LU-4

There are 58 standard Chinese characters that have a 'lu' pronunciation. The most common sound-indicating component are 卢(11) and录 (11). Others are: 鲁 (6), 鹿 (5)

录 = lu(4) = to record

登录 = deng(1)lu(4) = to log in (e.g. to access email)

The opposite is:

登出 = deng(1)chu(1) = to log out

登 = to ascend, to climb, to publish