poky-tiny: Add tiny-init mechanism for poky-tiny distro

Provide a basic functional init mechanism for poky-tiny. This defines a new "tiny" DISTRO_FEATURE in poky-tiny.conf, updates the busybox config based on this DISTRO_FEATURE, and creates a new tiny-init recipe which is made the default VIRTUAL-RUNTIME_init_manager for poky-tiny.

The busybox changes are for oe-core to avoide a bbappend in meta-yocto. That one patch is CC'd to oe-core.

The following changes since commit 7f017cab0b3e4d5a4fc356eccd8eb8429b0531d0:

connman: bump PR and add some comments (2012-06-13 13:11:23 +0100)

are available in the git repository at:
git://git.pokylinux.org/poky-contrib dvhart/tiny
http://git.pokylinux.org/cgit.cgi/poky-contrib/log/?h=dvhart/tiny

Darren Hart (3):
poky-tiny: Define the "tiny" DISTRO_FEATURE
busybox: Add setsid and cttyhack for tiny DISTRO_FEATURE
tiny-init: Basic init mechanism for poky-tiny

 meta-yocto/conf/distro/poky-tiny.conf              |    8 ++----
 meta-yocto/recipes-core/tiny-init/files/init       |   21 ++++++++++++++++
 .../recipes-core/tiny-init/files/rc.local.sample   |   23 +++++++++++++++++
 meta-yocto/recipes-core/tiny-init/tiny-init.bb     |   26 ++++++++++++++++++++
 meta/recipes-core/busybox/busybox.inc              |    2 +
 5 files changed, 75 insertions(+), 5 deletions(-)
 create mode 100644 meta-yocto/recipes-core/tiny-init/files/init
 create mode 100644 meta-yocto/recipes-core/tiny-init/files/rc.local.sample
 create mode 100644 meta-yocto/recipes-core/tiny-init/tiny-init.bb

1.7.5.4

Enable recipes such as busybox to modify their configuration based on a DISTRO_FEATURE for tiny distributions.

---
 meta-yocto/conf/distro/poky-tiny.conf |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

index a34c7dc..d6295f7 100644
@@ -31,9 +31,6 @@
 require conf/distro/poky.conf
 DISTRO = "poky-tiny"
 
-# FIXME: consider adding a new "tiny" feature
-#DISTRO_FEATURES_append = " tiny"
-
 # Distro config is evaluated after the machine config, so we have to explicitly
 # set the kernel provider to override a machine config.
 PREFERRED_PROVIDER_virtual/kernel = "linux-yocto-tiny"

@@ -84,7 +81,8 @@ DISTRO_FEATURES_USB = "usbhost"
 #DISTRO_FEATURES_USBGADGET = "usbgadget"
 #DISTRO_FEATURES_WIFI = "wifi"
 
-DISTRO_FEATURES = "${DISTRO_FEATURES_TINY} \
+DISTRO_FEATURES = "tiny \
+                   ${DISTRO_FEATURES_TINY} \
                    ${DISTRO_FEATURES_NET} \
                    ${DISTRO_FEATURES_USB} \
                    ${DISTRO_FEATURES_USBGADGET} \

1.7.5.4

When building very small systems, it can be useful to spawn a shell from a simple init script, rather than a full System V Init process. This requires the shell be the session leader and be able to open the controlling terminal if it is to have job control.

Enable CONFIG_CTTYHACK and CONFIG_SETSID to enable this for distros defining the "tiny" DISTRO_FEATURE.

---
 meta/recipes-core/busybox/busybox.inc |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

index 5b83d32..d07ba7e 100644
@@ -57,6 +57,8 @@ def features_to_busybox_settings(d):
 	busybox_cfg('nls',  distro_features, 'CONFIG_LOCALE_SUPPORT', cnf, rem)
 	busybox_cfg('ipv4', distro_features, 'CONFIG_FEATURE_IFUPDOWN_IPV4', cnf, rem)
 	busybox_cfg('ipv6', distro_features, 'CONFIG_FEATURE_IFUPDOWN_IPV6', cnf, rem)
+	busybox_cfg('tiny', distro_features, 'CONFIG_SETSID', cnf, rem)
+	busybox_cfg('tiny', distro_features, 'CONFIG_CTTYHACK', cnf, rem)
 	return "\n".join(cnf), "\n".join(rem)
 
 # X, Y = ${@features_to_uclibc_settings(d)}

1.7.5.4

Note that this is a part of a larger series. The other patches are against meta-yocto, but the busybox change seemed more appropriate here than in a bbappend in meta-yocto.

At some point poky-tiny may need to come into oe-core, until then...

Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

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why do you think so. micro is also a distro with similar goals lives outside of OE-Core infact any distros live outside oe-core -----BEGIN PGP SIGNATURE-----
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Note I'm not arguing for it one way or the other. I could see people wanting it to come in with linux-yocto-tiny already in oe-core. Or, it might make more sense to move linux-yocto-tiny to meta-yocto and just keep it all contained in meta-yocto. That's fine with me too.

- --
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

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Enabling cttyhack and setsid could be a good thing in general (thinking of initramfs kind of images) so I would propose to enable it by default
and not introduce another distro knob here. How much does busybox code size grow which these two features turned on.?

otherwise second best thing is to keep it in poky-tiny distro layer which wants to set the policy
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So this struck me as strange, but I did it twice to make sure I didn't mess something up:

BEFORE
- -rwxr-xr-x 1 dvhart dvhart 2799417 2012-06-15 15:06 busybox
- -rwxr-xr-x 1 dvhart dvhart 547872 2012-06-15 15:06 busybox_stripped

AFTER (w/ SETSID and CTTYHACK)
- -rwxr-xr-x 1 dvhart dvhart 2805195 2012-06-15 14:45 busybox
- -rwxr-xr-x 1 dvhart dvhart 547872 2012-06-15 15:05 busybox_stripped

DELTA

         busybox: 5778

busybox_stripped: 0

The difference is <6k for the unstripped binary, and 0 bytes for the stripped binary. It must have something to do with the way busybox builds and enables features. The above was using my host strip command. I also tried building the rootfs with and without these features and comparing the cross-stripped binaries in the rootfs, delta is also 0 bytes.

So the cost is "negligible" and there is a clear advantage to having these two options enabled. I'll resend with a two line change to the defconfig to enable them.

- --
Darren

- --
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

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Sorry, I hit the menuconfig/sstate bug. There is a 2560 byte difference for including these two features. Seems reasonable to me. A new patch has been sent to the list.

- --
Darren

- --
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

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The idea is to avoid having to bbappend busybox and other recipes basically. I can see how "tiny" is different than "ipv4" as it isn't explicit it what it enables, making it a "grab-bag" as you put it.

I could come up with a term that describes systems without complex init systems that need to be able to setup their own shells easily.

Another approach would be to just consider these two features and decide if they shouldn't just be part of the oe-core busybox defconfig anyway. I don't see why setsid shouldn't be. I can see arguments against cttyhack (as it is a hack), but I wouldn't think either should be a huge deal to just include. I thought the DISTRO_FEATURE was a reasonable compromise between that and having to maintain a bbappend outside of oe-core.

How would you feel about just including these two features in the defconfig then?

Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel

Well, you don't need to maintain a .bbappend as such: you can just provide your own, completely custom config file for busybox. That's what micro does, what shr does (I think), and what I would suggest that most DISTROs with non-trivial configuration requirements should probably do.

I think most folks do actually use a .bbappend to fiddle FILESPATH in order to get the configuration file picked up, but I'm fairly sure you could do this with a bit of suitable magic in your distro config file and avoid the .bbappend altogether.

Not massively enthusiastic, simply because the logical conclusion of that approach is that we end up with basically everything in busybox turned on. If we're going to go along that path then I think I would prefer us to be up-front about it and just make the oe-core default configuration for busybox be a "maximum features enabled" one.

p.

Currently poky-tiny images will boot and run /bin/sh, which results in error messages to the console about being unable to open the tty and job control being disabled.

The shell must be session leader to open the tty, and the tty must not be /dev/console (it should be a vt or a physical tty like ttyS0), the tty is required for job control (handling signals, etc.).

The goals of poky-tiny are to be an initial starting point from which to build a distribution that does what you want, and NOTHING more.

This patch results in a system that boots with the virtual filesystems mounted, the local network interface up, and a shell with job control running, and a hook (/etc/rc.local) for easy customization. Nothing else.

Thanks to Tim Bird for his suggestion to include support for rc.local by default.

---
 meta-yocto/conf/distro/poky-tiny.conf              |    2 +-
 meta-yocto/recipes-core/tiny-init/files/init       |   21 ++++++++++++++++
 .../recipes-core/tiny-init/files/rc.local.sample   |   23 +++++++++++++++++
 meta-yocto/recipes-core/tiny-init/tiny-init.bb     |   26 ++++++++++++++++++++
 4 files changed, 71 insertions(+), 1 deletions(-)
 create mode 100644 meta-yocto/recipes-core/tiny-init/files/init
 create mode 100644 meta-yocto/recipes-core/tiny-init/files/rc.local.sample
 create mode 100644 meta-yocto/recipes-core/tiny-init/tiny-init.bb

index d6295f7..541e194 100644
@@ -93,7 +93,7 @@ DISTRO_FEATURES = "tiny \
 # Use tmpdevfs and the busybox runtime services
 VIRTUAL-RUNTIME_dev_manager = ""
 VIRTUAL-RUNTIME_login_manager = ""
-VIRTUAL-RUNTIME_init_manager = ""
+VIRTUAL-RUNTIME_init_manager = "tiny-init"
 VIRTUAL-RUNTIME_keymaps = ""
 
 # FIXME: Consider adding "modules" to MACHINE_FEATURES and using that in

new file mode 100644
index 0000000..bf2817d
@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# Mount the Linux kernel virtual filesystems
+mount none -t proc /proc
+mount none -t sysfs /sys
+mkdir /dev/pts
+mount none -t devpts /dev/pts
+
+ifup lo
+
+# Allow for distro or local customizations
+if [ -f /etc/rc.local ] ; then
+	source /etc/rc.local
+fi
+
+# Become session leader and try to find a real tty (e.g. ttyS0)
+while true; do
+	setsid cttyhack sh
+	echo "Console sh exited with $?, respawning..."
+	sleep 1
+done

new file mode 100644
index 0000000..d9e198a
@@ -0,0 +1,23 @@
+#!/bin/sh
+
+# Start services and customize the boot process here.
+echo "Running /etc/rc.local..."
+
+# Use init scripts included with packages such as dropbear
+#/etc/init.d/dropbear start
+
+# Spawn a getty manually
+#setsid /sbin/getty 115200 ttyS2
+
+# Print a banner
+#echo "You are running a poky-tiny image brought to you by the Yocto Project."
+
+# Setup a debugging environment
+#mkdir /debugfs
+#mount none -t debugfs /debugfs
+
+# Load modules (note: linux-yocto-tiny does not have module support by default)
+#modprobe yourdriver
+
+# DO NOT run any long running tasks or loops as these will delay
+# the /init script and the console shell.

new file mode 100644
index 0000000..1cf46ed
@@ -0,0 +1,26 @@
+SUMMARY = "Poky-tiny init"
+DESCRIPTION = "Basic init system for poky-tiny"
+LICENSE = "MIT"
+LIC_FILES_CHKSUM = "file://${COREBASE}/meta/COPYING.MIT;md5=3da9cfbcb788c80a0384361b4de20420"
+
+PR = "r0"
+
+SRC_URI = "file://init \
+	   file://rc.local.sample \
+	  "
+
+do_configure() {
+	:
+}
+
+do_compile() {
+	:
+}
+
+do_install() {
+	install -d ${D}${sysconfdir}
+	install -m 0755 ${WORKDIR}/init ${D}
+	install -m 0755 ${WORKDIR}/rc.local.sample ${D}${sysconfdir}
+}
+
+FILES_${PN} = "/init ${sysconfdir}/rc.local.sample"

1.7.5.4