Thanks for your reply. I actually found this in http://www.yoctoproject.org/docs/1.6.1/kernel-dev/kernel-dev.html as well so I could get Step6 ii worked without error, but still have same error for Step6 iii. Any hints would help, thanks!
ERROR: Unable to spawn terminal auto: Execution of ‘/home/mangoh/legato/yk/downloads/yocto/build_bin/tmp/work/swi_mdm9x15-poky-linux-gnueabi/linux-yocto/3.14.29+gitAUTOINC+a00e464379_b0ce579abb-r0.1/temp/run.do_terminal.3387’ failed with exit code 1:
Option “-t” is no longer supported in this version of gnome-terminal.
Error constructing proxy for org.gnome.Terminal:/org/gnome/Terminal/Factory0: Error calling StartServiceByName for org.gnome.Terminal: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.gnome.Terminal exited with status 8
ERROR: Function failed: do_menuconfig
ERROR: Logfile of failure stored in: /home/mangoh/legato/yk/downloads/yocto/build_bin/tmp/work/swi_mdm9x15-poky-linux-gnueabi/linux-yocto/3.14.29+gitAUTOINC+a00e464379_b0ce579abb-r0.1/temp/log.do_menuconfig.3387
ERROR: Task 7 (/home/mangoh/legato/yk/downloads/yocto/poky/meta/recipes-kernel/linux/linux-yocto_3.14.bb, do_menuconfig) failed with exit code ‘1’