must not be on the same mount as the current root.
.IP \-
\fIput_old\fP must be at or underneath \fInew_root\fP;
-that is, adding a nonnegative
-number of \fI/..\fP to the string pointed to by \fIput_old\fP must yield
-the same directory as \fInew_root\fP.
+that is, adding some nonnegative
+number of "\fI/..\fP" prefixes to the pathname pointed to by
+.I put_old
+must yield the same directory as \fInew_root\fP.
.IP \-
.I new_root
must be a path to a mount point, but can't be
new root frees the old root directory of users,
allowing the old root mount to be unmounted more easily.)
.PP
-A typical use of
+One use of
.BR pivot_root ()
is during system startup, when the
-system mounts a temporary root filesystem (e.g., an \fBinitrd\fP), then
-mounts the real root filesystem, and eventually turns the latter into
-the current root of all relevant processes or threads.
+system mounts a temporary root filesystem (e.g., an
+.BR initrd (4)),
+then mounts the real root filesystem, and eventually turns the latter into
+the root directory of all relevant processes and threads.
A modern use is to set up a root filesystem during
the creation of a container.
.PP
modifies process root and current working directories in the
manner noted in DESCRIPTION
is necessary in order to prevent kernel threads from keeping the old
-root directory busy with their root and current working directory,
+root mount busy with their root and current working directories,
even if they never access
the filesystem in any way.
.PP