uClibc和BusyBox已经编译好了，在把它们加入固件之前最好先测试一下。测试方法是建立一个模拟的根文件系统，通过chroot命令来建立一个新的执行环境，在这个环境下所执行的命令以及动态连接库都来自于这个模拟的根文件系统。
模拟根文件系统的制作方法（在PC上执行）：
准备一个U盘或移动硬盘，格式化成ext3文件系统。
假设编译好的uClibc和BusyBox分别放在/home/user/dist/uclibc和/home/user/dist/busybox目录下，U盘挂载在/media/disk下。
执行下列的命令来制作测试U盘：
1 $ cp -a /home/user/dist/uclibc/lib /media/disk
2 $ cp -a /home/user/dist/busybox/* /media/disk
3 $ cd /media/disk
4 $ mkdir proc dev var tmp
制作好的U盘将有如下的文件列表：
1 $ ls -lR
2 .:
3 total 32
4 drwxr-xr-x 2 user users 4096 2010-03-18 13:47 bin
5 drwxr-xr-x 2 user users 4096 2010-03-18 22:39 dev
6 drwxr-xr-x 2 user users 4096 2010-03-18 13:47 lib
7 drwxr-xr-x 2 user users 4096 2010-03-18 22:39 proc
8 drwxr-xr-x 2 user users 4096 2010-03-18 22:09 sbin
9 drwxr-xr-x 2 user users 4096 2010-03-18 22:39 tmp
10 drwxr-xr-x 4 user users 4096 2010-03-18 22:08 usr
11 drwxr-xr-x 2 user users 4096 2010-03-18 22:39 var
12
13 ./bin:
14 total 720
15 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 ash -> busybox
16 -rwxr-xr-x 1 user users 732460 2010-03-18 13:47 busybox
17 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 cat -> busybox
18 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 chmod -> busybox
19 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 chown -> busybox
20 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 cp -> busybox
21 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 date -> busybox
22 略去若干行
23 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 umount -> busybox
24 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 uname -> busybox
25 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 usleep -> busybox
26 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 vi -> busybox
27 lrwxrwxrwx 1 user users 7 2010-03-18 22:07 zcat -> busybox
28
29 ./dev:
30 total 0
31
32 ./lib:
33 total 720
34 -rwxr-xr-x 1 user users 21232 2010-03-18 13:47 ld-uClibc-0.9.28.so
35 lrwxrwxrwx 1 user users 19 2010-03-18 22:07 ld-uClibc.so.0 -> ld-uClibc-0.9.28.so
36 -rw-r--r-- 1 user users 11920 2010-03-18 13:27 libcrypt-0.9.28.so
37 lrwxrwxrwx 1 user users 18 2010-03-18 22:07 libcrypt.so.0 -> libcrypt-0.9.28.so
38 lrwxrwxrwx 1 user users 19 2010-03-18 22:07 libc.so.0 -> libuClibc-0.9.28.so
39 -rw-r--r-- 1 user users 7732 2010-03-18 13:27 libdl-0.9.28.so
40 lrwxrwxrwx 1 user users 15 2010-03-18 22:07 libdl.so.0 -> libdl-0.9.28.so
41 -rw-r--r-- 1 user users 134884 2010-03-18 13:27 libm-0.9.28.so
42 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 libm.so.0 -> libm-0.9.28.so
43 -rw-r--r-- 1 user users 1556 2010-03-18 13:27 libnsl-0.9.28.so
44 lrwxrwxrwx 1 user users 16 2010-03-18 22:07 libnsl.so.0 -> libnsl-0.9.28.so
45 -rw-r--r-- 1 user users 82864 2010-03-18 13:27 libpthread-0.9.28.so
46 lrwxrwxrwx 1 user users 20 2010-03-18 22:07 libpthread.so.0 -> libpthread-0.9.28.so
47 -rw-r--r-- 1 user users 1556 2010-03-18 13:27 libresolv-0.9.28.so
48 lrwxrwxrwx 1 user users 19 2010-03-18 22:07 libresolv.so.0 -> libresolv-0.9.28.so
49 -rw-r--r-- 1 user users 4532 2010-03-18 13:27 librt-0.9.28.so
50 lrwxrwxrwx 1 user users 15 2010-03-18 22:07 librt.so.0 -> librt-0.9.28.so
51 -rw-r--r-- 1 user users 432732 2010-03-18 13:27 libuClibc-0.9.28.so
52 -rw-r--r-- 1 user users 4952 2010-03-18 13:27 libutil-0.9.28.so
53 lrwxrwxrwx 1 user users 17 2010-03-18 22:07 libutil.so.0 -> libutil-0.9.28.so
54
55 ./proc:
56 total 0
57
58 ./sbin:
59 total 0
60 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 blkid -> ../bin/busybox
61 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 devfsd -> ../bin/busybox
62 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 fdisk -> ../bin/busybox
63 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 fsck -> ../bin/busybox
64 略去若干行
65 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 route -> ../bin/busybox
66 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 swapoff -> ../bin/busybox
67 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 swapon -> ../bin/busybox
68 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 syslogd -> ../bin/busybox
69 lrwxrwxrwx 1 user users 14 2010-03-18 22:07 udhcpc -> ../bin/busybox
70
71 ./tmp:
72 total 0
73
74 ./usr:
75 total 8
76 drwxr-xr-x 2 user users 4096 2010-03-18 22:09 bin
77 drwxr-xr-x 2 user users 4096 2010-03-18 22:10 sbin
78
79 ./usr/bin:
80 total 0
81 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 [ -> ../../bin/busybox
82 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 [[ -> ../../bin/busybox
83 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 awk -> ../../bin/busybox
84 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 basename -> ../../bin/busybox
85 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 bunzip2 -> ../../bin/busybox
86 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 bzcat -> ../../bin/busybox
87 略去若干行
88 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 wc -> ../../bin/busybox
89 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 wget -> ../../bin/busybox
90 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 which -> ../../bin/busybox
91 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 xargs -> ../../bin/busybox
92 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 yes -> ../../bin/busybox
93
94 ./usr/sbin:
95 total 0
96 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 chroot -> ../../bin/busybox
97 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 ftpd -> ../../bin/busybox
98 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 httpd -> ../../bin/busybox
99 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 inetd -> ../../bin/busybox
100 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 ntpd -> ../../bin/busybox
101 lrwxrwxrwx 1 user users 17 2010-03-18 22:08 telnetd -> ../../bin/busybox
102
103 ./var:
104 total 0
以下操作在播放机上执行
将U盘插入播放机，telnet到播放机，U盘应该已自动挂载到/tmp/usbmounts/sda1
1) 播放机默认将U盘挂载为只读模式，把它改为可读写模式
1 # mount -o remount,rw /tmp/usbmounts/sda1
2) 将/proc和/dev映射到模拟根文件系统。mount --bind 可将一个挂载点映射到另一个目录。
1 # mount --bind /proc /tmp/usbmounts/sda1/proc
2 # mount --bind /dev /tmp/usbmounts/sda1/dev
3) 复制/etc目录。chroot运行环境需要访问/etc下的文件。注意cp命令的大写的L参数，它使得符号连接作为普通文件拷贝。
1 # cp -rL /etc /tmp/usbmounts/sda1/
4) 执行chroot
1 # chroot /tmp/usbmounts/sda1
2
3
4 BusyBox v1.15.3 (2010-03-18 13:39:41 CST) built-in shell (ash)
5 Enter 'help' for a list of built-in commands.
6
7 # ls
8 bin dev etc lib proc sbin tmp usr var
9 #
可以看到BusyBox的版本好已经是1.15.3了，ls命令也正常执行了，这说明uClibc和BusyBox都正常工作。你还可以测试一些其它命令。
5)退出chroot环境
1 # exit
2 # umount /tmp/usbmounts/sda1/proc
3 # umount /tmp/usbmounts/sda1/dev
4 # mount -o remount,ro /tmp/usbmounts/sda1