2011-09-27

• 為何 rock 要把 bridge.ko 加入 /usr/bin/mkpxeinitrd-net 呢？答案很明顯是跟 brctl 有關！

  root@debian:~# lsmod > before
  root@debian:~# brctl addbr br0
  root@debian:~# lsmod > after
  root@debian:~# diff before after 
  1a2,3
  > bridge                 39662  0 
  > stp                     1440  1 bridge
  

• rock 把執行 /bin/start_xen_bridge.sh 需要用的指令都補進 initrd 裡：brctl ip egrep awk gawk seq fgrep dirname expr bash
• 可是他卻漏了 mount umount mount.nfs umount.nfs
• 至於 netloop.ko 是 xen_brdige.sh 中會用到的，在 KVM 的 case 中並不會用到。

  /usr/bin/mkpxeinitrd-net

  @@ -37 +37 @@
   # uncompress the compress kernel module. This is special for Mandriva case. It uses compressed kernel module, e.g. pcnet32.ko.gz. Before we used modprobe from busybox, we have to uncompress that. Now the modprobe program is from the OS (See variable include_bin_prog_from_server), so we should allow this type of kernel modules.
   use_compressed_kernel_module="yes"
   # Some required bin programs to be included in the PXE initrd, which are not provided by busybox or the one provided by busybox does not support the function we want. E.g. sleep (we need "sleep 0.1", while sleep from busybox does not support 0.1 secs).
  -include_bin_prog_from_server="sleep lspci insmod modprobe rmmod lsmod pkill strings mount umount mount.nfs umount.nfs"
  +# drbl-virt add
  +include_bin_prog_from_server='sleep lspci insmod modprobe rmmod lsmod pkill strings brctl ip egrep awk gawk seq fgrep dirname expr bash'
   
   # No need to use sudo if we are root
   if [ $UID -eq 0 ]; then
  @@ -303 +304 @@
        cp -a --parents $i $initrd/lib/modules/$kernel_ver/
      done
   
  +# drbl-virt add
  +cp -a --parents kernel/net/bridge/bridge.ko $initrd/lib/modules/$kernel_ver/
  +cp -a --parents kernel/drivers/xen/netback/netloop.ko $initrd/lib/modules/$kernel_ver/
      # Deal with firmwares!
      # The following is borrowed from Debian's /usr/share/initramfs-tools/hook-functions
      if [ "$copy_all_firmwares" = "yes" ]; then

• rock 的 init 切入點蠻特殊的，我原本是把切換成 br0 的程序加在 udhcpc 之前，試圖讓 br0 去取得 IP 位址。可是卻會出現 /sbin/init 第 175 行錯誤的問題。

  150 $echo "Bringing up loopback interface"
  151 ifconfig lo 127.0.0.1 up
  152 route add -net 127.0.0.0 netmask 255.0.0.0 lo
  153 ### 加在這裡
  +   brctl addbr br0
  +   brctl addif br0 eth0
  +   ifconfig br0 0.0.0.0   ### 在 initrd.img 中要用這種方式才能啟動 br0
  +   ifconfig eth0 0.0.0.0  
  +   sleep 0.1
  

• 若是在 udhcpc 已經用 eth0 取得 IP 之後，才去把 eth0 暫停，新增 br0，再將 eth0 加入 br0，就能正常掛載 NFS 當 ROOTFS。這真的是需要一些觀念啊～

  /usr/lib/mkpxeinitrd-net/initrd-skel/linuxrc-or-init

  @@ -244 +244 @@
     done
   done
   
  +# drbl-virt add
  +bash /bin/start_xen_bridge.sh
   # clean the tag file
   [ -f "/dev/sname" ] && rm -f /dev/sname

• start_xen_bridge.sh 其實有點小複雜，會先去判斷網卡個數，然後透過 /bin/network-bridge 的 netdev 參數來指定網卡。

  # cat /usr/lib/mkpxeinitrd-net/initrd-skel/bin/start_xen_bridge.sh
  #!/bin/bash
  # drbl-virt add
  NICs=$(/sbin/ifconfig | grep eth | awk '{print $1}')
  declare -i NICs_nu=$(echo $NICs |wc -w)
  NIC=""
  
  if [ $NICs_nu -lt 1  ]; then
      for (( i=0 ; i<$NICs_nu ; i++ ))
      do
          NIC_IP=$(ifconfig eth${i} | grep "inet addr" | sed 's/inet addr://g' | sed 's/Bcast.*$//g' | sed 's/^[ ]*//')
          if [ -n $NIC_IP ]; then
              NIC="eth${i}"
              break
          fi
      done
  else
      NIC=$NICS
  fi
  
  bash /bin/network-bridge start netdev=$NIC
  

• 關於