Thanks to the command "cpuinfo", I've noticed that the "System type" is MediaTek MT7620, "cpu model" is MIPS 24KEc V5.0, so that I downloaded this package
So I believe that I have got the correct package for my machine, but I can't install it, I use
opkg install /path/to/bash_4.3.39-1_ramips_24kec.ipk, sure the path is right, and I got
Unknown package 'bash'.
pkg_hash_fetch_best_installation_candidate: Packages for bash found, but incompatible with the architectures configured
opkg_install_cmd: Cannot install package bash.
From the report, I don't think I need to install something else first (Am I wrong?), and I have no idea how to solve this problem.
UPDATE: The machine runs Pandorabox R2 14.09, with Luci Trunk (0.12+svn-r1024), I have also tried using bash_4.2-5_ramips_24kec.ipk from Index of /barrier_breaker/14.07/ramips/mt7620a/packages/packages/ and Index of /barrier_breaker/14.07/ramips/mt7620n/packages/packages/ I got the same report.
If I am not wrong, the version of firmware of OpenWrt should be 14.07, that's the base of Pandorabox R2 14.09.