diff -up shadow-4.5/libmisc/chkname.c.goodname shadow-4.5/libmisc/chkname.c
--- shadow-4.5/libmisc/chkname.c.goodname	2014-09-01 16:36:40.000000000 +0200
+++ shadow-4.5/libmisc/chkname.c	2017-09-15 17:06:29.917939977 +0200
@@ -47,27 +47,46 @@
 #include "chkname.h"
 
 static bool is_valid_name (const char *name)
-{
+{      
 	/*
-	 * User/group names must match [a-z_][a-z0-9_-]*[$]
-	 */
-	if (('\0' == *name) ||
-	    !((('a' <= *name) && ('z' >= *name)) || ('_' == *name))) {
+         * User/group names must match gnu e-regex:
+         *    [a-zA-Z0-9_.][a-zA-Z0-9_.-]{0,30}[a-zA-Z0-9_.$-]?
+         *
+         * as a non-POSIX, extension, allow "$" as the last char for
+         * sake of Samba 3.x "add machine script"
+         *
+         * Also do not allow fully numeric names or just "." or "..".
+         */
+	int numeric;
+
+	if ('\0' == *name ||
+	    ('.' == *name && (('.' == name[1] && '\0' == name[2]) ||
+			      '\0' == name[1])) ||
+	    !((*name >= 'a' && *name <= 'z') ||
+	      (*name >= 'A' && *name <= 'Z') ||
+	      (*name >= '0' && *name <= '9') ||
+	      *name == '_' ||
+	      *name == '.')) {
 		return false;
 	}
 
+	numeric = isdigit(*name);
+
 	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;
 		}
+		numeric &= isdigit(*name);
 	}
 
-	return true;
+	return !numeric;
 }
 
 bool is_valid_user_name (const char *name)
diff -up shadow-4.5/man/groupadd.8.xml.goodname shadow-4.5/man/groupadd.8.xml
--- shadow-4.5/man/groupadd.8.xml.goodname	2014-09-01 16:36:40.000000000 +0200
+++ shadow-4.5/man/groupadd.8.xml	2017-08-14 10:27:24.657391521 +0200
@@ -256,12 +256,6 @@
    <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 -up shadow-4.5/man/useradd.8.xml.goodname shadow-4.5/man/useradd.8.xml
--- shadow-4.5/man/useradd.8.xml.goodname	2016-08-15 04:48:14.000000000 +0200
+++ shadow-4.5/man/useradd.8.xml	2017-08-14 10:27:24.667391382 +0200
@@ -347,6 +347,11 @@
 	    <option>CREATE_HOME</option> is not enabled, no home
 	    directories are created.
 	  </para>
+	  <para>
+	    The directory where the user's home directory is created must
+	    exist and have proper SELinux context and permissions. Otherwise
+	    the user's home directory cannot be created or accessed.
+	  </para>
 	</listitem>
       </varlistentry>
       <varlistentry>
@@ -355,7 +360,7 @@
 	</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>.
@@ -633,12 +638,6 @@
     </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>