I.MX6 Ubuntu core porting

/***********************************************************************
 *                      I.MX6 Ubuntu core porting
 * 说明：
 *     之前查资料查到了Ubuntu core的资料，然后一直想尝试将Ubuntu core放到
 * I.MX6中，当然也想将其放到OK335xS中，于是今天花点时间将其放入I.MX6中。
 *
 *                                     2016-4-16 深圳 南山平山村 曾剑锋
 **********************************************************************/

一、参考文档：
    . 移植ubuntu core到Arm开发板
        http://blog.csdn.net/kickxxx/article/details/15341079
    . Ubuntu 14.04 for i.MX6
        https://support.bluetechnix.at/wiki/Ubuntu_14.04_for_i.MX6

二、download:
    1. https://developer.ubuntu.com/en/snappy/
    2. http://cdimage.ubuntu.com/ubuntu-base/releases/12.04/release/
    3. http://mirror1.ku.ac.th/ubuntu-cdimages/ubuntu-core/
三、解压打包：
    tar zxvf ubuntu-core-12.04.-core-armhf.tar.gz -C rootfs/
    cd rootfs
    tar jcvf rootfs.tar.bz2 *
    mv rootfs.tar.bz2 ..
    cd ..
    cp rootfs.tar.bz2 /mnt/hgfs/Desktop/

四、error
    . error1：
        . 内核打印信息在如下位置停止了：
            ......
            EXT3-fs (mmcblk0p1): warning: checktime reached, running e2fsck is recommended
            kjournald starting.  Commit interval  seconds
            EXT3-fs (mmcblk0p1): using internal journal
            EXT3-fs (mmcblk0p1): mounted filesystem with writeback data mode
            VFS: Mounted root (ext3 filesystem) on device :.
            Freeing init memory: 208K
            init: Unable to mount /dev filesystem: No such device
        . 问题原因：
            debug的终端口没有打开，需要另外配置console。
        . cat /etc/init/ttymxc.conf
            # console - getty
            #
            # This service maintains a getty on console from the point the system is
            # started until it is shut down again.

            start on stopped rc RUNLEVEL=[] and (
                        not-container or
                        container CONTAINER=lxc or
                        container CONTAINER=lxc-libvirt)

            stop on runlevel [!]

            respawn
            exec /sbin/getty -L  ttymxc0 vt102
        . cat /etc/init.d/rc.local
            ......
            start ttymxc0
            ......
    . error2：
        . root用户需要密码，去掉该功能；
        . cat /etc/passwd
            root::::root:/root:/bin/bash
            daemon:x:::daemon:/usr/sbin:/bin/sh
            bin:x:::bin:/bin:/bin/sh
            sys:x:::sys:/dev:/bin/sh
            sync:x:::sync:/bin:/bin/sync
            games:x:::games:/usr/games:/bin/sh
            man:x:::man:/var/cache/man:/bin/sh
            lp:x:::lp:/var/spool/lpd:/bin/sh
            mail:x:::mail:/var/mail:/bin/sh
            news:x:::news:/var/spool/news:/bin/sh
            uucp:x:::uucp:/var/spool/uucp:/bin/sh
            proxy:x:::proxy:/bin:/bin/sh
            www-data:x:::www-data:/var/www:/bin/sh
            backup:x:::backup:/var/backups:/bin/sh
            list:x:::Mailing List Manager:/var/list:/bin/sh
            irc:x:::ircd:/var/run/ircd:/bin/sh
            gnats:x:::Gnats Bug-Reporting System (admin):/var/lib/gnats:/bin/sh
            nobody:x:::nobody:/nonexistent:/bin/sh
            libuuid:x::::/var/lib/libuuid:/bin/sh
    . error3：
        . 第一次运行现象：
            ......
            EXT3-fs: barriers not enabled
            kjournald starting.  Commit interval  seconds
            EXT3-fs (mmcblk0p1): warning: checktime reached, running e2fsck is recommended
            EXT3-fs (mmcblk0p1): using internal journal
            EXT3-fs (mmcblk0p1): mounted filesystem with writeback data mode
            VFS: Mounted root (ext3 filesystem) on device :.
            Freeing init memory: 208K
            init: Unable to mount /dev filesystem: No such device
            start: Unknown job: ttymxc0                                                     

            Ubuntu 12.04. LTS localhost.localdomain ttymxc0                                

            localhost login:
        . 第二次运行现象：
            ......
            EXT3-fs: barriers not enabled
            kjournald starting.  Commit interval  seconds
            EXT3-fs (mmcblk0p1): warning: checktime reached, running e2fsck is recommended
            EXT3-fs (mmcblk0p1): using internal journal
            EXT3-fs (mmcblk0p1): recovery complete
            EXT3-fs (mmcblk0p1): mounted filesystem with writeback data mode
            VFS: Mounted root (ext3 filesystem) on device :.
            Freeing init memory: 208K                                                       

            Ubuntu 12.04. LTS localhost.localdomain ttymxc0                                

            localhost login:
        . 目前没有花时间来分析两次现象不同的原因。