So,
just flashed the duo-buildroot-sdk-v2 to my Duo S.
how can I get more free space?`
[root@milkv-duo]~# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/root 756928 241672 460208 35% /
devtmpfs 161512 0 161512 0% /dev
tmpfs 161588 0 161588 0% /dev/shm
tmpfs 161588 124 161464 1% /tmp
tmpfs 161588 48 161540 1% /run