[Buildroot] [PATCH 4/6] package/pseudo: expose the host binary in a variable

[Arnout Vandecappelle]

On 07-11-16 22:23, Yann E. MORIN wrote:
> Running pseudo is more involved than running fakeroot. In the transition
> from using fakeroot, we just did not account for the extra requirements.
> 
> First, we explicitly tell pseudo where it is, otherwise it tries to
> guess. Its guess is correct, but it prints a warning, which is not nice.
> 
> Second, we tell it where to find the passwd and group files in case it
> has to emulate access to them. We currently do not use that feature, but
> better safe than sorry.
> 
> Third, pseudo spawns a background daemon, and talks to it (when fakeroot
> would emulate the state all in the current process' state, pseudo uses
> the daemon to coordinate the state across multiple processes). We are
> not much interested in the daemon lingering around, so we just tell it
> to termintate as soon as the last clients quits (this can take up to one
> second).
> 
> Fourth and last, pseudo always stores its internal database when
> exiting, and reloads it when spawned. The database is by default stored
> in a sub-directory of the prefix it was installed in, but this is
> impractical for us, in case the host-dir is outside the config dir
> $(BASE_DIR). We want the database to be specific to the one config dir

 $(HOST_DIR), even if outside of $(BASE_DIR), must also be specific to one
config dir. Remember that $(STAGING_DIR) resides under $(HOST_DIR). So this
argument is not really valid. However, I do fully agree that
$(HOST_DIR)/usr/var/pseudo is *not* the best place for it, and that your
proposed location is better.

> we are building. So, we store the database in a (hidden) sub-dir of the
> build dir, thus ensuring it is never shared with another build.

 I would like to add the following:

We pass these options as environment variables in the pseudo invocation,
nicely wrapped in the HOST_PSEUDO variable. An alternative would be to
create a pseudo wrapper script, but that is less attractive for the
following reasons.

- We don't expect users to need to call pseudo from post-build/image
  scripts, because we already support BR2_ROOTFS_POST_FAKEROOT_SCRIPT.

- Creating a script is a bit more complicated, e.g. with relocatable
  host directory in mind.


> 
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
> Cc: Gaël PORTAY <gael.portay at savoirfairelinux.com>
> Cc: Patrick Keroulas <patrick.keroulas at savoirfairelinux.com>
> Cc: Erico Nunes <nunes.erico at gmail.com>
> Cc: Julien BOIBESSOT <julien.boibessot at free.fr>

Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout at mind.be>

... but I like my bikeshed to be coloured differently...

> ---
>  package/pseudo/pseudo.mk | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/package/pseudo/pseudo.mk b/package/pseudo/pseudo.mk
> index 98c7de5..2a3e31f 100644
> --- a/package/pseudo/pseudo.mk
> +++ b/package/pseudo/pseudo.mk
> @@ -23,6 +23,13 @@ HOST_PSEUDO_CONF_OPTS = \
>  	--libdir=$(HOST_DIR)/usr/lib \
>  	--with-sqlite=$(HOST_DIR)/usr
>  
> +HOST_PSEUDO = \

 We use $(MAKE), $(TAR), $(QT_QMAKE), $(QT5_QMAKE), $(BR2_CMAKE), $(LUA_RUN),
$(PERL_RUN). Nowhere do we use $(HOST_FOO) to define a command. I admit that all
of these are not completely consistent, but I think the _RUN pattern fits best
for this situation, so how about PSEUDO_RUN?

> +	PSEUDO_PREFIX=$(HOST_DIR)/usr \
> +	PSEUDO_PASSWD=$(TARGET_DIR) \
> +	PSEUDO_OPTS=-t0 \
> +	PSEUDO_LOCALSTATEDIR=$(BUILD_DIR)/.pseudodb \

 I don't really like hidden files/directories in BUILD_DIR. I was thinking more
along the lines of $(BASE_DIR)/target-pseudodb. But I'm OK with your proposal as
well.

> +	$(HOST_DIR)/usr/bin/pseudo

 Perhaps it's better to provide the options on the command line, as far as
possible. So
	PSEUDO_PASSWD=$(TARGET_DIR) \
	PSEUDO_LOCALSTATEDIR=$(BUILD_DIR)/.pseudodb \
	$(HOST_DIR)/usr/bin/pseudo -t0 -P $(HOST_DIR)/usr


 Regards,
 Arnout

> +
>  define HOST_PSEUDO_FAKEROOT_SYMLINK
>  	ln -sf pseudo $(HOST_DIR)/usr/bin/fakeroot
>  endef
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
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