/*********************************************************************************
* Linux chroot 并使用之前系统设备节点
* 说明：
* 直接使用chroot结果/dev下没有设备，所有有些东西需要提前挂载，在进入chroot。
*
* 2016-12-30 深圳 南山平山村 曾剑锋
********************************************************************************/ 一、参考文档：
. mount dev, proc, sys in a chroot environment?
http://superuser.com/questions/165116/mount-dev-proc-sys-in-a-chroot-environment 二、主要Linux Shell命令：
. mount /dev/mmcblk0p2 /mnt
. mount -t proc proc /mnt/proc
. mount -t sysfs sys /mnt/sys
. mount -o bind /dev /mnt/dev
. chroot /mnt/ 三、实际操作及数据：
[zengjf@root ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root % /
tmpfs % /dev/shm
tmpfs % /tmp
tmpfs % /run
[zengjf@root ~]# mount /dev/mmcblk0p2 /mnt
EXT3-fs: barriers not enabled
kjournald starting. Commit interval seconds
EXT3-fs (mmcblk0p2): warning: checktime reached, running e2fsck is recommended
EXT3-fs (mmcblk0p2): using internal journal
EXT3-fs (mmcblk0p2): recovery complete
EXT3-fs (mmcblk0p2): mounted filesystem with writeback data mode
[zengjf@root ~]# mount -t proc proc /mnt/proc
[zengjf@root ~]# mount -t sysfs sys /mnt/sys
[zengjf@root ~]# mount -o bind /dev /mnt/dev
[zengjf@root ~]# chroot /mnt/ BusyBox v1.20.2 () built-in shell (ash)
Enter 'help' for a list of built-in commands. [zengjf@root /]# ls /dev/
alarm ptyr8 tty26 ttyr1
apm_bios ptyr9 tty27 ttyr2
buzzer ptyra tty28 ttyr3
console ptyrb tty29 ttyr4
cpu_dma_latency ptyrc tty3 ttyr5
fb0 ptyrd tty30 ttyr6
fb1 ptyre tty31 ttyr7
fb2 ptyrf tty32 ttyr8
full ptys0 tty33 ttyr9
galcore ptys1 tty34 ttyra
i2c- ptys2 tty35 ttyrb
i2c- ptys3 tty36 ttyrc
i2c- ptys4 tty37 ttyrd
i2c- ptys5 tty38 ttyre
input ptys6 tty39 ttyrf
kmem ptys7 tty4 ttys0
kmsg ptys8 tty40 ttys1
log ptys9 tty41 ttys2
mem ptyt2 tty5 ttysb
mmcblk0 ptyt3 tty50 ttysc
mmcblk0boot0 ptyt4 tty51 ttysd
mmcblk0boot1 ptyt5 tty52 ttyse
mmcblk0p1 ptyt6 tty53 ttysf
mmcblk0p2 ptyt7 tty54 ttyt0
mx6check ptyt8 tty55 ttyt1
mxc_asrc ptyt9 tty56 ttyt2
mxc_ipu ptyta tty57 ttyt3
mxc_vpu ptytb tty58 ttyt4
mxs_viim ptytc tty59 ttyt5
network_latency ptytd tty6 ttyt6
network_throughput ptyte tty60 ttyt7
null ptytf tty61 ttyt8
...
[zengjf@root /]# ls sys
block class devices fs kernel power
bus dev firmware fsl_otp module
[zengjf@root /]# ls proc
cpuinfo mounts
crypto mtd
devices net
diskstats pagetypeinfo
dri partitions
driver scsi
execdomains self
fb slabinfo
filesystems softirqs
fs stat
interrupts swaps
iomem sys
ioports sysrq-trigger
irq sysvipc
kallsyms timer_list
apm kmsg tty
asound kpagecount uptime
buddyinfo kpageflags version
bus loadavg vmallocinfo
cmdline locks vmstat
config.gz meminfo zoneinfo
consoles misc
cpu modules
[zengjf@root /]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root % /
devpts % /dev/pts
tmpfs % /dev/shm
tmpfs % /tmp
df: /run: No such file or directory
/dev/mmcblk0p2 % /
/dev/root % /dev
[zengjf@root /]# exit
[zengjf@root ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root % /
tmpfs % /dev/shm
tmpfs % /tmp
tmpfs % /run
/dev/mmcblk0p2 % /mnt
/dev/root % /mnt/dev
[zengjf@root ~]#