I'm trying to figure out how CentOS 7 identifies what is considered a valid character in a naming convention when a user account is created.
I was playing around with useradd to confirm my understanding of what CentOS considered valid characters in a user name.... and to my surprise the useradd command accepted '_' and '.'... Which got me wondering where valid/invalid characters are established in CentOS
The useradd man page in CentOS doesn't mention valid characters... And google searches said this is done with NAME_REGEX (For ubuntu at least)... and had me looking for it in a adduser.conf file... which does not exist in CentOS 7... I haven't been able to locate a CentOS/Red Hat specific source on google about this... But I've also looked in /etc/login.defs and /etc/default/useradd with no luck
Can anyone direct me to the mechanism in CentOS does this?