xml/schema/unix.xsd

<?xml version="1.0" encoding="UTF-8" ?>
<xs:schema targetNamespace="http://schema.xml.r00t2.io/unix.xsd"
           xmlns="http://schema.xml.r00t2.io/unix.xsd"
           xmlns:unix="http://schema.xml.r00t2.io/unix.xsd"
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified"
           attributeFormDefault="qualified">

    <xs:simpleType name="t_posixUserGroup">
        <!-- https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_437
             https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap03.html#tag_03_282
             https://unix.stackexchange.com/a/435120/284004 -->
        <xs:restriction base="xs:token">
            <xs:pattern value="[a-z_]([a-z0-9_-]{0,31}|[a-z0-9_-]{0,30}$)"/>
            <xs:whiteSpace value="collapse"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="t_passwd_hashtypes">
        <xs:restriction base="xs:string">
            <xs:enumeration value="md5"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:simpleType name="t_shadowhash">
        <!-- http://man7.org/linux/man-pages/man3/crypt.3.html#NOTES -->
        <xs:restriction base="xs:token">
            <xs:pattern value="($1)?($[a-zA-Z0-9./]{1,16})$[a-zA-Z0-9./]{22}"/><!-- md5 -->
            <xs:whiteSpace value="collapse"/>
        </xs:restriction>
    </xs:simpleType>

</xs:schema>