NEWGIDMAP(1) User Commands NEWGIDMAP(1)
newgidmap - set the gid mapping of a user namespace
newgidmap pid gid lowergid count [gid lowergid count [ ... ]]
The newgidmap sets /proc/[pid]/gid_map based on its command line arguments and the gids allowed. Subgid delegation can either be managed via /etc/subgid or through the configured NSS subid module. These options are mutually exclusive. Note that the root group is not exempted from the requirement for a valid /etc/subgid entry. After the pid argument, newgidmap expects sets of 3 integers: gid Beginning of the range of GIDs inside the user namespace. lowergid Beginning of the range of GIDs outside the user namespace. count Length of the ranges (both inside and outside the user namespace). newgidmap verifies that the caller is the owner of the process indicated by pid and that for each of the above sets, each of the GIDs in the range [lowergid, lowergid+count) is allowed to the caller according to /etc/subgid before setting /proc/[pid]/gid_map. Note that newgidmap 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 for /proc/[pid[. In this case, newgidmap will use openat(2) to open the gid_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 newgidmap command.
/etc/subgid List of user's subordinate group IDs. /proc/[pid]/gid_map Mapping of gids from one between user namespaces.
login.defs(5), newusers(8), subgid(5), useradd(8), userdel(8), usermod(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@example.com. This page was obtained from the project's upstream Git repository ⟨https://github.com/shadow-maint/shadow⟩ on 2023-06-23. (At that time, the date of the most recent commit that was found in the repository was 2023-06-22.) 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 firstname.lastname@example.org shadow-utils 4.11.1 06/23/2023 NEWGIDMAP(1)
Pages that refer to this page: getsubids(1), unshare(1), mount_setattr(2), subgid(5), subuid(5), user_namespaces(7)