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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | FILES | SEE ALSO | COLOPHON |
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NEWUIDMAP(1) User Commands NEWUIDMAP(1)
newuidmap - set the uid mapping of a user namespace
newuidmap pid uid loweruid count [uid loweruid count [ ... ]]
The newuidmap 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.
Note that the root user is not exempted from the requirement for a
valid /etc/subuid entry.
After the pid argument, newuidmap expects sets of 3 integers:
uid
Beginning of the range of UIDs inside the user namespace.
loweruid
Beginning of the range of UIDs outside the user namespace.
count
Length of the ranges (both inside and outside the user
namespace).
newuidmap verifies that the caller is the owner of the process
indicated by pid 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.
Note that newuidmap may be used only once for a given process.
Instead of an integer process id, the first argument may be
specified as fd:N, where the integer N is the file descriptor
number for the calling process's opened file descriptor for the
directory /proc/[pid]. In this case, newuidmap 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.
There currently are no options to the newuidmap command.
/etc/subuid
List of user's subordinate user IDs.
/proc/[pid]/uid_map
Mapping of uids from one between user namespaces.
login.defs(5), newusers(8), subuid(5), useradd(8), usermod(8),
userdel(8).
This page is part of the shadow-utils (utilities for managing
accounts and shadow password files) project. Information about
the project can be found at
⟨https://github.com/shadow-maint/shadow⟩. If you have a bug report
for this manual page, send it to
[email protected]. This page was obtained
from the project's upstream Git repository
⟨https://github.com/shadow-maint/shadow⟩ on 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-10.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
shadow-utils 4.18.0 08/11/2025 NEWUIDMAP(1)
Pages that refer to this page: getsubids(1), unshare(1), mount_setattr(2), subgid(5), subuid(5), user_namespaces(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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