I was trying to create a samba share that is readonly for guests and writable for the root user. Writing the steps here as a note for myself and other people
Disable built-in samba server in CoreELEC settings. I couldn’t add samba user with it because smbpasswd is readonly.
Copy group and passwd to /opt/etc as mentioned here
# rm /opt/etc/passwd /opt/etc/shadow /opt/etc/group
# cp /etc/passwd /etc/shadow /etc/group /opt/etc
install entware (skip this if you already have it)
# installentware
install samba4-server from entware
# opkg update && opkg install samba4-server
setup a samba password for the root user
# smbpasswd -a root
New SMB password:[password]
Retype new SMB password:[password]
Example samba share. Anyone without root password will have readonly access. Anyone with samba root password will have full access
[external]
path = /var/media/external
available = yes
browseable = yes
public = yes
writeable = yes
write list = root
read list = nobody
root preexec = mkdir -p /var/media/external
restart samba
# /storage/.opt/etc/init.d/S91smb restart