/*********************************************************************************
* 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：
1. 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：
1. mount /dev/mmcblk0p2 /mnt
2. mount -t proc proc /mnt/proc
3. mount -t sysfs sys /mnt/sys
4. mount -o bind /dev /mnt/dev
5. chroot /mnt/
三、实际操作及数据：
[zengjf@root ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 3096336 492148 2446904 17% /
tmpfs 423848 0 423848 0% /dev/shm
tmpfs 423848 32 423816 0% /tmp
tmpfs 423848 28 423820 0% /run
[zengjf@root ~]# mount /dev/mmcblk0p2 /mnt
EXT3-fs: barriers not enabled
kjournald starting. Commit interval 5 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-0 ptys2 tty35 ttyrb
i2c-1 ptys3 tty36 ttyrc
i2c-2 ptys4 tty37 ttyrd
i2c-3 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
1 1474 517 cpuinfo mounts
10 1483 524 crypto mtd
11 1618 526 devices net
1104 1623 530 diskstats pagetypeinfo
1198 1624 539 dri partitions
1273 1630 540 driver scsi
1309 1634 591 execdomains self
1315 1637 6 fb slabinfo
1320 2 607 filesystems softirqs
1321 3 613 fs stat
1322 338 639 interrupts swaps
1361 340 641 iomem sys
1362 342 7 ioports sysrq-trigger
1363 376 8 irq sysvipc
1382 380 9 kallsyms timer_list
1394 391 apm kmsg tty
1395 4 asound kpagecount uptime
1398 414 buddyinfo kpageflags version
1407 415 bus loadavg vmallocinfo
1410 428 cmdline locks vmstat
1455 430 config.gz meminfo zoneinfo
1462 5 consoles misc
1469 516 cpu modules
[zengjf@root /]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 99150 16976 77054 18% /
devpts 3096336 492148 2446904 17% /dev/pts
tmpfs 3096336 492148 2446904 17% /dev/shm
tmpfs 99150 16976 77054 18% /tmp
df: /run: No such file or directory
/dev/mmcblk0p2 99150 16976 77054 18% /
/dev/root 3096336 492148 2446904 17% /dev
[zengjf@root /]# exit
[zengjf@root ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 3096336 492148 2446904 17% /
tmpfs 423848 0 423848 0% /dev/shm
tmpfs 423848 32 423816 0% /tmp
tmpfs 423848 28 423820 0% /run
/dev/mmcblk0p2 99150 16976 77054 18% /mnt
/dev/root 3096336 492148 2446904 17% /mnt/dev
[zengjf@root ~]#
