SETFSGID(2) Linux Programmer's Manual SETFSGID(2) NAME setfsgid - set group identity used for file system checks SYNOPSIS int setfsgid(uid_t fsgid) DESCRIPTION setfsgid sets the group ID that the Linux kernel uses to check for all accesses to the file system. Normally, the value of fsgid will shadow the value of the effective group ID. In fact, whenever the effective group ID is changed, fsgid will also be changed to new value of effec- tive group ID. An explicit call to setfsgid is usually only used by pro- grams such as the Linux NFS server that need to change what group ID is used for file access without a corre- sponding 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. setfsgid will only succeed if the caller is the superuser or if fsgid matches either the real group ID, effective group ID, saved group ID, or the current value of fsgid. RETURN VALUE On success, the previous value of fsgid is returned. On error, the current value of fsgid is returned. CONFORMING TO setfsgid is Linux specific and should not be used in pro- grams intended to be portable. BUGS No error messages of any kind are returned to the caller. At the very least, EPERM should be returned when the call fails. SEE ALSO setfsuid(2) Linux 1.3.15 6 August 1995 1