Java™ Application Development on Linux - Dator

20.3 Be an Enabler, or “Let’s Be Codependent!”447Imagine that user names bob, ted, carol, and alice are part ofcarl and michael’s Web development team and each has an account onthe box on which we intend to install JBoss.So, we create a group entry in the /etc/group file:local:x:100:carl,michael,bob,carol,ted,aliceIf Bob later leaves to join the custodial staff, simply remove his namefrom the group and he loses his access.TIPThe user’s default group is specified in the /etc/passwd file. Here’s a sample:mschwarz:x:500:500:Michael Schwarz:/home/mschwarz:/bin/bashThe fields of this are:username:passwd:uid:gid:userinfo:homedir:loginprogwhere:• username is the login name of the user.• passwd is the user’s encrypted password. Or rather it used to be. Now,this is usually x and the encrypted password is stored in the/etc/shadow file. This is because /etc/passwd must be worldreadable.The shadow file is not. This prevents someone reading theencrypted passwords to do an offline dictionary attack.• uid is the numeric user ID associated with this username.• gid is the numeric group ID of this user’s default group. Look for thisnumber in /etc/group to find the name of the default group.• userinfo is additional information about this user. Sometimes called thegecos field for obscure historical reasons, 5 this field usually stores theuser’s real name and possibly other information like office location andphone number.• homedir is the user’s home directory.• loginprog is the name of the program that will be executed when theuser logs in. This is usually a shell, but it may be any program.5. See http://www.hyperdictionary.com/dictionary/GCOS if you are dying toknow why.