mongodb - Can't create user -

i using mongodb version 2.6.6 on google compute engine , used click deploy method.

rs0:secondary> db.createuser({user:"admin", pwd:"secret_password", roles:[{role:"root", db:"admin"}]}) 2015-07-13t15:02:28.434+0000 error: couldn't add user: not master @ src/mongo/shell/db.js:1004  rs0:secondary> use admin switched db admin rs0:secondary> db.createuser({user:"admin", pwd:"secret_password", roles:["root"]}) 2015-07-13t15:13:28.591+0000 error: couldn't add user: not master @ src/mongo/shell/db.js:1004 

mongodb deployed in cluster of compute engine instances (also known mongodb replica set). each instance use boot disk , separate disk database files.

primary , master nodes nodes can accept writes. mongodb’s replication “single-master:” 1 node can accept write operations @ time.

secondary , slave nodes read-only nodes replicate primary.

you error message looks trying add user on secondary. try adding user in primary.