Boot Log

Linux version 2.6.26.8 (wolf@wpbook.local) (gcc version 4.1.2) #5 Sun Dec 21 14:47:58 PST 2008 CPU revision is: 00019064 (MIPS 4KEc) Determined physical RAM map: memory: 01000000 @ 00000000 (usable) Entering add_active_range(0, 0, 4096) 0 entries of 256 used Initrd not found or empty - disabling initrd Zone PFN ranges: Normal 0 -> 4096 Movable zone start PFN for each node early_node_map[1] active PFN ranges 0: 0 -> 4096 On node 0 totalpages: 4096 Normal zone: 32 pages used for memmap Normal zone: 0 pages reserved Normal zone: 4064 pages, LIFO batch:0 Movable zone: 0 pages used for memmap Built 1 zonelists in Zone order, mobility grouping off. Total pages: 4064 Kernel command line: console=ttyS0,9600 rootfstype=squashfs,jffs2 init=/etc/preinit Primary instruction cache 16kB, VIPT, 4-way, linesize 16 bytes. Primary data cache 16kB, 4-way, VIPT, no aliases, linesize 16 bytes PID hash table entries: 64 (order: 6, 256 bytes) console [ttyS0] enabled Dentry cache hash table entries: 2048 (order: 1, 8192 bytes) Inode-cache hash table entries: 1024 (order: 0, 4096 bytes) Memory: 13632k/16384k available (1817k kernel code, 2752k reserved, 301k data, 124k init, 0k highmem) SLUB: Genslabs=6, HWalign=32, Order=0-3, MinObjects=0, CPUs=1, Nodes=1 Calibrating delay loop... 183.50 BogoMIPS (lpj=917504) Mount-cache hash table entries: 512 net_namespace: 484 bytes NET: Registered protocol family 16 Radio config found at offset 0xf8(0x1f8) AR531x PCI init... done PCI: fixing up device 0,3,0 PCI: Failed to allocate mem resource #1:4000000@84000000 for 0000:00:00.0 PCI: Failed to allocate mem resource #1:4000000@84000000 for 0000:00:03.0 Switched to high resolution mode on CPU 0 NET: Registered protocol family 2 IP route cache hash table entries: 1024 (order: 0, 4096 bytes) TCP established hash table entries: 512 (order: 0, 4096 bytes) TCP bind hash table entries: 512 (order: -1, 2048 bytes) TCP: Hash tables configured (established 512 bind 512) TCP reno registered NET: Registered protocol family 1 ar531x: Registering GPIODEV device squashfs: version 3.0 (2006/03/15) Phillip Lougher Registering mini_fo version $Id$ JFFS2 version 2.2. (NAND) (SUMMARY) © 2001-2006 Red Hat, Inc. msgmni has been set to 26 io scheduler noop registered io scheduler deadline registered (default) gpiodev: gpio device registered with major 254 gpiodev: gpio platform device registered with access mask FFFFFFFF Serial: 8250/16550 driver $Revision: 1.90 $ 1 ports, IRQ sharing disabled serial8250: ttyS0 at MMIO 0xb1100003 (irq = 37) is a 16550A eth0: Atheros AR231x: 00:18:84:16:50:10, irq 4 ar2313_eth_mii: probed eth0: attached PHY driver [Generic PHY] (mii_bus:phy_addr=0:00) cmdlinepart partition parsing not available Searching for RedBoot partition table in spiflash at offset 0x7d0000 Searching for RedBoot partition table in spiflash at offset 0x7e0000 6 RedBoot partitions found on MTD device spiflash eth0: Configuring MAC for full duplex Creating 6 MTD partitions on "spiflash": 0x00000000-0x00030000 : "RedBoot" 0x00030000-0x00720000 : "rootfs" mtd: partition "rootfs" set to be root filesystem mtd: partition "rootfs_data" created automatically, ofs=150000, len=5D0000 0x00150000-0x00720000 : "rootfs_data" 0x00720000-0x007d0000 : "vmlinux.bin.l7" 0x007e0000-0x007ef000 : "FIS directory" 0x007ef000-0x007f0000 : "RedBoot config" 0x007f0000-0x00800000 : "boardconfig" Registered led device: gpio1 Registered led device: wlan Registered led device: gpio3 Registered led device: gpio4 Registered led device: gpio7 TCP vegas registered NET: Registered protocol family 17 802.1Q VLAN Support v1.8 Ben Greear All bugs added by David S. Miller VFS: Mounted root (squashfs filesystem) readonly. Freeing unused kernel memory: 124k freed Please be patient, while OpenWrt loads ... Algorithmics/MIPS FPU Emulator v1.5 mini_fo: using base directory: / mini_fo: using storage directory: /jffs device eth0 entered promiscuous mode br-lan: port 1(eth0) entering learning state br-lan: topology change detected, propagating br-lan: port 1(eth0) entering forwarding state PPP generic driver version 2.4.2 ip_tables: (C) 2000-2006 Netfilter Core Team br-lan: port 1(eth0) entering disabled state br-lan: port 1(eth0) entering learning state br-lan: topology change detected, propagating br-lan: port 1(eth0) entering forwarding state nf_conntrack version 0.5.0 (1024 buckets, 4096 max) wlan: trunk ath_hal: module license 'Proprietary' taints kernel. ath_hal: 2008-10-02 (AR5212, AR5312, RF5111, RF5112, RF2316, RF2317, REGOPS_FUNC, TX_DESC_SWAP, DFS, XR) ath_rate_minstrel: Minstrel automatic rate control algorithm 1.2 (trunk) ath_rate_minstrel: look around rate set to 10% ath_rate_minstrel: EWMA rolloff level set to 75% ath_rate_minstrel: max segment size in the mrr set to 6000 us wlan: mac acl policy registered ath_ahb: trunk Atheros HAL provided by OpenWrt, DD-WRT and MakSat Technologies wifi0: 11b rates: 1Mbps 2Mbps 5.5Mbps 11Mbps wifi0: 11g rates: 1Mbps 2Mbps 5.5Mbps 11Mbps 6Mbps 9Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps wifi0: turboG rates: 6Mbps 12Mbps 18Mbps 24Mbps 36Mbps 48Mbps 54Mbps wifi0: H/W encryption support: WEP AES AES_CCM TKIP ath_ahb: wifi0: Atheros 2315 WiSoC: mem=0xb0000000, irq=3 device ath0 entered promiscuous mode br-lan: port 2(ath0) entering learning state br-lan: topology change detected, propagating br-lan: port 2(ath0) entering forwarding state

When the kernel boots, it detects the presence of the root file system image (openwrt-atheros-root.squashfs) and mounts it as the root file system. The boot log also reveals that initrd, the initial Ram Disk that a Linux distribution typically mounts during the boot process, is missing. Instead, the kernel command line parameter specifies /etc/preinit as the the first process to gain control at the completion of the kernel's boot process. It also specifies a single console on device ttyS0 at 9600 baud, and the root file system's type as squashfs.

Boot Log (abridged)

Linux version 2.6.26.8 (wolf@wpbook.local) (gcc version 4.1.2) #5 Sun Dec 21 14:47:58 PST 2008
..
Initrd not found or empty - disabling initrd
..
Kernel command line: console=ttyS0,9600 rootfstype=squashfs,jffs2 init=/etc/preinit


preinit

#!/bin/sh # Copyright (C) 2006 OpenWrt.org export PATH=/bin:/sbin:/usr/bin:/usr/sbin . /etc/diag.sh failsafe_ip() { ifconfig $ifname 192.168.1.1 netmask 255.255.255.0 broadcast 192.168.1.255 up } failsafe() { [ -n "$ifname" ] && grep "$ifname" /proc/net/dev >/dev/null && { failsafe_ip netmsg 192.168.1.255 "Entering Failsafe!" telnetd -l /bin/login <> /dev/null 2>&1 } lock /tmp/.failsafe ash --login } mount proc /proc -t proc mount sysfs /sys -t sysfs size=$(awk '/MemTotal:/ {l=5242880;mt=($2*1024);print((s=mt/2)<l)&&(mt>l)?mt-l:s}' /proc/meminfo) mount tmpfs /tmp -t tmpfs -o size=$size,nosuid,nodev,mode=1777 if grep devfs /proc/filesystems > /dev/null; then mount devfs /dev -t devfs M0=/dev/pty/m0 M1=/dev/pty/m1 HOTPLUG=/sbin/hotplug-call elif [ -x /sbin/hotplug2 ]; then mount -t tmpfs tmpfs /dev -o size=512K mknod /dev/console c 5 1 /sbin/hotplug2 --coldplug --set-rules-file /etc/hotplug2-init.rules /sbin/hotplug2 --no-coldplug --persistent --set-rules-file /etc/hotplug2-init.rules & M0=/dev/ptmx M1=/dev/ptmx HOTPLUG= elif [ -x /sbin/udevd ]; then mount -n -t tmpfs -o mode=0755 udev /dev /sbin/udevd --daemon /sbin/udevtrigger /sbin/udevsettle M0=/dev/pty/ptmx M1=/dev/pty/ptmx HOTPLUG= fi mkdir -p /dev/pts /dev/shm mount devpts /dev/pts -t devpts # the shell really doesn't like having stdin/out closed # that's why we use /dev/pty/m0 and m1 as replacement # for /dev/console if there's no serial console available dd if=/dev/console of=/dev/null bs=1 count=0 >/dev/null 2>/dev/null && { M0=/dev/console M1=/dev/console } exec <$M0 >$M1 2>&0 echo "- preinit -" echo "Press CTRL-C for failsafe" trap 'FAILSAFE=true' INT trap 'FAILSAFE=true' USR1 [ -e /etc/preinit.arch ] && . /etc/preinit.arch set_state preinit echo "$HOTPLUG" > /proc/sys/kernel/hotplug eval ${FAILSAFE:+failsafe} lock -w /tmp/.failsafe if [ -z "$INITRAMFS" ]; then mount_root [ -f /sysupgrade.tgz ] && { echo "- config restore -" cd / mv sysupgrade.tgz /tmp tar xzf /tmp/sysupgrade.tgz rm -f /tmp/sysupgrade.tgz sync } echo "- init -" exec /sbin/init fi

/etc/preinit contains instructions like:
mount proc /proc -t proc
mount sysfs /sys -t sysfs
mount tmpfs /tmp -t tmpfs -o size=$size,nosuid,nodev,mode=1777
mount devpts /dev/pts -t devpts

and therefore, is responsible for mounting /proc (special-purpose filesystem), /sys, /dev (devices nodes, e.g. console), and /tmp (temporary files)

/etc/preinit also triggers the execution of /etc/preinit.arch, if present. On the FON 2100 this means that support for the reset button on AR5315+ boards is being established.
As the last statement, /etc/preinit call exec /sbin/init, which in fact is a soft link to /bin/busybox
BusyBox now performs an initialization differently from a standard System V init and launches its default initialization script (/etc/init.d/rcS), i.e. BusyBox's version of init still reads the system configuration file /etc/inittab but there is no notion of runlevels.

inittab

::sysinit:/etc/init.d/rcS S boot
::shutdown:/etc/init.d/rcS K stop
tts/0::askfirst:/bin/ash --login
ttyS0::askfirst:/bin/ash --login
tty1::askfirst:/bin/ash --login

/etc/init.d/rcS is a short script that is executing all the startup (beginning with S) or shutdown scripts (beginning with K) that are stored in the /etc/rc.ddirectory. All the scripts names end in a two-digit number and will be launched in order.


#!/bin/sh
# Copyright (C) 2006 OpenWrt.org

{
  for i in /etc/rc.d/$1*; do
    [ -x $i ] && $i $2 2>&1
  done
} | logger -s -p 6 -t '' &


All the scripts in the /etc/rc.d directory are actually symbolic links. Here are all the deployed startup scripts in a default OpenWrt distribution built for the Atheros AR231x / (MIPS 4KEc):

Launch Scripts stored in /etc/rc.d/

/etc/rc.d/S10boot -> ../init.d/boot
/etc/rc.d/S20fstab -> ../init.d/fstab
/etc/rc.d/S39usb -> ../init.d/usb
/etc/rc.d/S40network -> ../init.d/network
/etc/rc.d/S45firewall -> ../init.d/firewall
/etc/rc.d/S50cron -> ../init.d/cron
/etc/rc.d/S50dropbear -> ../init.d/dropbear
/etc/rc.d/S50httpd -> ../init.d/httpd
/etc/rc.d/S50telnet -> ../init.d/telnet
/etc/rc.d/S60dnsmasq -> ../init.d/dnsmasq
/etc/rc.d/S60led -> ../init.d/led
/etc/rc.d/S95done -> ../init.d/done
/etc/rc.d/S97watchdog -> ../init.d/watchdog
/etc/rc.d/S99sysctl -> ../init.d/sysctl


Summary

A default OpenWrt deployed on a La Fonera FON router does not use initrd, an initial Ram Disk that a Linux distribution typically mounts during the boot process, nor a standard System V init. Instead, a kernel command line console=ttyS0,9600 rootfstype=squashfs,jffs2 init=/etc/preinit is used to define /etc/preinit as the the first process to gain control at the completion of the kernel's boot process. BusyBox is launched and /etc/init.d/rcS via /etc/inittab executes all the launch scripts stored in /etc/rc.d/. /etc/inittab also launches the login shell.