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Diffstat (limited to 'man/subuid.5.xml')
| -rw-r--r-- | man/subuid.5.xml | 152 |
1 files changed, 152 insertions, 0 deletions
diff --git a/man/subuid.5.xml b/man/subuid.5.xml new file mode 100644 index 0000000..fc6b2c9 --- /dev/null +++ b/man/subuid.5.xml @@ -0,0 +1,152 @@ +<?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='subuid.5'> + <refentryinfo> + <author> + <firstname>Eric</firstname> + <surname>Biederman</surname> + <contrib>Creation, 2013</contrib> + </author> + <author> + <firstname>Iker</firstname> + <surname>Pedrosa</surname> + <contrib>Developer, 2021</contrib> + </author> + </refentryinfo> + <refmeta> + <refentrytitle>subuid</refentrytitle> + <manvolnum>5</manvolnum> + <refmiscinfo class="sectdesc">File Formats and Configuration Files</refmiscinfo> + <refmiscinfo class="source">shadow-utils</refmiscinfo> + <refmiscinfo class="version">&SHADOW_UTILS_VERSION;</refmiscinfo> + </refmeta> + <refnamediv id='name'> + <refname>subuid</refname> + <refpurpose>the configuration for subordinate user ids</refpurpose> + </refnamediv> + + <refsect1 id='description'> + <title>DESCRIPTION</title> + <para> + Subuid authorizes a user id to map ranges of user ids from its namespace + into child namespaces. + </para> + <para> + The delegation of the subordinate uids can be configured via the + <replaceable>subid</replaceable> field in + <filename>/etc/nsswitch.conf</filename> file. Only one value can be set + as the delegation source. Setting this field to + <replaceable>files</replaceable> configures the delegation of uids to + <filename>/etc/subuid</filename>. Setting any other value treats + the delegation as a plugin following with a name of the form + <replaceable>libsubid_$value.so</replaceable>. If the value or plugin is + missing, then the subordinate uid delegation falls back to + <replaceable>files</replaceable>. + </para> + <para> + Note, that <command>useradd</command> will only create entries in + <filename>/etc/subuid</filename> if subid delegation is managed via subid + files. + </para> + </refsect1> + + <refsect1 id='local-subordinate-delegation'> + <title>LOCAL SUBORDINATE DELEGATION</title> + <para> + Each line in <filename>/etc/subuid</filename> contains + a user name and a range of subordinate user ids that user + is allowed to use. + + This is specified with three fields delimited by colons + (<quote>:</quote>). + These fields are: + </para> + <itemizedlist mark='bullet'> + <listitem> + <para>login name or UID</para> + </listitem> + <listitem> + <para>numerical subordinate user ID</para> + </listitem> + <listitem> + <para>numerical subordinate user ID count</para> + </listitem> + </itemizedlist> + + <para> + This file specifies the user IDs that ordinary users can use, with + the <command>newuidmap</command> command, to configure uid mapping + in a user namespace. + </para> + + <para> + Multiple ranges may be specified per user. + </para> + + <para> + When large number of entries (10000-100000 or more) are defined in + <filename>/etc/subuid</filename>, parsing performance penalty will + become noticeable. In this case it is recommended to use UIDs + instead of login names. Benchmarks have shown speed-ups up to 20x. + </para> + + </refsect1> + + <refsect1 id='files'> + <title>FILES</title> + <variablelist> + <varlistentry> + <term><filename>/etc/subuid</filename></term> + <listitem> + <para>Per user subordinate user IDs.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><filename>/etc/subuid-</filename></term> + <listitem> + <para>Backup file for /etc/subuid.</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>newgidmap</refentrytitle><manvolnum>1</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>newuidmap</refentrytitle><manvolnum>1</manvolnum> + </citerefentry>, + <citerefentry> + <refentrytitle>newusers</refentrytitle><manvolnum>1</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>, + <citerefentry> + <refentrytitle>user_namespaces</refentrytitle><manvolnum>7</manvolnum> + </citerefentry>. + </para> + </refsect1> +</refentry> |