[Buildroot] [PATCH 23/24 v2] system: make systemd work on a read-only rootfs

[Yann E. MORIN]

Romain, All,

On 2016-07-03 14:54 +0200, Romain Naour spake thusly:
> Le 22/06/2016 à 21:07, Yann E. MORIN a écrit :
> > When the rootfs is readonly, systemd will expect /var to be writable.
> > Because we do not really have a R/W filesystem to mount on /var, we make
> > it a tmpfs, and use the systemd-tmpfiles feautre to populate it with
> s/feautre/feature/
[--SNIP--]
> Other than small typos highlighted by my mail client ;-)

Typoes fixed, thanks!

Regards,
Yann E. MORIN.

> Reviewed-by: Romain Naour <romain.naour at gmail.com>
> 
> Best regards,
> Romain
> 
> 
> > ---
> > Note: I haven't seen any symlinks installed in the factory so far, but I
> > haven't build a lot of packages yet... So, I'm not sure what to do with
> > the symlinks, especially when a package install relative symlinks...
> > ---
> >  package/skeleton-systemd/skeleton-systemd.mk | 51 ++++++++++++++++++++++++++--
> >  system/Config.in                             |  1 -
> >  2 files changed, 49 insertions(+), 3 deletions(-)
> > 
> > diff --git a/package/skeleton-systemd/skeleton-systemd.mk b/package/skeleton-systemd/skeleton-systemd.mk
> > index b45bbde..c7c2e26 100644
> > --- a/package/skeleton-systemd/skeleton-systemd.mk
> > +++ b/package/skeleton-systemd/skeleton-systemd.mk
> > @@ -36,12 +36,59 @@ ifeq ($(SKELETON_SYSTEM_LOCALTIME),)
> >  SKELETON_SYSTEM_LOCALTIME = Etc/UTC
> >  endif
> >  
> > +ifeq ($(BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW),y)
> > +
> > +define SKELETON_SYSTEMD_ROOT_RW
> > +	echo "/dev/root / auto rw 0 1" >$(TARGET_DIR)/etc/fstab
> > +	mkdir -p $(TARGET_DIR)/var
> > +endef
> > +
> > +else
> > +
> > +# On a R/O rootfs, /var is a tmpfs filesystem. So, at build time, we
> > +# redirect /var to the "factory settings" location. Just before the
> > +# filesystem gets created, the /var symlink will be replaced with
> > +# a real (but empty) directory, and the "factory files" will be copied
> > +# back there by the tmpfiles.d mechanism.
> > +define SKELETON_SYSTEMD_ROOT_RO
> > +	mkdir -p $(TARGET_DIR)/etc/systemd/tmpfiles.d
> > +	mkdir -p $(TARGET_DIR)/usr/share/factory
> > +	ln -s usr/share/factory $(TARGET_DIR)/var
> > +	echo "/dev/root / auto ro 0 1" >$(TARGET_DIR)/etc/fstab
> > +	echo "tmpfs /var tmpfs mode=1777 0 0" >>$(TARGET_DIR)/etc/fstab
> > +endef
> > +
> > +define SKELETON_SYSTEMD_VAR_PRE_FS
> > +	rm -f $(TARGET_DIR)/var
> > +	mkdir $(TARGET_DIR)/var
> > +	for i in $(TARGET_DIR)/usr/share/factory/*; do \
> > +		j="$${i##*/}"; \
> > +		if [ -L "$${i}" ]; then \
> > +			printf "L+! /var/%s - - - - %s\n" \
> > +				"$${j}" "../usr/share/factory/$${j}" \
> > +			|| exit 1; \
> > +		else \
> > +			printf "C! /var/%s - - - -\n" "$${j}" \
> > +			|| exit 1; \
> > +		fi; \
> > +	done >$(TARGET_DIR)/etc/systemd/tmpfiles.d/var-factory.conf
> > +endef
> > +SKELETON_SYSTEMD_FS_PRE_CMD_HOOKS += SKELETON_SYSTEMD_VAR_PRE_FS
> > +
> > +define SKELETON_SYSTEMD_VAR_POST_FS
> > +	rm -rf $(TARGET_DIR)/var
> > +	ln -s usr/share/factory $(TARGET_DIR)/var
> > +endef
> > +SKELETON_SYSTEMD_FS_POST_CMD_HOOKS += SKELETON_SYSTEMD_VAR_POST_FS
> > +
> > +endif
> > +
> >  define SKELETON_SYSTEMD_INSTALL_TARGET_CMDS
> >  	mkdir -p $(TARGET_DIR)/etc
> >  	mkdir -p $(TARGET_DIR)/home
> >  	mkdir -p $(TARGET_DIR)/srv
> > -	mkdir -p $(TARGET_DIR)/var
> > -	echo "/dev/root / auto rw 0 1" >$(TARGET_DIR)/etc/fstab
> > +	$(SKELETON_SYSTEMD_ROOT_RO)
> > +	$(SKELETON_SYSTEMD_ROOT_RW)
> >  	ln -sf ../usr/share/zoneinfo/$(SKELETON_SYSTEMD_LOCALTIME) \
> >  		$(TARGET_DIR)/etc/localtime
> >  	$(SKELETON_SYSTEMD_RSYNC_NETWORK)
> > diff --git a/system/Config.in b/system/Config.in
> > index 07af2e0..32d6542 100644
> > --- a/system/Config.in
> > +++ b/system/Config.in
> > @@ -129,7 +129,6 @@ config BR2_INIT_SYSTEMD
> >  	depends on BR2_TOOLCHAIN_HEADERS_AT_LEAST_3_10
> >  	select BR2_ROOTFS_MERGED_USR
> >  	select BR2_PACKAGE_SYSTEMD
> > -	select BR2_TARGET_GENERIC_REMOUNT_ROOTFS_RW
> >  	select BR2_TARGET_TZ_INFO
> >  
> >  comment "systemd needs (e)glibc toolchain, headers >= 3.10"
> > 
> 

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