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<?xml version="1.0" encoding="UTF-8"?>
<!--
SPDX-FileCopyrightText: 2013 Eric W. Biederman
SPDX-License-Identifier: BSD-3-Clause
-->
<!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. Subgid
delegation can either be managed via <filename>/etc/subgid</filename>
or through the configured NSS subid module. These options are mutually
exclusive.
</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>
<para>
Instead of an integer process id, the first argument may be
specified as <replaceable>fd:N</replaceable>, where the integer N
is the file descriptor number for the calling process's opened
file descriptor for the directory <filename>/proc/[pid]</filename>.
In this case, <command>newgidmap</command> will use
<refentrytitle>openat</refentrytitle><manvolnum>2</manvolnum>
to open the <filename>gid_map</filename> file under that
directory, avoiding a TOCTTOU in case the process exits and
the pid is immediately reused.
</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>
|
