Balint Reczey
101 lines
2.6 KiB
Plaintext
101 lines
2.6 KiB
Plaintext
'\" t
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.\" Title: subuid
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.\" Author: Eric Biederman
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.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
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.\" Date: 01/23/2020
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.\" Manual: File Formats and Conversions
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.\" Source: shadow-utils 4.8.1
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.\" Language: English
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.\"
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.TH "SUBUID" "5" "01/23/2020" "shadow\-utils 4\&.8\&.1" "File Formats and Conversions"
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.\" -----------------------------------------------------------------
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.\" * Define some portability stuff
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.\" -----------------------------------------------------------------
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.\" http://bugs.debian.org/507673
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.\" ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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.ie \n(.g .ds Aq \(aq
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.el .ds Aq '
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.\" -----------------------------------------------------------------
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.\" * set default formatting
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.\" -----------------------------------------------------------------
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.\" disable hyphenation
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.nh
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.\" disable justification (adjust text to left margin only)
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.ad l
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.\" -----------------------------------------------------------------
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.\" * MAIN CONTENT STARTS HERE *
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.\" -----------------------------------------------------------------
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.SH "NAME"
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subuid \- the subordinate uid file
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.SH "DESCRIPTION"
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.PP
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Each line in
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/etc/subuid
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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 (\(lq:\(rq)\&. These fields are:
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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login name or UID
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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numerical subordinate user ID
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.RE
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.sp
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.RS 4
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.ie n \{\
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\h'-04'\(bu\h'+03'\c
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.\}
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.el \{\
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.sp -1
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.IP \(bu 2.3
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.\}
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numerical subordinate user ID count
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.RE
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.PP
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This file specifies the user IDs that ordinary users can use, with the
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\fBnewuidmap\fR
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command, to configure uid mapping in a user namespace\&.
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.PP
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Multiple ranges may be specified per user\&.
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.PP
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When large number of entries (10000\-100000 or more) are defined in
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/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\&.
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.SH "FILES"
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.PP
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/etc/subuid
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.RS 4
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Per user subordinate user IDs\&.
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.RE
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.PP
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/etc/subuid\-
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.RS 4
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Backup file for /etc/subuid\&.
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.RE
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.SH "SEE ALSO"
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.PP
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\fBlogin.defs\fR(5),
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\fBnewgidmap\fR(1),
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\fBnewuidmap\fR(1),
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\fBnewusers\fR(1),
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\fBsubgid\fR(5),
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\fBuseradd\fR(8),
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\fBuserdel\fR(8),
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\fBusermod\fR(8),
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\fBuser_namespaces\fR(7)\&.
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