Add --requires flag to podman run/create

Podman has, for a long time, had an internal concept of
dependency management, used mainly to ensure that pod infra
containers are started before any other container in the pod. We
also have the ability to recursively start these dependencies,
which we use to ensure that `podman start` on a container in a
pod will not fail because the infra container is stopped. We have
not, however, exposed these via the command line until now.

Add a `--requires` flag to `podman run` and `podman create` to
allow users to manually specify dependency containers. These
containers must be running before the container will start. Also,
make recursive starting with `podman start` default so we can
start these containers and their dependencies easily.

Fixes #9250

Signed-off-by: Matthew Heon <matthew.heon@pm.me>

1 files changed, 26 insertions, 1 deletions

diff --git a/docs/source/markdown/podman-create.1.md b/docs/source/markdown/podman-create.1.md
index 9ae4ab207..9e7fa4bfd 100644
--- a/docs/source/markdown/podman-create.1.md
+++ b/docs/source/markdown/podman-create.1.md
@@ -781,6 +781,12 @@ If container is running in --read-only mode, then mount a read-write tmpfs on /r
 
 If another container with the same name already exists, replace and remove it. The default is **false**.
 
+#### **\-\-requires**=**container**
+
+Specify one or more requirements.
+A requirement is a dependency container that will be started before this container.
+Containers can be specified by name or ID, with multiple containers being separated by commas.
+
 #### **\-\-restart**=*policy*
 
 Restart policy to follow when containers exit.
@@ -1254,6 +1260,25 @@ $ podman create --tz=Asia/Shanghai alpine date
 $ podman create --tz=US/Eastern alpine date
 ```
 
+### Adding dependency containers
+
+Podman will make sure the first container, container1, is running before the second container (container2) is started.
+
+```
+$ podman create --name container1 -t -i fedora bash
+$ podman create --name container2 --requires container1 -t -i fedora bash
+$ podman start --attach container2
+```
+
+Multiple containers can be required.
+
+```
+$ podman create --name container1 -t -i fedora bash
+$ podman create --name container2 -t -i fedora bash
+$ podman create --name container3 --requires container1,container2 -t -i fedora bash
+$ podman start --attach container3
+```
+
 ### Rootless Containers
 
 Podman runs as a non root user on most systems. This feature requires that a new enough version of shadow-utils
@@ -1301,7 +1326,7 @@ b
 NOTE: Use the environment variable `TMPDIR` to change the temporary storage location of downloaded container images. Podman defaults to use `/var/tmp`.
 
 ## SEE ALSO
-**podman**(1), **podman-secret**(1), **podman-save**(1), **podman-ps**(1), **podman-attach**(1), **podman-pod-create**(1), **podman-port**(1), **podman-kill**(1), **podman-stop**(1),
+**podman**(1), **podman-secret**(1), **podman-save**(1), **podman-ps**(1), **podman-attach**(1), **podman-pod-create**(1), **podman-port**(1), **podman-start*(1), **podman-kill**(1), **podman-stop**(1),
 **podman-generate-systemd**(1) **podman-rm**(1), **subgid**(5), **subuid**(5), **containers.conf**(5), **systemd.unit**(5), **setsebool**(8), **slirp4netns**(1), **fuse-overlayfs**(1), **proc**(5)**.
 
 ## HISTORY