When a user is created in Linux, their username can be seen publicly in the passwd file. Is there a hash set for that?
Linux user security
linux;security
yes, the user name is visible publicly. You can pick a pseudonym if you like, but the name has to be unique, and will be visible to the other usersIn addition to what @gilles has already stated. The primary key, unique identifier of a user is the uid which is the 3rd field in the password file, or in the below example the '1000`xenoterracide:x:1000:100::/home/xenoterracide:/bin/zshto create another user that's effectively the same you could addbob:x:1000:100::/home/xenoterracide:/bin/zshwhich has the same uid therefore is the same user. So unix uses an integer (or is it a short) to denote the actual user id. No hashes are needed outside of the users password.The password is hashed, but what type of hash is defined by pam configuration, in my case I'm using sha512.password required        pam_unix.so sha512 shadow nullok