shadow/man/newgidmap.1.xml
Iker Pedrosa d5b15f8633 man: clarify subid delegation
Clarify that the subid delegation can only come from one source.
Moreover, add an example of what might happen if the subid source is NSS
and useradd is executed.

Related: https://github.com/shadow-maint/shadow/issues/331
2021-05-24 12:43:40 +02:00

198 lines
6.4 KiB
XML

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
<!-- SHADOW-CONFIG-HERE -->
]>
<refentry id='newgidmap.1'>
<refentryinfo>
<author>
<firstname>Eric</firstname>
<surname>Biederman</surname>
<contrib>Creation, 2013</contrib>
</author>
</refentryinfo>
<refmeta>
<refentrytitle>newgidmap</refentrytitle>
<manvolnum>1</manvolnum>
<refmiscinfo class="sectdesc">User Commands</refmiscinfo>
<refmiscinfo class="source">shadow-utils</refmiscinfo>
<refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo>
</refmeta>
<refnamediv id='name'>
<refname>newgidmap</refname>
<refpurpose>set the gid mapping of a user namespace</refpurpose>
</refnamediv>
<refsynopsisdiv id='synopsis'>
<cmdsynopsis>
<command>newgidmap</command>
<arg choice='plain'>
<replaceable>pid</replaceable>
</arg>
<arg choice='plain'>
<replaceable>gid</replaceable>
</arg>
<arg choice='plain'>
<replaceable>lowergid</replaceable>
</arg>
<arg choice='plain'>
<replaceable>count</replaceable>
</arg>
<arg choice='opt'>
<arg choice='plain'>
<replaceable>gid</replaceable>
</arg>
<arg choice='plain'>
<replaceable>lowergid</replaceable>
</arg>
<arg choice='plain'>
<replaceable>count</replaceable>
</arg>
<arg choice='opt'>
<replaceable>...</replaceable>
</arg>
</arg>
</cmdsynopsis>
</refsynopsisdiv>
<refsect1 id='description'>
<title>DESCRIPTION</title>
<para>
The <command>newgidmap</command> sets <filename>/proc/[pid]/gid_map</filename> based on its
command line arguments and the gids allowed. The subid delegation can come either from files
(<filename>/etc/subgid</filename>) or from the configured NSS subid module. Only one of them
can be chosen at a time. So, for example, if the subid source is configured as NSS and
<command>groupadd</command> is executed, then the command will fail and the entry will not be
created in <filename>/etc/subgid</filename>.
</para>
<para>
Note that the root group is not exempted from the requirement for a valid
<filename>/etc/subgid</filename> entry.
</para>
<para>
After the pid argument, <command>newgidmap</command> expects sets of 3 integers:
<variablelist>
<varlistentry>
<term>gid</term>
<listitem>
<para>
Beginning of the range of GIDs inside the user namespace.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>lowergid</term>
<listitem>
<para>
Beginning of the range of GIDs outside the user namespace.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>count</term>
<listitem>
<para>
Length of the ranges (both inside and outside the user namespace).
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para>
<command>newgidmap</command> verifies that the caller is the owner
of the process indicated by <option>pid</option> and that for each
of the above sets, each of the GIDs in the range [lowergid,
lowergid+count) is allowed to the caller according to
<filename>/etc/subgid</filename> before setting
<filename>/proc/[pid]/gid_map</filename>.
</para>
<para>
Note that newgidmap may be used only once for a given process.
</para>
</refsect1>
<refsect1 id='options'>
<title>OPTIONS</title>
<para>
There currently are no options to the <command>newgidmap</command> command.
</para>
<variablelist remap='IP'>
</variablelist>
</refsect1>
<refsect1 id='files'>
<title>FILES</title>
<variablelist>
<varlistentry>
<term><filename>/etc/subgid</filename></term>
<listitem>
<para>List of user's subordinate group IDs.</para>
</listitem>
</varlistentry>
<varlistentry>
<term><filename>/proc/[pid]/gid_map</filename></term>
<listitem>
<para>Mapping of gids from one between user namespaces.</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id='see_also'>
<title>SEE ALSO</title>
<para>
<citerefentry>
<refentrytitle>login.defs</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>newusers</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>subgid</refentrytitle><manvolnum>5</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>useradd</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>userdel</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>,
<citerefentry>
<refentrytitle>usermod</refentrytitle><manvolnum>8</manvolnum>
</citerefentry>.
</para>
</refsect1>
</refentry>