From 7732f92bad5f24a4bd03bb357af46da56b0ac94d Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Wed, 3 Feb 2016 20:32:06 +0100 Subject: nspawn: optionally run a stub init process as PID 1 This adds a new switch --as-pid2, which allows running commands as PID 2, while a stub init process is run as PID 1. This is useful in order to run arbitrary commands in a container, as PID1's semantics are different from all other processes regarding reaping of unknown children or signal handling. --- man/systemd-nspawn.xml | 65 +++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 59 insertions(+), 6 deletions(-) (limited to 'man/systemd-nspawn.xml') diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml index 1cfef93df1..86cdb4e124 100644 --- a/man/systemd-nspawn.xml +++ b/man/systemd-nspawn.xml @@ -248,16 +248,69 @@ . + + + + + Invoke the shell or specified program as process ID (PID) 2 instead of PID 1 (init). By + default, if neither this option nor is used, the selected binary is run as process with + PID 1, a mode only suitable for programs that are aware of the special semantics that the process with PID 1 + has on UNIX. For example, it needs to reap all processes reparented to it, and should implement + sysvinit compatible signal handling (specifically: it needs to reboot on SIGINT, reexecute + on SIGTERM, reload configuration on SIGHUP, and so on). With a minimal stub init + process is run as PID 1 and the selected binary is executed as PID 2 (and hence does not need to implement any + special semantics). The stub init process will reap processes as necessary and react appropriately to + signals. It is recommended to use this mode to invoke arbitrary commands in containers, unless they have been + modified to run correctly as PID 1. Or in other words: this switch should be used for pretty much all commands, + except when the command refers to an init or shell implementation, as these are generally capable of running + correctly as PID 1). This option may not be combined with or + . + + + - Automatically search for an init binary and - invoke it instead of a shell or a user supplied program. If - this option is used, arguments specified on the command line - are used as arguments for the init binary. This option may not - be combined with . - + Automatically search for an init binary and invoke it as PID 1, instead of a shell or a user + supplied program. If this option is used, arguments specified on the command line are used as arguments for the + init binary. This option may not be combined with or + . + + The following table explains the different modes of invocation and relationship to + (see above): + + + Invocation Mode + + + + + + Switch + Explanation + + + + + Neither nor specified + The passed parameters are interpreted as command line, which is executed as PID 1 in the container. + + + + specified + The passed parameters are interpreted as command line, which are executed as PID 2 in the container. A stub init process is run as PID 1. + + + + specified + An init binary as automatically searched and run as PID 1 in the container. The passed parameters are used as invocation parameters for this process. + + + + +
+ -- cgit v1.2.3-54-g00ecf