My unix skills are rusty and did work on it long time back(AIX, Solaris). I never heard sudo command since I only used 'su'.

After researching this is what I understood. I installed rootsh for custom ring tones. So this installed 'gainroot' command in /usr/sbin. I am assuming that gainroot is same as rootsh. sudo is su+ command on same line

I don't think I ever set root password on my n900.