read-only rootfs support

From: Chen Qi <[email protected]>

The series of patches add support to read-only rootfs.

The main idea is to use symbolic links to create the illuion that some directories are writable in case of a read-only rootfs.

This set of patches have been tested on minimal images with and without 'read-only-rootfs' image feature enabled. Everything is OK.

For sato images, everything is the same as before if 'read-only-rootfs' is not enabled. With 'read-only-rootfs' enabled, sato image could work if graphic interface is diabled. When all postinstall problems are resolved, sato image should work well (maybe with some small changes in volatiles-readonly-sato conf file).

Changes for Version 4:
1) Improve the commit messages to be clearer.
2) Use 'sed -i' to replace 'sed' and 'mv' operations to cut down the exec overhead.

Changes for Version 5:
Fix the problem of failing to build the live images

Changes for Version 6:
1) Let the image recipes provide the corresponding conf files for read-only rootfs. The config files are closely related to the image types, so it's more reasonable to let these image recipes provide the config files.
2) Support customized conf files for customized images.

Changes for Version 7:
1) Separate read-only-rootfs specific conf files from image recipes. Create recipes for them and let image recipes depend on the them.
2) 'choose_volatiel_conf' is no more need, thus removed.

Changes for Version 8:
Rebase these patches against the latest master branch (after the systemd integration)

The following changes since commit 37e025f6f9c410005e0f1dee0767e38eaec01cbd:

bitbake: hob: Hob should display warnings generated during parsing (2013-01-21 19:05:31 +0000)

are available in the git repository at:

git://git.pokylinux.org/poky-contrib ChenQi/readonly-rootfs
http://git.pokylinux.org/cgit.cgi/poky-contrib/log/?h=ChenQi/readonly-rootfs

Chen Qi (6):
sysvinit: add ROOTFS_READ_ONLY variable to rcS-default image.bbclass: add a hook funtion to support readonly rootfs core-image.bbclass: support read-only rootfs
initscripts: support read-only rootfs
volatile-conf-minimal: add recipe
volatile-conf-sato: add recipe

 meta/classes/core-image.bbclass                    |    4 +
 meta/classes/image.bbclass                         |   18 ++
 meta/recipes-core/images/core-image-minimal.bb     |    3 +
 .../initscripts/initscripts-1.0/bootmisc.sh        |    9 +-
 .../initscripts-1.0/populate-volatile.sh           |  281 ++++++++++----------
 .../initscripts/initscripts-1.0/volatiles          |    1 +
 meta/recipes-core/initscripts/initscripts_1.0.bb   |    2 +-
 .../files/volatiles-readonly-minimal               |    8 +
 .../volatile-conf-minimal_1.0.bb                   |   15 ++
 meta/recipes-core/sysvinit/sysvinit/rcS-default    |    4 +
 meta/recipes-core/sysvinit/sysvinit_2.88dsf.bb     |    2 +-
 meta/recipes-sato/images/core-image-sato.bb        |    3 +
 .../files/volatiles-readonly-sato                  |   14 +
 .../volatile-conf-sato_1.0.bb                      |   15 ++
 14 files changed, 226 insertions(+), 153 deletions(-)
 create mode 100644 meta/recipes-core/readonly-volatile-conf/files/volatiles-readonly-minimal
 create mode 100644 meta/recipes-core/readonly-volatile-conf/volatile-conf-minimal_1.0.bb
 create mode 100644 meta/recipes-sato/readonly-volatile-conf/files/volatiles-readonly-sato
 create mode 100644 meta/recipes-sato/readonly-volatile-conf/volatile-conf-sato_1.0.bb

1.7.9.5