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.\" Copyright (C) 1995, Thomas K. Dyas <tdyas@eden.rutgers.edu>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date. The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein. The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" Created Sun Aug 6 1995 Thomas K. Dyas <tdyas@eden.rutgers.edu>
.\"
.TH SETFSGID 2 "6 August 1995" "Linux 1.3.15" "Linux Programmer's Manual"
.SH NAME
setfsgid \- set group identity used for file system checks
.SH SYNOPSIS
.BI "int setfsgid(uid_t " fsgid )
.SH DESCRIPTION
.B setfsgid
sets the group ID that the Linux kernel uses to check for all accesses
to the file system. Normally, the value of
.I fsgid
will shadow the value of the effective group ID. In fact, whenever the
effective group ID is changed,
.I fsgid
will also be changed to new value of effective group ID.
An explicit call to
.B setfsgid
is usually only used by programs such as the Linux NFS server that
need to change what group ID is used for file access without a
corresponding change in the real and effective group IDs. A change in
the normal group IDs for a program such as the NFS server is a
security hole that can expose it to unwanted signals from other group
IDs.
.B setfsgid
will only succeed if the caller is the superuser or if
.I fsgid
matches either the real group ID, effective group ID,
saved set-group-ID, or the current value of
.IR fsgid .
.SH "RETURN VALUE"
On success, the previous value of
.I fsgid
is returned. On error, the current value of
.I fsgid
is returned.
.SH "CONFORMING TO"
.B setfsgid
is Linux specific and should not be used in programs intended to be portable.
.SH BUGS
No error messages of any kind are returned to the caller. At the very
least,
.B EPERM
should be returned when the call fails.
.SH "SEE ALSO"
.BR setfsuid (2)
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