'\" t
.\"     Title: newuidmap
.\"    Author: Eric Biederman
.\" Generator: DocBook XSL Stylesheets vsnapshot <http://docbook.sf.net/>
.\"      Date: 07/02/2024
.\"    Manual: User Commands
.\"    Source: shadow-utils 4.16.0
.\"  Language: English
.\"
.TH "NEWUIDMAP" "1" "07/02/2024" "shadow\-utils 4\&.16\&.0" "User Commands"
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.SH "NAME"
newuidmap \- set the uid mapping of a user namespace
.SH "SYNOPSIS"
.HP \w'\fBnewuidmap\fR\ 'u
\fBnewuidmap\fR \fIpid\fR \fIuid\fR \fIloweruid\fR \fIcount\fR [\fIuid\fR\ \fIloweruid\fR\ \fIcount\fR\ [\ \fI\&.\&.\&.\fR\ ]]
.SH "DESCRIPTION"
.PP
The
\fBnewuidmap\fR
sets
/proc/[pid]/uid_map
based on its command line arguments and the uids allowed\&. Subuid delegation can either be managed via
/etc/subuid
or through the configured NSS subid module\&. These options are mutually exclusive\&.
.PP
Note that the root user is not exempted from the requirement for a valid
/etc/subuid
entry\&.
.PP
After the pid argument,
\fBnewuidmap\fR
expects sets of 3 integers:
.PP
uid
.RS 4
Beginning of the range of UIDs inside the user namespace\&.
.RE
.PP
loweruid
.RS 4
Beginning of the range of UIDs outside the user namespace\&.
.RE
.PP
count
.RS 4
Length of the ranges (both inside and outside the user namespace)\&.
.RE
.PP
\fBnewuidmap\fR
verifies that the caller is the owner of the process indicated by
\fBpid\fR
and that for each of the above sets, each of the UIDs in the range [loweruid, loweruid+count) is allowed to the caller according to
/etc/subuid
before setting
/proc/[pid]/uid_map\&.
.PP
Note that newuidmap may be used only once for a given process\&.
.PP
Instead of an integer process id, the first argument may be specified as
\fIfd:N\fR, where the integer N is the file descriptor number for the calling process\*(Aqs opened file descriptor for the directory
/proc/[pid]\&. In this case,
\fBnewuidmap\fR
will use
openat(2)
to open the
uid_map
file under that directory, avoiding a TOCTTOU in case the process exits and the pid is immediately reused\&.
.SH "OPTIONS"
.PP
There currently are no options to the
\fBnewuidmap\fR
command\&.
.SH "FILES"
.PP
/etc/subuid
.RS 4
List of user\*(Aqs subordinate user IDs\&.
.RE
.PP
/proc/[pid]/uid_map
.RS 4
Mapping of uids from one between user namespaces\&.
.RE
.SH "SEE ALSO"
.PP
\fBlogin.defs\fR(5),
\fBnewusers\fR(8),
\fBsubuid\fR(5),
\fBuseradd\fR(8),
\fBusermod\fR(8),
\fBuserdel\fR(8)\&.