How to do a proper substitution with sed?

Question

linux

There is a conditional config:

user = u1
second.user = u2

gotta get

user = my_u1
second.user = u2

doing
sed -i '/user/s/= .*/= my_u1/' ${PATH_CONFIG_FILE}
I get

user = my_u1
second.user = my_u1

Answer 1

sed -i '/^user/s/= .*/= my_user_1/' ${PATH_CONFIG_FILE}