs are likely to be very complex and different for non-trivial installations. |