TP-Link TL-WR703n路由USB口用途2——挂载U盘，从U盘启动

原文地址：http://blog.pickbox.me/2013/08/28/tp-link-tl-wr703n%E8%B7%AF%E7%94%B1usb%E5%8F%A3%E7%94%A8%E9%80%942-%E6%8C%82%E8%BD%BDu%E7%9B%98%EF%BC%8C%E4%BB%8Eu%E7%9B%98%E5%90%AF%E5%8A%A8/

这里先在自己的主Linux系统中格式化好U盘，就不用在Openwrt中格式化U盘了
挂载U盘需要安装一些pkg模块，我的空间不够用了，于是先恢复到刷Openwrt固件的原始状态（出厂设置）
重启路由的时候按住reset，可以看到蓝色LED灯闪烁，接着很快的闪烁，说明进入了恢复模式
这时用telnet登陆到192.168.1.1（电脑用网线连接到wr703n的LAN口），运行

mount_rootfirstbootreboot -f

这样就恢复到了固件的初始状态

接下来安装pkg

root@OpenWrt:/etc/config# opkg updateDownloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/Packages.gz.Updated list of available packages in /var/opkg-lists/attitude_adjustment.root@OpenWrt:/etc/config# dfFilesystem           1K-blocks      Used Available Use% Mounted onrootfs                    1088       216       872  20% //dev/root                 2048      2048         0 100% /romtmpfs                    14608       672     13936   5% /tmptmpfs                      512         0       512   0% /dev/dev/mtdblock3            1088       216       872  20% /overlayoverlayfs:/overlay        1088       216       872  20% /root@OpenWrt:/etc/config# opkg install kmod-usb-storage block-mount kmod-fs-ext4Installing kmod-usb-storage (3.3.8-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/kmod-usb-storage_3.3.8-1_ar71xx.ipk.Installing kmod-scsi-core (3.3.8-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/kmod-scsi-core_3.3.8-1_ar71xx.ipk.Installing block-mount (0.2.0-9) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/block-mount_0.2.0-9_ar71xx.ipk.Installing blkid (2.21.2-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/blkid_2.21.2-1_ar71xx.ipk.Installing libblkid (2.21.2-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/libblkid_2.21.2-1_ar71xx.ipk.Installing libuuid (2.21.2-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/libuuid_2.21.2-1_ar71xx.ipk.Installing swap-utils (2.21.2-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/swap-utils_2.21.2-1_ar71xx.ipk.Installing kmod-fs-ext4 (3.3.8-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/kmod-fs-ext4_3.3.8-1_ar71xx.ipk.Installing kmod-lib-crc16 (3.3.8-1) to root...Downloading http://downloads.openwrt.org/attitude_adjustment/12.09/ar71xx/generic/packages/kmod-lib-crc16_3.3.8-1_ar71xx.ipk.Configuring kmod-scsi-core.Configuring kmod-usb-storage.Configuring kmod-lib-crc16.Configuring libuuid.Configuring libblkid.Configuring blkid.Configuring swap-utils.Configuring block-mount.Configuring kmod-fs-ext4.root@OpenWrt:/etc/config# df -hFilesystem                Size      Used Available Use% Mounted onrootfs                    1.1M    640.0K    448.0K  59% //dev/root                 2.0M      2.0M         0 100% /romtmpfs                    14.3M    680.0K     13.6M   5% /tmptmpfs                   512.0K         0    512.0K   0% /dev/dev/mtdblock3            1.1M    640.0K    448.0K  59% /overlayoverlayfs:/overlay        1.1M    640.0K    448.0K  59% /

这里可以看到安装pkg用了大概400多K的空间

root@OpenWrt:/etc/config# ls /dev/bsg        mtd0ro     mtd4ro     mtdblock5  sda1       ttyS12     ttyS6bus        mtd1       mtd5       null       shm        ttyS13     ttyS7console    mtd1ro     mtd5ro     port       tty        ttyS14     ttyS8full       mtd2       mtdblock0  ppp        ttyATH0    ttyS15     ttyS9kmsg       mtd2ro     mtdblock1  ptmx       ttyS0      ttyS2      urandomlog        mtd3       mtdblock2  pts        ttyS1      ttyS3      watchdogmem        mtd3ro     mtdblock3  random     ttyS10     ttyS4      zeromtd0       mtd4       mtdblock4  sda        ttyS11     ttyS5

可以看到在/dev目录下多了sda和sda1，说明U盘被识别出来了
修改/etc/config/fstab文件：

root@OpenWrt:/etc/config# vi fstabconfig global automount        option from_fstab 1        option anon_mount 1config global autoswap        option from_fstab 1        option anon_swap 0config mount        option target   /overlay        option device   /dev/sda1        option fstype   ext4        option options  rw,sync        option enabled  1        option enabled_fsck 0config swap        option device   /dev/sda2        option enabled  0

执行下面命令使其生效：

root@OpenWrt:~# /etc/init.d/fstab enable

接下来将系统root内容拷贝至U盘：

mount /dev/sda1 /mntmkdir /tmp/rootmount -o bind / /tmp/rootcp -a /tmp/root/* /mnt/umount /tmp/root

修改U盘上的/mnt/etc/banner，最末尾处加一行boot from usb，标识是从U盘启动的系统

root@OpenWrt:~# vi /mnt/etc/banner  _______                     ________        __ |       |.-----.-----.-----.|  |  |  |.----.|  |_ |   -   ||  _  |  -__|     ||  |  |  ||   _||   _| |_______||   __|_____|__|__||________||__|  |____|          |__| W I R E L E S S   F R E E D O M ----------------------------------------------------- ATTITUDE ADJUSTMENT (12.09, r36088) -----------------------------------------------------  * 1/4 oz Vodka      Pour all ingredients into mixing  * 1/4 oz Gin        tin with ice, strain into glass.  * 1/4 oz Amaretto  * 1/4 oz Triple sec  * 1/4 oz Peach schnapps  * 1/4 oz Sour mix  * 1 splash Cranberry juice ----------------------------------------------------- boot from usb -----------------------------------------------------

重启路由后就可以使用了

root@OpenWrt:~# rebootroot@OpenWrt:~# df -hFilesystem                Size      Used Available Use% Mounted onrootfs                    7.4G    248.7M      6.8G   3% //dev/root                 2.0M      2.0M         0 100% /romtmpfs                    14.3M    380.0K     13.9M   3% /tmptmpfs                   512.0K         0    512.0K   0% /dev/dev/sda1                 7.4G    248.7M      6.8G   3% /overlayoverlayfs:/overlay        7.4G    248.7M      6.8G   3% /

可以看到，系统的存储空间变为7.4G了！

注：重刷openwrt固件后还想使用原来U盘，可能会碰到这样一个错误：/dev/sda1被挂载到了/tmp/overlay-disabled，解决办法是

cp /.extroot.md5sum /tmp/overlay-disabled/etc/extroot.md5sum