man-pages/man5/subuid.5.html
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<H1>SUBUID</H1>
Section: File Formats and Conversions (5)<BR>Updated: 05/28/2020<BR><A HREF="#index">Index</A>
<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
<A NAME="lbAB">&nbsp;</A>
<H2>NAME</H2>
subuid - the subordinate uid file
<A NAME="lbAC">&nbsp;</A>
<H2>DESCRIPTION</H2>
<P>
Each line in
/etc/subuid
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 (":"). These fields are:
<P>
<DL COMPACT><DT id="1"><DD>
&bull;
login name or UID
</DL>
<P>
<DL COMPACT><DT id="2"><DD>
&bull;
numerical subordinate user ID
</DL>
<P>
<DL COMPACT><DT id="3"><DD>
&bull;
numerical subordinate user ID count
</DL>
<P>
This file specifies the user IDs that ordinary users can use, with the
<B>newuidmap</B>
command, to configure uid mapping in a user namespace.
<P>
Multiple ranges may be specified per user.
<P>
When large number of entries (10000-100000 or more) are defined in
/etc/subuid, 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.
<A NAME="lbAD">&nbsp;</A>
<H2>FILES</H2>
<P>
/etc/subuid
<DL COMPACT><DT id="4"><DD>
Per user subordinate user IDs.
</DL>
<P>
/etc/subuid-
<DL COMPACT><DT id="5"><DD>
Backup file for /etc/subuid.
</DL>
<A NAME="lbAE">&nbsp;</A>
<H2>SEE ALSO</H2>
<P>
<B><A HREF="/cgi-bin/man/man2html?5+login.defs">login.defs</A></B>(5),
<B><A HREF="/cgi-bin/man/man2html?1+newgidmap">newgidmap</A></B>(1),
<B><A HREF="/cgi-bin/man/man2html?1+newuidmap">newuidmap</A></B>(1),
<B><A HREF="/cgi-bin/man/man2html?1+newusers">newusers</A></B>(1),
<B><A HREF="/cgi-bin/man/man2html?5+subgid">subgid</A></B>(5),
<B><A HREF="/cgi-bin/man/man2html?8+useradd">useradd</A></B>(8),
<B><A HREF="/cgi-bin/man/man2html?8+userdel">userdel</A></B>(8),
<B><A HREF="/cgi-bin/man/man2html?8+usermod">usermod</A></B>(8),
<B><A HREF="/cgi-bin/man/man2html?7+user_namespaces">user_namespaces</A></B>(7).
<P>
<HR>
<A NAME="index">&nbsp;</A><H2>Index</H2>
<DL>
<DT id="6"><A HREF="#lbAB">NAME</A><DD>
<DT id="7"><A HREF="#lbAC">DESCRIPTION</A><DD>
<DT id="8"><A HREF="#lbAD">FILES</A><DD>
<DT id="9"><A HREF="#lbAE">SEE ALSO</A><DD>
</DL>
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Time: 00:06:06 GMT, March 31, 2021
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