linux default user names

Quote:

Originally posted here by newtolinux
Can anyone explain what is the purpose of default user names in linux like bin,halt,shutdown...
I see these entries in /etc/passwd file

All helps are much appreciated.

Most is for security. Most of the usernames you will see there are locked accounts (shell is /bin/nologin) and are used to control, usually, daemons (like your web server, email server, etc). By having normal users as the owners of the daemon and having seperate users for the daemons, if a daemon was compromised the access obtained would be limited to the privelages of that user. I am not sure about default linux file permissions (still learning myself), but in Solaris, if you have locked down file permisisons, you can make it much more difficult for someone that has obtained user level access to escalate their privelages to root (where they can cause significantly more damage).