newuidmap man page
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 in /etc/subuid. 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:
Beginning of the range of UIDs inside the user namespace.
Beginning of the range of UIDs outside the user namespace.
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.
There currently are no options to the newuidmap command.
List of user's subordinate user IDs.
Mapping of uids from one between user namespaces.
login.defs(5), newusers(8), subuid(5), useradd(8), usermod(8), userdel(8).
buildah(1), buildah-unshare(1), subgid(5), subuid(5), user_namespaces(7).