diff --git a/man/systemd-run.xml b/man/systemd-run.xml index 149228ee02..6c15d2d837 100644 --- a/man/systemd-run.xml +++ b/man/systemd-run.xml @@ -83,6 +83,16 @@ COMMAND may be omitted. In this case, systemd-run creates only a .path, .socket, or .timer unit that triggers the specified unit. + + By default, services created with systemd-run default to the type, + see the description of Type= in + systemd.service5 for + details. Note that when this type is used the service manager (and thus the systemd-run command) + considers service start-up successful as soon as the fork() for the main service process + succeeded, i.e. before the execve() is invoked, and thus even if the specified command cannot + be started. Consider using the service type (i.e. ) to + ensure that systemd-run returns successfully only if the specified command line has been + successfully started. diff --git a/man/systemd.service.xml b/man/systemd.service.xml index f14a057280..0cd5385f9b 100644 --- a/man/systemd.service.xml +++ b/man/systemd.service.xml @@ -153,77 +153,93 @@ Type= - Configures the process start-up type for this - service unit. One of - , - , - , - , - or - . + + Configures the process start-up type for this service unit. One of , + , , , , + or : - If set to (the default if - neither Type= nor - BusName=, but ExecStart= - are specified), it is expected that the process configured - with ExecStart= is the main process of the - service. In this mode, if the process offers functionality to - other processes on the system, its communication channels - should be installed before the daemon is started up (e.g. - sockets set up by systemd, via socket activation), as systemd - will immediately proceed starting follow-up units. + + If set to (the default if ExecStart= is + specified but neither Type= nor BusName= are), the service manager + will consider the unit started immediately after the main service process has been forked off. It is + expected that the process configured with ExecStart= is the main process of the + service. In this mode, if the process offers functionality to other processes on the system, its + communication channels should be installed before the service is started up (e.g. sockets set up by + systemd, via socket activation), as the service manager will immediately proceed starting follow-up units, + right after creating the main service process, and before executing the service's binary. Note that this + means systemctl start command lines for services will report + success even if the service's binary cannot be invoked successfully (for example because the selected + User= doesn't exist, or the service binary is missing). - If set to , it is expected that - the process configured with ExecStart= will - call fork() as part of its start-up. The - parent process is expected to exit when start-up is complete - and all communication channels are set up. The child continues - to run as the main daemon process. This is the behavior of - traditional UNIX daemons. If this setting is used, it is - recommended to also use the PIDFile= - option, so that systemd can identify the main process of the - daemon. systemd will proceed with starting follow-up units as - soon as the parent process exits. + The type is similar to , but the service + manager will consider the unit started immediately after the main service binary has been executed. The service + manager will delay starting of follow-up units until that point. (Or in other words: + proceeds with further jobs right after fork() returns, while + will not proceed before both fork() and + execve() in the service process succeeded.) Note that this means systemctl + start command lines for services will report failure when the service's + binary cannot be invoked successfully (for example because the selected User= doesn't + exist, or the service binary is missing). - Behavior of is similar to - ; however, it is expected that the - process has to exit before systemd starts follow-up units. - RemainAfterExit= is particularly useful for - this type of service. This is the implied default if neither - Type= nor ExecStart= are - specified. + If set to , it is expected that the process configured with + ExecStart= will call fork() as part of its start-up. The parent + process is expected to exit when start-up is complete and all communication channels are set up. The child + continues to run as the main service process, and the service manager will consider the unit started when + the parent process exits. This is the behavior of traditional UNIX services. If this setting is used, it is + recommended to also use the PIDFile= option, so that systemd can reliably identify the + main process of the service. systemd will proceed with starting follow-up units as soon as the parent + process exits. - Behavior of is similar to - ; however, it is expected that the - daemon acquires a name on the D-Bus bus, as configured by - BusName=. systemd will proceed with - starting follow-up units after the D-Bus bus name has been - acquired. Service units with this option configured implicitly - gain dependencies on the dbus.socket - unit. This type is the default if BusName= - is specified. + Behavior of is similar to ; however, the + service manager will consider the unit started after the main process exits. It will then start follow-up + units. RemainAfterExit= is particularly useful for this type of + service. Type= is the implied default if neither + Type= nor ExecStart= are specified. - Behavior of is similar to - ; however, it is expected that the - daemon sends a notification message via - sd_notify3 - or an equivalent call when it has finished starting up. - systemd will proceed with starting follow-up units after this - notification message has been sent. If this option is used, - NotifyAccess= (see below) should be set to - open access to the notification socket provided by systemd. If - NotifyAccess= is missing or set to - , it will be forcibly set to - . Note that currently - Type= will not work - if used in combination with - PrivateNetwork=. + Behavior of is similar to ; however, it is + expected that the service acquires a name on the D-Bus bus, as configured by + BusName=. systemd will proceed with starting follow-up units after the D-Bus bus name + has been acquired. Service units with this option configured implicitly gain dependencies on the + dbus.socket unit. This type is the default if BusName= is + specified. - Behavior of is very similar to ; however, actual execution - of the service program is delayed until all active jobs are dispatched. This may be used to avoid interleaving - of output of shell services with the status output on the console. Note that this type is useful only to - improve console output, it is not useful as a general unit ordering tool, and the effect of this service type - is subject to a 5s time-out, after which the service program is invoked anyway. + Behavior of is similar to ; however, it is + expected that the service sends a notification message via + sd_notify3 or an + equivalent call when it has finished starting up. systemd will proceed with starting follow-up units after + this notification message has been sent. If this option is used, NotifyAccess= (see + below) should be set to open access to the notification socket provided by systemd. If + NotifyAccess= is missing or set to , it will be forcibly set to + . Note that currently Type= will not work if + used in combination with PrivateNetwork=. + + Behavior of is very similar to ; however, + actual execution of the service program is delayed until all active jobs are dispatched. This may be used + to avoid interleaving of output of shell services with the status output on the console. Note that this + type is useful only to improve console output, it is not useful as a general unit ordering tool, and the + effect of this service type is subject to a 5s time-out, after which the service program is invoked + anyway. + + + It is generally recommended to use Type= for long-running + services whenever possible, as it is the simplest and fastest option. However, as this service type won't + propagate service start-up failures and doesn't allow ordering of other units against completion of + initialization of the service (which for example is useful if clients need to connect to the service through + some form of IPC, and the IPC channel is only established by the service itself — in contrast to doing this + ahead of time through socket or bus activation or similar), it might not be sufficient for many cases. If so, + or (the latter only in case the service provides a D-Bus + interface) are the preferred options as they allow service program code to precisely schedule when to + consider the service started up successfully and when to proceed with follow-up units. The + service type requires explicit support in the service codebase (as + sd_notify() or an equivalent API needs to be invoked by the service at the appropriate + time) — if it's not supported, then is an alternative: it supports the traditional + UNIX service start-up protocol. Finally, might be an option for cases where it is + enough to ensure the service binary is invoked, and where the service binary itself executes no or little + initialization on its own (and its initialization is unlikely to fail). Note that using any type other than + possibly delays the boot process, as the service manager needs to wait for service + initialization to complete. It is hence recommended not to needlessly use any types other than + . (Also note it is generally not recommended to use or + for long-running services.)