diff -urpa shadow-4.8.orig/libmisc/chkname.c shadow-4.8/libmisc/chkname.c
--- shadow-4.8.orig/libmisc/chkname.c	2019-10-05 03:23:58.000000000 +0200
+++ shadow-4.8/libmisc/chkname.c	2019-12-15 23:50:06.137000000 +0100
@@ -55,21 +55,28 @@ static bool is_valid_name (const char *n
 	}
 
 	/*
-	 * User/group names must match [a-z_][a-z0-9_-]*[$]
+	 * User/group names must match gnu e-regex:
+	 *    [a-zA-Z0-9_.][a-zA-Z0-9_.-]{0,30}[a-zA-Z0-9_.$-]?
+	 *
+	 * as a non-POSIX, extension, allow "$" as the last char for
+	 * sake of Samba 3.x "add machine script"
 	 */
-
-	if (('\0' == *name) ||
-	    !((('a' <= *name) && ('z' >= *name)) || ('_' == *name))) {
+	if ( ('\0' == *name) ||
+	    !((*name >= 'a' && *name <= 'z') ||
+		(*name >= 'A' && *name <= 'Z') ||
+		(*name >= '0' && *name <= '9') ||
+		(*name == '_') || (*name == '.')
+	    )) {
 		return false;
 	}
 
 	while ('\0' != *++name) {
-		if (!(( ('a' <= *name) && ('z' >= *name) ) ||
-		      ( ('0' <= *name) && ('9' >= *name) ) ||
-		      ('_' == *name) ||
-		      ('-' == *name) ||
-		      ( ('$' == *name) && ('\0' == *(name + 1)) )
-		     )) {
+		if (!(  (*name >= 'a' && *name <= 'z') ||
+			(*name >= 'A' && *name <= 'Z') ||
+			(*name >= '0' && *name <= '9') ||
+			(*name == '_') || (*name == '.') || (*name == '-') ||
+			(*name == '$' && *(name + 1) == '\0')
+		)) {
 			return false;
 		}
 	}
diff -urpa shadow-4.8.orig/man/groupadd.8.xml shadow-4.8/man/groupadd.8.xml
--- shadow-4.8.orig/man/groupadd.8.xml	2019-07-23 17:26:08.000000000 +0200
+++ shadow-4.8/man/groupadd.8.xml	2019-12-15 23:41:44.562000000 +0100
@@ -273,12 +273,6 @@
    <refsect1 id='caveats'>
      <title>CAVEATS</title>
      <para>
-       Groupnames must start with a lower case letter or an underscore,
-       followed by lower case letters, digits, underscores, or dashes.
-       They can end with a dollar sign.
-       In regular expression terms: [a-z_][a-z0-9_-]*[$]?
-     </para>
-     <para>
        Groupnames may only be up to &GROUP_NAME_MAX_LENGTH; characters long.
      </para>
      <para>
diff -urpa shadow-4.8.orig/man/man8/groupadd.8 shadow-4.8/man/man8/groupadd.8
--- shadow-4.8.orig/man/man8/groupadd.8	2019-12-01 18:45:34.000000000 +0100
+++ shadow-4.8/man/man8/groupadd.8	2019-12-15 23:41:44.563000000 +0100
@@ -197,9 +197,7 @@ Shadow password suite configuration\&.
 .RE
 .SH "CAVEATS"
 .PP
-Groupnames must start with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes\&. They can end with a dollar sign\&. In regular expression terms: [a\-z_][a\-z0\-9_\-]*[$]?
-.PP
-Groupnames may only be up to 16 characters long\&.
+Groupnames may only be up to 32 characters long\&.
 .PP
 You may not add a NIS or LDAP group\&. This must be performed on the corresponding server\&.
 .PP
diff -urpa shadow-4.8.orig/man/man8/useradd.8 shadow-4.8/man/man8/useradd.8
--- shadow-4.8.orig/man/man8/useradd.8	2019-12-01 18:45:38.000000000 +0100
+++ shadow-4.8/man/man8/useradd.8	2019-12-15 23:41:44.563000000 +0100
@@ -226,7 +226,7 @@ is not enabled, no home directories are
 .PP
 \fB\-M\fR, \fB\-\-no\-create\-home\fR
 .RS 4
-Do no create the user\*(Aqs home directory, even if the system wide setting from
+Do not create the user\*(Aqs home directory, even if the system wide setting from
 /etc/login\&.defs
 (\fBCREATE_HOME\fR) is set to
 \fIyes\fR\&.
@@ -440,8 +440,6 @@ Similarly, if the username already exist
 \fBuseradd\fR
 will deny the user account creation request\&.
 .PP
-Usernames must start with a lower case letter or an underscore, followed by lower case letters, digits, underscores, or dashes\&. They can end with a dollar sign\&. In regular expression terms: [a\-z_][a\-z0\-9_\-]*[$]?
-.PP
 Usernames may only be up to 32 characters long\&.
 .SH "CONFIGURATION"
 .PP
diff -urpa shadow-4.8.orig/man/useradd.8.xml shadow-4.8/man/useradd.8.xml
--- shadow-4.8.orig/man/useradd.8.xml	2019-10-05 03:23:58.000000000 +0200
+++ shadow-4.8/man/useradd.8.xml	2019-12-15 23:41:44.563000000 +0100
@@ -366,7 +366,7 @@
 	</term>
 	<listitem>
 	  <para>
-	    Do no create the user's home directory, even if the system
+	    Do not create the user's home directory, even if the system
 	    wide setting from <filename>/etc/login.defs</filename>
 	    (<option>CREATE_HOME</option>) is set to
 	    <replaceable>yes</replaceable>.
@@ -661,12 +661,6 @@
     </para>
 
     <para>
-      Usernames must start with a lower case letter or an underscore,
-      followed by lower case letters, digits, underscores, or dashes.
-      They can end with a dollar sign.
-      In regular expression terms: [a-z_][a-z0-9_-]*[$]?
-    </para>
-    <para>
       Usernames may only be up to 32 characters long.
     </para>
   </refsect1>