[Buildroot] [PATCH 1/2] package/tini: restore use as docker-init

[Buildroot] [PATCH 1/2] package/tini: restore use as docker-init

[Fiona Klute via buildroot]

From: "Fiona Klute (WIWA)" <fiona.klute@gmx.de>

Commit 24cac9c4e6a36fd14b263a8eecf7ae7d58ab5a59 "system: add tini as
init system" made BR2_PACKAGE_TINI depend on BR2_INIT_TINI. This is
incorrect: tini is not only needed when building a container image
using Buildroot, but also to run Docker containers on Buildroot
systems using another another init system, if Docker is configured to
provide an init process for the container (e.g. with "docker run
--init"). The tini package already provides the "docker-init" symlink
required for that.

Example error without tini installed:

$ docker run --rm -ti --init alpine
docker: Error response from daemon: exec: "docker-init": executable file not found in $PATH.

Signed-off-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
---
 package/tini/Config.in | 1 -
 1 file changed, 1 deletion(-)

diff --git a/package/tini/Config.in b/package/tini/Config.in
index bca8ad8e96..719e1e1f22 100644
--- a/package/tini/Config.in
+++ b/package/tini/Config.in
@@ -1,7 +1,6 @@
 config BR2_PACKAGE_TINI
 	bool "tini"
 	depends on BR2_USE_MMU # fork()
-	depends on BR2_INIT_TINI
 	help
 	  tini is a simple but valid init binary to
 	  act as PID 1 for containers.
--
2.45.2

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[Buildroot] [PATCH 2/2] package/docker-engine: add optional dependency on tini

[Fiona Klute via buildroot]

From: "Fiona Klute (WIWA)" <fiona.klute@gmx.de>

To provide an init process for containers if requested e.g. with
"docker run --init", Docker relies on tini to provide the init
binary. package/tini already provides the required
/usr/libexec/docker/docker-init symlink, the new option just selects
tini if enabled to prevent confusion over why docker-init is missing.

Signed-off-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
---
Adding an option seems like the least invasive version to me. An
unconditional dependency would work too, I'd be surprised if anyone
using Docker on the target has an issue with the extra ~66KB. Or drop
the patch, being able to install tini (patch 1) is the critical
part. ;-)

 package/docker-engine/Config.in | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/package/docker-engine/Config.in b/package/docker-engine/Config.in
index 49a002a647..e03ecceeff 100644
--- a/package/docker-engine/Config.in
+++ b/package/docker-engine/Config.in
@@ -48,6 +48,17 @@ config BR2_PACKAGE_DOCKER_ENGINE_DRIVER_VFS
 	help
 	  Build the vfs filesystem driver for Docker.

+config BR2_PACKAGE_DOCKER_ENGINE_DOCKER_INIT
+	bool "support docker-init"
+	select BR2_PACKAGE_TINI # runtime
+	help
+	  Support providing a minimal init process for containers,
+	  using tini. Required to use "docker run --init".
+
+	  This does not change the Docker engine build, the
+	  docker-init symlink is provided by the tini package
+	  itself. This option only adds the dependency.
+
 endif

 comment "docker-engine needs a glibc or musl toolchain w/ threads, headers >= 3.17"
--
2.45.2

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Re: [Buildroot] [PATCH 1/2] package/tini: restore use as docker-init

[Christian Stewart via buildroot]

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Hi all,

On Thu, Oct 10, 2024, 6:29 AM Fiona Klute <fiona.klute@gmx.de> wrote:

> From: "Fiona Klute (WIWA)" <fiona.klute@gmx.de>
>
> Commit 24cac9c4e6a36fd14b263a8eecf7ae7d58ab5a59 "system: add tini as
> init system" made BR2_PACKAGE_TINI depend on BR2_INIT_TINI. This is
> incorrect: tini is not only needed when building a container image
> using Buildroot, but also to run Docker containers on Buildroot
> systems using another another init system, if Docker is configured to
> provide an init process for the container (e.g. with "docker run
> --init"). The tini package already provides the "docker-init" symlink
> required for that.
>
> Example error without tini installed:
>
> $ docker run --rm -ti --init alpine
> docker: Error response from daemon: exec: "docker-init": executable file
> not found in $PATH.
>
> Signed-off-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
> ---
>  package/tini/Config.in | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/package/tini/Config.in b/package/tini/Config.in
> index bca8ad8e96..719e1e1f22 100644
> --- a/package/tini/Config.in
> +++ b/package/tini/Config.in
> @@ -1,7 +1,6 @@
>  config BR2_PACKAGE_TINI
>         bool "tini"
>         depends on BR2_USE_MMU # fork()
> -       depends on BR2_INIT_TINI
>         help
>           tini is a simple but valid init binary to
>           act as PID 1 for containers.
>

Agreed

Reviewed-by: Christian Stewart <christian@aperture.us>

Best regards,
Christian

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Re: [Buildroot] [PATCH 1/2] package/tini: restore use as docker-init

[Thomas Petazzoni via buildroot]

On Thu, 10 Oct 2024 15:29:11 +0200
Fiona Klute via buildroot <buildroot@buildroot.org> wrote:

> From: "Fiona Klute (WIWA)" <fiona.klute@gmx.de>
> 
> Commit 24cac9c4e6a36fd14b263a8eecf7ae7d58ab5a59 "system: add tini as
> init system" made BR2_PACKAGE_TINI depend on BR2_INIT_TINI. This is
> incorrect: tini is not only needed when building a container image
> using Buildroot, but also to run Docker containers on Buildroot
> systems using another another init system, if Docker is configured to
> provide an init process for the container (e.g. with "docker run
> --init"). The tini package already provides the "docker-init" symlink
> required for that.
> 
> Example error without tini installed:
> 
> $ docker run --rm -ti --init alpine
> docker: Error response from daemon: exec: "docker-init": executable file not found in $PATH.
> 
> Signed-off-by: Fiona Klute (WIWA) <fiona.klute@gmx.de>
> ---
>  package/tini/Config.in | 1 -
>  1 file changed, 1 deletion(-)

Thanks, both applied. On PATCH 2/2, I wasn't 100% sure, but it's simple
enough, clarifies this dependency that isn't entirely obvious, and can
always be reworked/reverted if other people think it wasn't the right
solution.

Thomas
-- 
Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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