diff mbox

[PATCHv3] system: add options for /bin /sbin and /lib to be symlinks into /usr

Message ID 1441397852-23461-1-git-send-email-yann.morin.1998@free.fr
State Accepted
Headers show

Commit Message

Yann E. MORIN Sept. 4, 2015, 8:17 p.m. UTC
systemd is increasingly expecting things to live in /usr/bin, /usr/sbin
or /usr/lib nad not in /bin, /sbin or /lib. It has inherited those
expectations from a Fedora change:
    https://fedoraproject.org/wiki/Features/UsrMove

Note however, that systemd does support /usr being on a separate
filesystem; it just expects an initramfs to mount it before the final
switchroot over to the actual rootfs.

But the traditional use-case for Buildroot is not to boot with an
initramfs; although that is totally feasible, that's probably not what
is commonly done in the vast majority of cases.

However, a lot of packages still install stuff directly into /bin,
/sbin or /lib, which systemd may need early-on in the boot process,
even before it may have a chance to mount /usr. Even though we can
tell systemd, at configure-time, where it should expect programs to
be at runtime, it does not make sense to go head-first against an
upstream wa^Hill.

Add an option so that /bin, /sbin and /lib be symlinks to /usr/bin
and /usr/sbin. That option is forcibly enabled when the init system
is systemd.

Note: we need not handle /lib32 or /lib64, as they already are symlinks
to /lib, which means they will automatically be redirected to /usr/lib,
as /usr/lib32 and /usr/lib64 already are.

Furthermore, this means we're no longer supporting a split-usr setup, so
the corresponding configure options have been removed as well for
systemd and, when using a merged /usr, for eudev as well.

In Buildroot, we decided (with this patch) not to support a split-usr
when systemd is used as an init system. This is a design decision, not
a systemd issue. Thus the select is with BR2_INIT_SYSTEMD rather than
with BR2_PACKAGE_SYSTEMD.

Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Cc: Arnout Vandecappelle <arnout@mind.be>
Cc: Mike Williams <mike@mikebwilliams.com>
Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
Cc: Baruch Siach <baruch@tkos.co.il>

---
Changes v2 -> v3:
  - only conditionally drop the split-usr options for eudev  (Vicente)
  - add this missing history log  (Vicente)
  - add a rationale on why this is the init system that selects
    merged-usr, not the package  (Arnout).

Changes v1 -> v2:
  - in skeleton.mk, use a single variable for both cases  (Arnout)
  - add reference to the Fedora merged-usr manifesto  (Arnout)
  - add note about /lib32 and /lib64  (Arnout)
  - rename the kconfig option  (Arnout)
  - slightly reword the help text  (Arnout)
  - drop the split-usr and related options from systemd (Mike, Vicente)
    and eudev (but only when using merged-usr)
  - typoes  (Arnout, Baruch)
---
 package/eudev/eudev.mk       |  6 ++++--
 package/skeleton/skeleton.mk | 20 +++++++++++++++++---
 package/systemd/systemd.mk   |  2 --
 system/Config.in             | 17 +++++++++++++++++
 system/skeleton/bin/.empty   |  0
 system/skeleton/lib/.empty   |  0
 system/skeleton/sbin/.empty  |  0
 7 files changed, 38 insertions(+), 7 deletions(-)
 delete mode 100644 system/skeleton/bin/.empty
 delete mode 100644 system/skeleton/lib/.empty
 delete mode 100644 system/skeleton/sbin/.empty

diff --git a/system/skeleton/bin/.empty b/system/skeleton/bin/.empty
deleted file mode 100644
index e69de29..0000000
diff --git a/system/skeleton/lib/.empty b/system/skeleton/lib/.empty
deleted file mode 100644
index e69de29..0000000
diff --git a/system/skeleton/sbin/.empty b/system/skeleton/sbin/.empty
deleted file mode 100644
index e69de29..0000000

Comments

Arnout Vandecappelle Sept. 5, 2015, 9:21 a.m. UTC | #1
On 04-09-15 22:17, Yann E. MORIN wrote:
[snip]
> diff --git a/package/eudev/eudev.mk b/package/eudev/eudev.mk
> index 1aa74b3..a005f45 100644
> --- a/package/eudev/eudev.mk
> +++ b/package/eudev/eudev.mk
> @@ -22,16 +22,18 @@ EUDEV_CONF_ENV += LIBS=-lrt
>  EUDEV_CONF_OPTS =		\
>  	--disable-manpages	\
>  	--sbindir=/sbin		\
> -	--with-rootlibdir=/lib	\
>  	--libexecdir=/lib	\
>  	--with-firmware-path=/lib/firmware	\
>  	--disable-introspection			\
> -	--enable-split-usr			\
>  	--enable-libkmod
>  
>  EUDEV_DEPENDENCIES = host-gperf host-pkgconf util-linux kmod
>  EUDEV_PROVIDES = udev
>  
> +ifeq ($(BR2_ROOTFS_MERGED_USR),)
> +EUDEV_CONF_OPTS += --with-rootlibdir=/lib --enable-split-usr
> +endif

 It would be nice if someone could do a runtime test with eudev, both the merged
and the split case.

> +
>  ifeq ($(BR2_PACKAGE_EUDEV_RULES_GEN),y)
>  EUDEV_CONF_OPTS += --enable-rule_generator
>  endif
> diff --git a/package/skeleton/skeleton.mk b/package/skeleton/skeleton.mk
[snip]
>  define SKELETON_INSTALL_TARGET_CMDS
>  	rsync -a --ignore-times $(SYNC_VCS_EXCLUSIONS) \
>  		--chmod=u=rwX,go=rX --exclude .empty --exclude '*~' \
>  		$(SKELETON_PATH)/ $(TARGET_DIR)/
> -	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
> -		$(TARGET_DIR_WARNING_FILE)
> +	$(SKELETON_USR_SYMLINKS_OR_DIRS)
>  	ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
> -	mkdir -p $(TARGET_DIR)/usr

 Huh, where did the mkdir go? Did you remove it because /usr is already in the
skeleton?

>  	ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)
> +	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
> +		$(TARGET_DIR_WARNING_FILE)

 And why did you move this one around?


 Regards,
 Arnout

>  endef
>  
>  SKELETON_TARGET_GENERIC_HOSTNAME = $(call qstrip,$(BR2_TARGET_GENERIC_HOSTNAME))
[snip]
Thomas Petazzoni Sept. 5, 2015, 9:44 a.m. UTC | #2
Hello,

On Sat, 5 Sep 2015 11:21:20 +0200, Arnout Vandecappelle wrote:

> > +ifeq ($(BR2_ROOTFS_MERGED_USR),)
> > +EUDEV_CONF_OPTS += --with-rootlibdir=/lib --enable-split-usr
> > +endif
> 
>  It would be nice if someone could do a runtime test with eudev, both the merged
> and the split case.

I can add some test cases in my testing infrastructure, to test the
eudev merged and split cases, and the systemd case. It makes it a lot
easier than doing manual testing over and over again when you want to
test new iterations of the patches.

Let me know if there is some interest :)

Thanks,

Thomas
Yann E. MORIN Sept. 5, 2015, 12:13 p.m. UTC | #3
Arnout, All,

On 2015-09-05 11:21 +0200, Arnout Vandecappelle spake thusly:
> On 04-09-15 22:17, Yann E. MORIN wrote:
> [snip]
> > diff --git a/package/eudev/eudev.mk b/package/eudev/eudev.mk
> > index 1aa74b3..a005f45 100644
> > --- a/package/eudev/eudev.mk
> > +++ b/package/eudev/eudev.mk
> > @@ -22,16 +22,18 @@ EUDEV_CONF_ENV += LIBS=-lrt
> >  EUDEV_CONF_OPTS =		\
> >  	--disable-manpages	\
> >  	--sbindir=/sbin		\
> > -	--with-rootlibdir=/lib	\
> >  	--libexecdir=/lib	\
> >  	--with-firmware-path=/lib/firmware	\
> >  	--disable-introspection			\
> > -	--enable-split-usr			\
> >  	--enable-libkmod
> >  
> >  EUDEV_DEPENDENCIES = host-gperf host-pkgconf util-linux kmod
> >  EUDEV_PROVIDES = udev
> >  
> > +ifeq ($(BR2_ROOTFS_MERGED_USR),)
> > +EUDEV_CONF_OPTS += --with-rootlibdir=/lib --enable-split-usr
> > +endif
>  It would be nice if someone could do a runtime test with eudev, both the merged
> and the split case.

I did.

The split-usr case is what we have had until now, and it works (I'm
using it daily with Kodi).

The merged-usr case I build-tested and slightly runtime-tested in the
same conditions (Kodi), and could see no difference in behaviour with
the split-usr case.

It's the systemd case that I did not runtime-test (only build-tested).

> >  ifeq ($(BR2_PACKAGE_EUDEV_RULES_GEN),y)
> >  EUDEV_CONF_OPTS += --enable-rule_generator
> >  endif
> > diff --git a/package/skeleton/skeleton.mk b/package/skeleton/skeleton.mk
> [snip]
> >  define SKELETON_INSTALL_TARGET_CMDS
> >  	rsync -a --ignore-times $(SYNC_VCS_EXCLUSIONS) \
> >  		--chmod=u=rwX,go=rX --exclude .empty --exclude '*~' \
> >  		$(SKELETON_PATH)/ $(TARGET_DIR)/
> > -	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
> > -		$(TARGET_DIR_WARNING_FILE)
> > +	$(SKELETON_USR_SYMLINKS_OR_DIRS)
> >  	ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
> > -	mkdir -p $(TARGET_DIR)/usr
>  Huh, where did the mkdir go? Did you remove it because /usr is already in the
> skeleton?

Yes, it's not needed because we indeed already have it in the skeleton.
I should probably have said so in the commit log, indeed.

> >  	ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)
> > +	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
> > +		$(TARGET_DIR_WARNING_FILE)
>  And why did you move this one around?

IMHO, it makes more sense to add it last, after the skeleton has been
entirely constructed. Granted, it's mostly eye-candy, still I find it
much nicer to look at this code now than as it was before.

Regards,
Yann E. MORIN.
Mike Williams Sept. 9, 2015, 1:54 p.m. UTC | #4
Yann,

On Fri, Sep 4, 2015 at 4:17 PM, Yann E. MORIN <yann.morin.1998@free.fr> wrote:
> systemd is increasingly expecting things to live in /usr/bin, /usr/sbin
> or /usr/lib nad not in /bin, /sbin or /lib. It has inherited those
> expectations from a Fedora change:
>     https://fedoraproject.org/wiki/Features/UsrMove

I'm out on vacation, but I'll be back at work on Monday and will test
the latest revision then.

Thanks,
Mike
Mike Williams Sept. 14, 2015, 6:02 p.m. UTC | #5
Yann,

Works for me, feel free to add my:

Tested-by: Mike Williams <mike@mikebwilliams.com>
Yann E. MORIN Sept. 14, 2015, 6:19 p.m. UTC | #6
Mike, All,

On 2015-09-14 14:02 -0400, Mike Williams spake thusly:
> Works for me, feel free to add my:

Your tested-by tag will be picked up automatically when a maintainer
applies the patch.

> Tested-by: Mike Williams <mike@mikebwilliams.com>

Thanks for testing! :-)

Regards,
Yann E. MORIN.
Thomas Petazzoni Oct. 14, 2015, 9:14 p.m. UTC | #7
Dear Yann E. MORIN,

On Fri,  4 Sep 2015 22:17:32 +0200, Yann E. MORIN wrote:
> systemd is increasingly expecting things to live in /usr/bin, /usr/sbin
> or /usr/lib nad not in /bin, /sbin or /lib. It has inherited those
> expectations from a Fedora change:
>     https://fedoraproject.org/wiki/Features/UsrMove
> 
> Note however, that systemd does support /usr being on a separate
> filesystem; it just expects an initramfs to mount it before the final
> switchroot over to the actual rootfs.
> 
> But the traditional use-case for Buildroot is not to boot with an
> initramfs; although that is totally feasible, that's probably not what
> is commonly done in the vast majority of cases.
> 
> However, a lot of packages still install stuff directly into /bin,
> /sbin or /lib, which systemd may need early-on in the boot process,
> even before it may have a chance to mount /usr. Even though we can
> tell systemd, at configure-time, where it should expect programs to
> be at runtime, it does not make sense to go head-first against an
> upstream wa^Hill.
> 
> Add an option so that /bin, /sbin and /lib be symlinks to /usr/bin
> and /usr/sbin. That option is forcibly enabled when the init system
> is systemd.
> 
> Note: we need not handle /lib32 or /lib64, as they already are symlinks
> to /lib, which means they will automatically be redirected to /usr/lib,
> as /usr/lib32 and /usr/lib64 already are.
> 
> Furthermore, this means we're no longer supporting a split-usr setup, so
> the corresponding configure options have been removed as well for
> systemd and, when using a merged /usr, for eudev as well.
> 
> In Buildroot, we decided (with this patch) not to support a split-usr
> when systemd is used as an init system. This is a design decision, not
> a systemd issue. Thus the select is with BR2_INIT_SYSTEMD rather than
> with BR2_PACKAGE_SYSTEMD.
> 
> Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
> Cc: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> Cc: Arnout Vandecappelle <arnout@mind.be>
> Cc: Mike Williams <mike@mikebwilliams.com>
> Cc: Vicente Olivert Riera <Vincent.Riera@imgtec.com>
> Cc: Baruch Siach <baruch@tkos.co.il>
> 
> ---
> Changes v2 -> v3:
>   - only conditionally drop the split-usr options for eudev  (Vicente)
>   - add this missing history log  (Vicente)
>   - add a rationale on why this is the init system that selects
>     merged-usr, not the package  (Arnout).

Applied, thanks.

Thomas
diff mbox

Patch

diff --git a/package/eudev/eudev.mk b/package/eudev/eudev.mk
index 1aa74b3..a005f45 100644
--- a/package/eudev/eudev.mk
+++ b/package/eudev/eudev.mk
@@ -22,16 +22,18 @@  EUDEV_CONF_ENV += LIBS=-lrt
 EUDEV_CONF_OPTS =		\
 	--disable-manpages	\
 	--sbindir=/sbin		\
-	--with-rootlibdir=/lib	\
 	--libexecdir=/lib	\
 	--with-firmware-path=/lib/firmware	\
 	--disable-introspection			\
-	--enable-split-usr			\
 	--enable-libkmod
 
 EUDEV_DEPENDENCIES = host-gperf host-pkgconf util-linux kmod
 EUDEV_PROVIDES = udev
 
+ifeq ($(BR2_ROOTFS_MERGED_USR),)
+EUDEV_CONF_OPTS += --with-rootlibdir=/lib --enable-split-usr
+endif
+
 ifeq ($(BR2_PACKAGE_EUDEV_RULES_GEN),y)
 EUDEV_CONF_OPTS += --enable-rule_generator
 endif
diff --git a/package/skeleton/skeleton.mk b/package/skeleton/skeleton.mk
index 48e7085..920d3b4 100644
--- a/package/skeleton/skeleton.mk
+++ b/package/skeleton/skeleton.mk
@@ -19,15 +19,29 @@  else
 SKELETON_PATH = system/skeleton
 endif
 
+ifeq ($(BR2_ROOTFS_MERGED_USR),y)
+define SKELETON_USR_SYMLINKS_OR_DIRS
+	ln -snf usr/bin $(TARGET_DIR)/bin
+	ln -snf usr/sbin $(TARGET_DIR)/sbin
+	ln -snf usr/lib $(TARGET_DIR)/lib
+endef
+else
+define SKELETON_USR_SYMLINKS_OR_DIRS
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/bin
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/sbin
+	$(INSTALL) -d -m 0755 $(TARGET_DIR)/lib
+endef
+endif
+
 define SKELETON_INSTALL_TARGET_CMDS
 	rsync -a --ignore-times $(SYNC_VCS_EXCLUSIONS) \
 		--chmod=u=rwX,go=rX --exclude .empty --exclude '*~' \
 		$(SKELETON_PATH)/ $(TARGET_DIR)/
-	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
-		$(TARGET_DIR_WARNING_FILE)
+	$(SKELETON_USR_SYMLINKS_OR_DIRS)
 	ln -snf lib $(TARGET_DIR)/$(LIB_SYMLINK)
-	mkdir -p $(TARGET_DIR)/usr
 	ln -snf lib $(TARGET_DIR)/usr/$(LIB_SYMLINK)
+	$(INSTALL) -m 0644 support/misc/target-dir-warning.txt \
+		$(TARGET_DIR_WARNING_FILE)
 endef
 
 SKELETON_TARGET_GENERIC_HOSTNAME = $(call qstrip,$(BR2_TARGET_GENERIC_HOSTNAME))
diff --git a/package/systemd/systemd.mk b/package/systemd/systemd.mk
index b62fc08..59ab103 100644
--- a/package/systemd/systemd.mk
+++ b/package/systemd/systemd.mk
@@ -28,7 +28,6 @@  endif
 
 SYSTEMD_CONF_OPTS += \
 	--with-rootprefix= \
-	--with-rootlibdir=/lib \
 	--enable-static=no \
 	--disable-manpages \
 	--disable-selinux \
@@ -37,7 +36,6 @@  SYSTEMD_CONF_OPTS += \
 	--with-dbuspolicydir=/etc/dbus-1/system.d \
 	--with-dbussessionservicedir=/usr/share/dbus-1/services \
 	--with-dbussystemservicedir=/usr/share/dbus-1/system-services \
-	--enable-split-usr \
 	--disable-efi \
 	--disable-gnuefi \
 	--disable-tests \
diff --git a/system/Config.in b/system/Config.in
index fad829d..7d73e27 100644
--- a/system/Config.in
+++ b/system/Config.in
@@ -78,6 +78,10 @@  config BR2_INIT_SYSV
 	select BR2_PACKAGE_INITSCRIPTS
 	select BR2_PACKAGE_SYSVINIT
 
+# In Buildroot, we decided not to support a split-usr when systemd is
+# used as an init system. This is a design decision, not a systemd
+# issue. Thus the select is with BR2_INIT_SYSTEMD (below) rather than
+# with BR2_PACKAGE_SYSTEMD.
 config BR2_INIT_SYSTEMD
 	bool "systemd"
 	depends on BR2_PACKAGE_SYSTEMD_ARCH_SUPPORTS
@@ -88,6 +92,7 @@  config BR2_INIT_SYSTEMD
 	depends on BR2_USE_MMU
 	depends on !BR2_STATIC_LIBS
 	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_10
+	select BR2_ROOTFS_MERGED_USR
 	select BR2_PACKAGE_SYSTEMD
 
 comment 'systemd needs an (e)glibc toolchain, headers >= 3.10'
@@ -178,6 +183,18 @@  endif
 
 if BR2_ROOTFS_SKELETON_DEFAULT
 
+config BR2_ROOTFS_MERGED_USR
+	bool "Use symlinks to /usr for /bin, /sbin and /lib"
+	help
+	  If you say 'n' here, then /bin, /sbin and /lib and their
+	  counterparts in /usr will be separate directories. This
+	  is the historical UNIX way. In this case, /usr can be a
+	  filesystem on a partition separate from / .
+
+	  If you say 'y' here, then /bin, /sbin and /lib will be symlinks
+	  to their counterparts in /usr. In this case, /usr can not be a
+	  separate filesystem.
+
 config BR2_TARGET_ENABLE_ROOT_LOGIN
 	bool "Enable root login with password"
 	default y