09-18-2002
On my HP-UX systems, I see that /dev/null is owned by bin. This means that either bin or root could change the mode. I would chown /dev/null to root and let it change modes again. If it does, you know the process was a root process.
Make sure that no one is signed on as root or su'ed to root. If it changes, either a running process or a cronjob did it.
"ls -lc /dev/root" will get the exact time of change. Check every cron job that was running during the change. The periodic nature of the problem also is pointing to a bad cron job.
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LEARN ABOUT XFREE86
pivot_root
PIVOT_ROOT(8) System Administration PIVOT_ROOT(8)
NAME
pivot_root - change the root filesystem
SYNOPSIS
pivot_root new_root put_old
DESCRIPTION
pivot_root moves the root file system of the current process to the directory put_old and makes new_root the new root file system. Since
pivot_root(8) simply calls pivot_root(2), we refer to the man page of the latter for further details.
Note that, depending on the implementation of pivot_root, root and cwd of the caller may or may not change. The following is a sequence for
invoking pivot_root that works in either case, assuming that pivot_root and chroot are in the current PATH:
cd new_root
pivot_root . put_old
exec chroot . command
Note that chroot must be available under the old root and under the new root, because pivot_root may or may not have implicitly changed the
root directory of the shell.
Note that exec chroot changes the running executable, which is necessary if the old root directory should be unmounted afterwards. Also
note that standard input, output, and error may still point to a device on the old root file system, keeping it busy. They can easily be
changed when invoking chroot (see below; note the absence of leading slashes to make it work whether pivot_root has changed the shell's
root or not).
OPTIONS
-V, --version
Display version information and exit.
-h, --help
Display help text and exit.
EXAMPLES
Change the root file system to /dev/hda1 from an interactive shell:
mount /dev/hda1 /new-root
cd /new-root
pivot_root . old-root
exec chroot . sh <dev/console >dev/console 2>&1
umount /old-root
Mount the new root file system over NFS from 10.0.0.1:/my_root and run init:
ifconfig lo 127.0.0.1 up # for portmap
# configure Ethernet or such
portmap # for lockd (implicitly started by mount)
mount -o ro 10.0.0.1:/my_root /mnt
killall portmap # portmap keeps old root busy
cd /mnt
pivot_root . old_root
exec chroot . sh -c 'umount /old_root; exec /sbin/init'
<dev/console >dev/console 2>&1
SEE ALSO
chroot(1), pivot_root(2), mount(8), switch_root(8), umount(8)
AVAILABILITY
The pivot_root command is part of the util-linux package and is available from https://www.kernel.org/pub/linux/utils/util-linux/.
util-linux August 2011 PIVOT_ROOT(8)