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--- docs:guide-developer:procd-init-scripts [2019/09/02 17:47] – [Examples] link added tmomas
+++ docs:guide-developer:procd-init-scripts [2024/02/10 16:23] (current) – [Defining service instances] systemcrash
@@ Line 1: / Line 1: @@
-======procd init script parameters ======
+====== procd init scripts ======
 A procd init script is similiar to an old init script, but with a few differences:
-  * procd expects services to **run in the foreground**
+  * procd expects services to start as if they were to  **run in the foreground**, but of course procd runs them the background.
   * Different shebang line: ''#!/bin/sh /etc/rc.common''
+  * procd expects that shell variable (not environment variable) ''initscript'' is set to the path of the script that invoked it
   * Explicitly use procd ''USE_PROCD=1''
 Example:
-<code>
+<code bash>
 #!/bin/sh /etc/rc.common
@@ Line 14: / Line 15: @@
 </code>
-To start a service we need the function 'start_service'. stop_service is only needed when you need special things to stop your service. stop_service() is called //after// procd killed the service.
+===== How do these scripts work? =====
-The service itself **should** run in the **foreground**. (Apparently
-<code>
+Init script has to handle two main tasks:
+  - Define current configuration (state) for service instance(s)
+  - Specify when (and optionally how) to reconfigure service
+Defining configuration is handled in the ''start_service()''. For each instance to be run it has to specify service command and all its parameters. All that info is stored internally by ''procd''. On a single change (compared to the last used configuration) ''procd'' restarts a service.
+Init script has to specify all possible ''procd'' events that may require service reconfiguration. Defining all triggers is done in the ''service_triggers()'' using ''procd_add_*_trigger'' helpers.
+Optionally init script may handle service reconfiguration process on its own. It's useful for services that don't require complete restart to use new configuration. It can be handled by specifying custom ''reload_service()'' which prevents ''start_service()'' from being called and so stops ''procd'' from restarting service.
+===== Defining service instances =====
+The purpose of ''start_service()'' (see next section to see when it's called) is to define instance(s) with:
+  - Command to execute to start service
+  - Information on what to observe for changes (e.g. files or devices) - optional
+  - Settings that ''procd'' should use (e.g. auto respawning, logging stdout, user to use) - optional
+The above information is stored by ''procd'' as a service instance state. On every relevant system change (e.g. config change), ''start_service()'' is called by designed triggers. If it generates any different state (e.g. command will change) than the previous one, ''procd'' will detect it and restart the service.
+Defining service instance details is handled by setting parameters. Some values are set directly in the ''start_service()'' (like ''command'') while some are determined by ''procd'' (like ''file'' and file hash). There are two helpers for setting parameters:
+  - ''procd_set_param()''
+  - ''procd_append_param()''
+The below example lists supported parameters and describes them. For implementation details see the [[commit>?p=openwrt/openwrt.git;a=blob;f=package/system/procd/files/procd.sh|procd.sh]].
+<code bash>
 start_service() {
-  procd_open_instance [instance_name]
+         procd_open_instance [instance_name]
-  procd_set_param command /sbin/your_service_daemon -b -a --foo
+         procd_set_param command /sbin/your_service_daemon -b -a --foo # service executable that has to run in **foreground**.
-  procd_append_param command -bar 42 # append command parameters
+         procd_append_param command -bar 42 # append command parameters
-  # respawn automatically if something died, be careful if you have an alternative process supervisor
+         # respawn automatically if something died, be careful if you have an alternative process supervisor
-  # if process dies sooner than respawn_threshold, it is considered crashed and after 5 retries the service is stopped
+         # if process exits sooner than respawn_threshold, it is considered crashed and after 5 retries the service is stopped
-  procd_set_param respawn ${respawn_threshold:-3600} ${respawn_timeout:-5} ${respawn_retry:-5}
+         # if process finishes later than respawn_threshold, it is restarted unconditionally, regardless of error code
+         # notice that this is literal respawning of the process, not in a respawn-on-failure sense
+         procd_set_param respawn ${respawn_threshold:-3600} ${respawn_timeout:-5} ${respawn_retry:-5}
-  procd_set_param env SOME_VARIABLE=funtimes  # pass environment variables to your process
+         procd_set_param env SOME_VARIABLE=funtimes  # pass environment variables to your process
-  procd_set_param limits core="unlimited"  # If you need to set ulimit for your process
+         procd_set_param limits core="unlimited"  # If you need to set ulimit for your process
-  procd_set_param file /var/etc/your_service.conf # /etc/init.d/your_service reload will restart the daemon if these files have changed
+         procd_set_param file /var/etc/your_service.conf # /etc/init.d/your_service reload will restart the daemon when these files have changed
-  procd_set_param netdev dev # likewise, except if dev's ifindex changes.
+         procd_set_param netdev dev # likewise, but for when dev's ifindex changes.
-  procd_set_param data name=value ... # likewise, except if this data changes.
+         procd_set_param data name=value ... # likewise, but for when this data changes.
-  procd_set_param stdout 1 # forward stdout of the command to logd
+         procd_set_param stdout 1 # forward stdout of the command to logd
-  procd_set_param stderr 1 # same for stderr
+         procd_set_param stderr 1 # same for stderr
-  procd_set_param user nobody # run service as user nobody
+         procd_set_param user nobody # run service as user nobody
-  procd_set_param pidfile /var/run/somefile.pid # write a pid file on instance start and remove it on stop
+         procd_set_param pidfile /var/run/somefile.pid # write a pid file on instance start and remove it on stop
-  procd_close_instance
+         procd_set_param term_timeout 60 # wait before sending SIGKILL
+         procd_close_instance
 }
 </code>
-{{:meta:icons:tango:48px-dialog-warning.svg.png?32}}WARNING{{:meta:icons:tango:48px-dialog-warning.svg.png?32}}: initscripts **will run** while building OpenWRT images (when installing packages in what will become a ROM image) in the **host system** (right now, for actions "//enable//" and "//disable//").  **They must not fail, or have undesired side-effects in that situation.**  When being run by the build system, environment variable **${IPKG_INSTROOT}** will be set to the working directory being used.  On the "target system", that environment variable will be empty/unset.  Refer to "/lib/functions.sh" and also to "/etc/rc.common" in package "base-files" for the nasty details.
+==== Stopping services ====
-TODO: Table old openwrt initscript <-> new procd
+''stop_service()'' is only needed when you need special things to stop your service. ''stop_service()'' is called //before// procd killed the service.
-FIXME For as much information as is available, see the documentation at the top of [[https://git.openwrt.org/?p=openwrt/svn-archive/archive.git;a=blob;f=package/system/procd/files/procd.sh;h=1c2edc67994d37513d1a244bba1bc882217758c0;hb=HEAD|procd.sh]] //("See the source" is not documentation.)//
+If you want to add a check //after// procd has sent the terminate signal (e.g. wait for the process to be really gone), you can define an extra function ''service_stopped()''.
-===== Procd triggers on config file / network interface changes =====
+==== Init scripts during compilation ====
-In older versions of OpenWrt, a system called "ucitrack" attempted to track UCI config files, and the processes that depended on each of them, and would restart them all as needed.  This too, is replaced with ubus/procd, and expanded to allow notifying services when network interfaces change.  This is useful for services like dnsmasq, and proxy/routing software that cares about which network interfaces are in use, and with what configuration.
+{{:meta:icons:tango:48px-dialog-warning.svg.png?32}}WARNING{{:meta:icons:tango:48px-dialog-warning.svg.png?32}}: initscripts **will run** while building OpenWrt images (when installing packages in what will become a ROM image) in the **host system** (right now, for actions "//enable//" and "//disable//").  **They must not fail, or have undesired side-effects in that situation.**  When being run by the build system, environment variable **${IPKG_INSTROOT}** will be set to the working directory being used.  On the "target system", that environment variable will be empty/unset.  Refer to "/lib/functions.sh" and also to "/etc/rc.common" in package "base-files" for the nasty details.
-First, to simply make your service depend on a config file, add a "service_triggers()" clause to your init script
+===== Specifying triggers =====
-<code>
+While ''start_service()'' takes care of setting service instances states and submitting them to the ''procd'' (for a potential service restart), it has to be explicitly called to do so. In most cases it should happen on some related change.
+That's where ''service_triggers()'' comes in handy and allows specifying triggers. Most system important changes result in generating events that ''service_triggers()'' can use for triggering various actions. There are multiple ''procd_add_*_trigger()'' helpers for that purpose.
+Every configurable service has to specify what system changes should result in its reconfiguration. Those events should be defined in the ''service_triggers()'' using available helpers. When related ''procd'' ''service'' event occurs it will result in executing ''/etc/init.d/<foo> reload''.
+Example:
+<code bash>
 service_triggers()
 {
-        procd_add_reload_trigger "uci-file-name"
+        procd_add_reload_trigger "<uci-file-name>" "<second-uci-file>"
+        procd_add_reload_interface_trigger <interface>
+        procd_add_reload_mount_trigger <path> [<path> ...]
 }
 </code>
-This will setup hooks such that issuing '''reload_config''' will issue a call to '''/etc/init.d/<yourinitscript> reload''' when the md5sums of '''/etc/config/uci-file-name''' has changed.
+^ Function                           ^ Arguments            ^ Event used        ^ Description ^
-You can edit as many config files as you like, and then issue reload_config, procd will take care of reloading all of them.   Note, no change in the config file, no reload.  If you want to explicitly reload, you still need to issue '''/etc/init.d/<yourservice> reload''' manually.
+| procd_add_reload_trigger           | list of config files | ''config.change'' | Uses ''/etc/init.d/<foo> reload'' as the handler |
+| procd_add_reload_interface_trigger | interface name       | ''interface.*''   | Uses ''/etc/init.d/<foo> reload'' as the handler |
+| procd_add_reload_mount_trigger     | paths to watch for   | ''mount.add''     | Uses ''/etc/init.d/<foo> reload'' as the handler |
+| procd_add_restart_mount_trigger    | paths to watch for   | ''mount.add''     | Uses ''/etc/init.d/<foo> restart'' as the handler |
-By default, "reload" will cause a stop/start call, _only_ if the md5sum of the final computed command line has changed.  (This is in addition to any reload triggers)  If your application doesn't use args, but has a generated config file, or parses the uci config file directly, you should add that to procd via '''procd_set_param file /var/etc/your_service.conf''' or '''procd_set_param file /etc/config/yourapp''' If you don't have any files or args, but still need to explicitly restart when reload is called, you can hook reload_service as shown below.  Note that if your file is not in /etc/config, that '''reload_config''' won't work, but '''/etc/init.d/<service> reload''' will still do the right thing.
+<WRAP important>
+When using ''uci'' from command line ''uci commit'' doesn't generate ''config.change'' event. It requires calling ''reload_config'' afterwards.
+This does not apply to using ''uci'' over ''rpcd'' plugin.
+</WRAP>
-<code>
+<WRAP important>
+Adding ''interface.*'' trigger and having ''/etc/init.d/<foo> reload'' called won't automatically make ''procd'' notice any state change and won't make it restart a service.
+Relevant interface has to be made part of service state using the ''procd_set_param netdev''.
+</WRAP>
+<WRAP important>
+Using mount triggers depends on mount notifications emitted by ''blockd''. Hence ''blockd'' needs to be installed and the mount need to be configured in ''/etc/config/fstab''.
+See also [[:docs:guide-user:storage:fstab]]
+</WRAP>
+See use cases of [[https://github.com/openwrt/packages/search?q=procd_add_interface_trigger|procd_add_interface_trigger]], [[https://github.com/openwrt/packages/search?q=procd_add_reload_trigger|procd_add_reload_trigger]], [[https://github.com/openwrt/packages/search?q=procd_add_reload_mount_trigger|procd_add_reload_mount_trigger]] in the OpenWrt packages repository.
+==== ucitrack ====
+In older versions of OpenWrt, a system called "ucitrack" attempted to track UCI config files, and the processes that depended on each of them, and would restart them all as needed.  This too, is replaced with ubus/procd, and expanded to allow notifying services when network interfaces change.
+===== Manual reload =====
+Sometimes service state may depend on information that doesn't have any events related. This may happen e.g. with service native configuration files that don't get build using UCI config.
+In such cases ''procd'' should be told to use relevant config file using ''procd_set_param file /etc/foo.conf''. After every config file modification ''/etc/init.d/foo reload'' should be called manually.
+===== Custom service reload =====
+By default (without ''reload_service()'' specified) calling ''/etc/init.d/<foo> reload'' results in running ''service_start()'' and ''procd'' comparing states. In some cases a more complete control over ''reload'' action may be needed thought.
+==== Forcing service restart ====
+If some service requires a restart when ''reload'' is called, it can be implemented as follows:
+<code bash>
 reload_service()
 {
@@ Line 74: / Line 152: @@
 </code>
-If you want/need your service to depend on changes to networking, simply modify your service_triggers section, like so..
+j==== Reloading service setup ====
-<code>
-service_triggers()
+Some services may support reloading configuration without a complete restart. It's usually implemented using `SIGHUP` or similar signal.
-{
-        procd_add_reload_trigger "uci-file-name" "second-uci-file"
-        procd_add_interface_trigger "interface.*" <interface> /etc/init.d/<service> reload
-}
-</code>
-See use cases of [[https://github.com/openwrt/packages/search?q=procd_add_interface_trigger|procd_add_interface_trigger]] and [[https://github.com/openwrt/packages/search?q=procd_add_reload_trigger|procd_add_reload_trigger]] in the OpenWrt packages repository.
-=== Signalling a service ===
+OpenWrt comes with a ''procd_send_signal()'' helper that doesn't require passing PID directly. Example:
-Current versions (LEDE 17.01 and up) support sending signals to procd registered services.  (OpenWrt-CC gained support for pidfile writing, which allowed third party monitoring services to send signals)  This allows, for instance, ''reload_config'' and ''/etc/init.d/yourapp reload'' to issue a SIGHUP instead of stop/starting your process.
 <code>
@@ Line 92: / Line 163: @@
 }
 </code>
-The //signal// is **''SIGHUP''** by default, and must be specified by NAME.  (You can get available signals from ''kill -l'' on the console)
-The //service_name// is the basename of the init.d script, eg for ''/etc/init.d/yourapp'' => ''yourapp''.
+The //signal// argument is ''SIGHUP'' by default and must be specified by NAME. You can get available signals using ''kill -l''.
-The //instance_name// if you wish to signal different instances of your service, comes from the optional parameter to ''procd_open_instance [instance_name]''.  If //instance_name// is unspecified, or '' '*' '' then the signal will be delivered to all instances of the service.
+The //service_name// is the basename of the ''init.d'' script, e.g. ''yourapp'' for the ''/etc/init.d/yourapp''.
+The //instance_name// allows specifying custom instance name in case it was used like ''procd_open_instance [instance_name]''. If //instance_name// is unspecified, or '' '*' '' then the signal will be delivered to all instances of the service.
 **Note** You can also send signals to named procd services from outside initscripts.  Simply load the procd functions and send the signal as before.
@@ Line 105: / Line 177: @@
 </code>
-===== How do these scripts work? =====
+<WRAP important>
-All arguments are packed into json and send over to procd via ubus
+You can also configure reload by signal with ''procd_set_param reload_signal'' service option.
+</WRAP>
+===== Service jails =====
+procd can isolate services using various Linux features typically used for (slim-)containers: //chroot// and //namespaces// (and //limits//, //seccomp//, //capabilities// as well as setting ''PR_SET_NO_NEW_PRIVS'', see [[#service_parameters|Service Parameters]]).
+^ Function                ^ Arguments            ^ Description                                                        ^
+| procd_add_jail          | jail name, flags     | Set up service jail (with features according to //flags//)          |
+| procd_add_jail_mount    | read-only paths      | Read-only bind the paths listed to the jail's mount namespace      |
+| procd_add_jail_mount_rw | read-write paths     | Bind the paths listed to the jail's mount namespace                |
+^ Flag        ^ Description                                                      ^
+| log         | Allow jailed service to log to syslog                            |
+| ubus        | Allow jailed service to access ubus                              |
+| procfs      | Mount /proc in jail                                              |
+| sysfs       | Mount /sys in jail                                               |
+| ronly       | Re-mount jail rootfs read-only                                   |
+| requirejail | Do not fall back to run without jail in case jail could not be set up |
+| netns       | Run jailed process in new network namespace                      |
+| userns      | Run jailed process in new user namespace                         |
+| cgroupsns   | Run jailed process in new cgroups namespace                      |
+| console     | Set up console accessible with ''ujail-console''                 |
+See use cases of [[https://github.com/openwrt/packages/search?q=procd_add_jail|procd_add_jail]].
 ===== Debugging =====
 Set PROCD_DEBUG=1 to see debugging information when starting or stopping a procd init script.
 Also, ''INIT_TRACE=1 /etc/init.d/mything $action'' Where $action is start/stop etc.
 ===== Examples =====
@@ Line 126: / Line 222: @@
 | ''env'' | Key-Value-List | Sets a number of environment variables in ''key=value'' notation exported to the spawned process. |
 | ''data'' | Key-Value-List | Sets arbitrary user data in ''key=value'' notation to the ubus service state. This is mainly used to store additional meta data with spawned services, such as mDNS announcements or firewall rules which may be picked up by other services. |
-| ''limits'' | Key-Value-List | Set ulimit values in ''key=value'' notation for the spawned process. The following limit names are recognized by //procd//: ''as'' (''RLIMIT_AS''), ''core'' (''RLIMIT_CORE''), ''cpu'' (''RLIMIT_CPU''), ''data'' (''RLIMIT_DATA''), ''fsize'' (''RLIMIT_FSIZE''), ''memlock'' (''RLIMIT_MEMLOCK''), ''nofile'' (''RLIMIT_NOFILE''), ''nproc'' (''RLIMIT_NPROC''), ''rss'' (''RLIMIT_RSS''), ''stack'' (''RLIMIT_STACK''), ''nice'' (''RLIMIT_NICE''), ''rtprio'' (''RLIMIT_RTPRIO''), ''msgqueue'' (''RLIMIT_MSGQUEUE''), ''sigpending'' (''RLIMIT_SIGPENDING'') |
+| ''limits'' | Key-Value-List | Set ulimit values in ''key=value'' notation for the spawned process. The following limit names are recognized by //procd//: ''as'' (''RLIMIT_AS''), ''core'' (''RLIMIT_CORE''), ''cpu'' (''RLIMIT_CPU''), ''data'' (''RLIMIT_DATA''), ''fsize'' (''RLIMIT_FSIZE''), ''memlock'' (''RLIMIT_MEMLOCK''), ''nofile'' (''RLIMIT_NOFILE''), ''nproc'' (''RLIMIT_NPROC''), ''rss'' (''RLIMIT_RSS''), ''stack'' (''RLIMIT_STACK''), ''nice'' (''RLIMIT_NICE''), ''rtprio'' (''RLIMIT_RTPRIO''), ''msgqueue'' (''RLIMIT_MSGQUEUE''), ''sigpending'' (''RLIMIT_SIGPENDING'') **Two numeric values, separated by blank space, are expected for RLIMIT: the first value represents the soft limit and the other the hard limit; e.g.: procd_set_param limits nofile="10000 20000"; the "unlimited" value can be used in cases where "ulimit -{parameter} unlimited" works, for example for the "core" parameter.**|
 | ''command'' | List | Sets the command vector (''argv'') used to execute the process. |
 | ''netdev'' | List | Passes a list of Linux network device names to //procd// to be monitored for changes. Upon starting a service, the interface index of each network device name is resolved and stored as part of //procd//'s in-memory service state. When a service reload request is processed and the interface index of any of the associated network devices changed or if the list itself changed, the running service state is invalidated and //procd// will restart the associated process or deliver a UNIX signal to it, depending on how the service was set up. |
@@ Line 138: / Line 234: @@
 | ''pidfile'' | String | Instructs //procd// to write the PID of the spawned process into the specified file path. While //procd// itself does not use or require PID files to track spawned processes, this option is useful for sitation where knowledge of the PID is required, e.g. for monitoring or control client software. |
 | ''user'' | String | Specifies the name of the user to spawn the process as. //procd// will look up the given name in ''/etc/passwd'' and set the effective uid and primary gid of the spawned processaccordingly. If omitted, the process is spawned as ''root'' (uid 0, gid 0) |
-| ''seccomp'' | String | Specifies the ''seccomp'' list for //ujail// (''ujail -S'') |
+| ''seccomp'' | String | Specifies file path to read seccomp filter rules from, the file should be JSON formatted like the [[https://github.com/opencontainers/runtime-spec/blob/master/config-linux.md#seccomp|seccomp object of the OCI run-time spec]] |
-| ''capabilities'' | String | This parameter is currently unused. |
+| ''capabilities'' | String | Specifies file path to read capability set, the file should be JSON formatted like the [[https://github.com/opencontainers/runtime-spec/blob/master/config.md#linux-process|capabilities object of the OCI run-time spec]]|
 | ''stdout'' | Boolean | If set to ''1'', instruct //procd// to relay the spawned process' stdout to the system log. The stdout will be fed line-wise to ''syslog(3)'' using the basename of the first command argument as identity, ''LOG_INFO'' as priority and ''LOG_DAEMON'' as facility. |
 | ''stderr'' | Boolean | If set to ''1'', instruct //procd// to relay the spawned process' stderr to the system log. The stderr will be fed line-wise to ''syslog(3)'' using the basename of the first command argument as identity, ''LOG_ERR'' as priority and ''LOG_DAEMON'' as facility. |
 | ''no_new_privs'' | Boolean | Instructs //ujail// to not allow privilege elevation. Sets the //ujail// ''-c'' parameter when true. |