Bug#469540: glibc-doc: Documentation of umount() and umount2() wrong

[Roland Stigge <stigge@antcom.de>]

Package: glibc-doc
Version: 2.7-9
Severity: normal

Hi,

the documentation of umount2() (and therefore, for umount() also) says:

"You can identify the filesystem to unmount either by the device special
file that contains the filesystem or by the mount point. The effect is
the same."

However, specifying the device special file doesn't work (while
specifying the mount point works fine).

Example:

myumount.c:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/mount.h>
#include <errno.h>
int main(int argc, char*argv[]) {
	int ret;

	ret = umount("/dev/sda1");
	printf("Return: %d, errno = %d\n", ret, errno);
	return 0;
}


Shell:
# cat /proc/mounts |grep sda1
/dev/sda1 /mnt/usbdisk vfat rw,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1 0 0
# ./myumount 
Return: -1, errno = 22
# cat /proc/mounts |grep sda1
/dev/sda1 /mnt/usbdisk vfat rw,fmask=0022,dmask=0022,codepage=cp437,iocharset=iso8859-1 0 0
#


I can reproduce this on different machines, with different device nodes
and kernels.


For the record, using the mount point works:
# ./myumount 
Return: 0, errno = 0
#


This is unrelated to MNT_FORCE.

Thanks for considering,

Roland

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: i386 (i686)

Kernel: Linux 2.6.24-rt1 (SMP w/1 CPU core; PREEMPT)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to en_GB.UTF-8)
Shell: /bin/sh linked to /bin/bash

-- debconf-show failed