CAPNG_SET_ROOTID(3)              Libcap-ng API             CAPNG_SET_ROOTID(3)

NAME
       capng_set_rootid - set namespace root id

SYNOPSIS
       #include <cap-ng.h>

       int capng_set_rootid(uid_t rootid);


DESCRIPTION
       capng_set_rootid sets the root user ID for file capabilities
       operations. The value is host-endian and relative to the caller's user
       namespace. Pass CAPNG_UNSET_ROOTID to clear a previously selected
       namespace root ID and go back to writing regular V2 file capabilities.
       Other values select V3 file capabilities; the kernel validates and maps
       the user ID when the capabilities are written.


RETURN VALUE
       On success, it returns 0. It returns -1 if there is an internal error
       or the kernel headers used to build the library do not support V3 file
       capabilities.


SEE ALSO
       capng_apply_caps_fd(3), capabilities(7)


AUTHOR
       Steve Grubb

Red Hat                           March 2026               CAPNG_SET_ROOTID(3)