U-boot: bad magic number

I'am using Arduino Yun and i want mount rootfs over NFS. I downloaded openwrt sources, build the project and then copied the generated rootfs from build_dir/target-mips_34kc_musl-1.1.15/root-ar71xx under /home/user/srv/nfs/root-ar71xx in the uboot prompt the command line i used is : setenv bootargs root=/dev/nfs rw nfsroot=192.168.1.1:/home/user/srv/nfs/root-ar71xx ip=192.168.1.2:192.168.1.1:192.168.1.1:255.255.255.0::off; bootm uboot environement variables: ar7240> printenv bootcmd=bootm 0x9fea0000 bootdelay=4 baudrate=115200 ethaddr=0xb4:0x21:0x8a:0x00:0x00:0x10 ipaddr=192.168.1.2 serverip=192.168.1.1 stdin=serial stdout=serial stderr=serial ethact=eth0 bootargs=root=/dev/nfs rw nfsroot=192.168.1.1:/home/user/srv/nfs/root-ar71xx ip=192.168.1.2:192.168.1.1:192.168.1.1:255.255.255.0::off Environment size: 319/65532 bytes But i got : ## Booting image at 81000000 ... Bad Magic Number I read in [this link](http://lists.denx.de/pipermail/u-boot/2006-May/014983.html) , that there is a kind of encapsulation for the kernel in order to be "known" by U-Boot. Is it the same thing for the rootfs I have another question but it's not very related to the topic: After building the project i have several binaries (24) under bin/ar71xx/: openwrt-ar71xx-generic-wzr-hp-ag300h-squashfs-tftp.bin openwrt-ar71xx-generic-tl-mr11u-v1-squashfs-sysupgrade.bin openwrt-ar71xx-generic-wzr-hp-g300nh2-squashfs-factory.bin ... I expect only one kernel image what all these images are supposed to do ? Thanks in advance. **EDIT**: I change the cmd line to : setenv bootargs root=/dev/nfs rw nfsroot=192.168.1.1:/home/bou6/srv /nfs/root-ar71xx ip=192.168.1.2:192.168.1.1:192.168.1.1:255.255.255.0::off; bootm 0x9fea0000 and i don"t have Bad Magic Number anymore, but still questions: 1- How can we know the load address of the kernel 2- I noticed even though the ethernet cable is not branched the kernel continue to use the default file system flashed on the Yun, is there a method to desactivate this.