.\" Copyright 2016, Michael Kerrisk .\" Copyright 2016, Eugene Syromyatnikov .\" A very few fragments remain from an earlier version of this page .\" written by David Howells (dhowells@redhat.com) .\" Copyright 2024, Alejandro Colomar .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .TH KEYCTL_UPDATE 2const 2024-08-21 "Linux man-pages 6.10" .SH NAME KEYCTL_UPDATE \- update a key's data payload .SH LIBRARY Standard C library .RI ( libc ,\~ \-lc ) .SH SYNOPSIS .nf .BR "#include " " /* Definition of " KEY* " constants */" .BR "#include " " /* Definition of " SYS_* " constants */" .B #include .P .BI "long syscall(SYS_keyctl, KEYCTL_UPDATE, key_serial_t " key , .BI " void " payload [. size "], size_t " size ); .fi .SH DESCRIPTION Update a key's data payload. .P .I key specifies the ID of the key to be updated. .I payload points to the new payload and .I size contains the new payload size in bytes. .P The caller must have .I write permission on the key specified and the key type must support updating. .P A negatively instantiated key (see .BR KEYCTL_REJECT (2const)) can be positively instantiated with this operation. .SH RETURN VALUE On success, 0 is returned. .P On error, \-1 is returned, and .I errno is set to indicate the error. .SH ERRORS .TP The key type does not support updating. .SH VERSIONS A wrapper is provided in the .I libkeyutils library: .BR keyctl_update (3). .SH STANDARDS Linux. .SH HISTORY Linux 2.6.10. .SH SEE ALSO .BR keyctl (2), .BR keyctl_update (3)