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163 lines
3.6 KiB
Plaintext
163 lines
3.6 KiB
Plaintext
=head1 NAME
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guestunmount - Unmount a guestmounted filesystem
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=head1 SYNOPSIS
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guestunmount mountpoint
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guestunmount --fd=<FD> mountpoint
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=head1 DESCRIPTION
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guestunmount is a utility to clean up mounted filesystems
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automatically. L<guestmount(1)> mounts filesystems using libguestfs.
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This program unmounts the filesystem when a program or script has finished
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with it.
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guestunmount is a wrapper around the FUSE L<fusermount(1)> program,
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which must exist on the current C<PATH>.
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There are two ways to use guestunmount. When called as:
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guestunmount mountpoint
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it unmounts C<mountpoint> immediately.
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When called as:
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guestunmount --fd=FD mountpoint
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it waits until the pipe C<FD> is closed. This can be used to monitor
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another process and clean up its mountpoint when that process exits,
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as described below.
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=head2 FROM PROGRAMS
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You can just call C<guestunmount mountpoint> from the program, but a
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more sophisticated way to use guestunmount is to have it monitor your
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program so it can clean up the mount point if your program exits
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unexpectedly.
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In the program, create a pipe (eg. by calling L<pipe(2)>). Let C<FD>
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be the file descriptor number of the read side of the pipe
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(ie. C<pipefd[0]>).
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After mounting the filesystem with L<guestmount(1)> (on
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C<mountpoint>), fork and run guestunmount like this:
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guestunmount --fd=FD mountpoint
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Close the read side of the pipe in the parent process.
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Now, when the write side of the pipe (ie. C<pipefd[1]>) is closed for
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any reason, either explicitly or because the parent process
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exits, guestunmount notices and unmounts the mountpoint.
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If your operating system supports it, you should set the C<FD_CLOEXEC>
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flag on the write side of the pipe. This is so that other child
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processes don't inherit the file descriptor and keep it open.
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Guestunmount never daemonizes itself.
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=head2 FROM SHELL SCRIPTS
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Since bash doesn't provide a way to create an unnamed pipe, use a trap
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to call guestunmount on exit like this:
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trap "guestunmount mountpoint" EXIT INT QUIT TERM
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=head1 OPTIONS
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=over 4
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=item B<--fd=FD>
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Specify the pipe file descriptor to monitor, and delay cleanup until
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that pipe is closed.
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=item B<--help>
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Display brief help and exit.
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=item B<-q>
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=item B<--quiet>
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Don't display error messages from fusermount. The return status is
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still set (see L</EXIT STATUS> below).
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=item B<--no-retry>
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=item B<--retry=N>
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By default, guestunmount will retry the fusermount operation up to
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S<5 times> (that is, it will run it up to S<6 times> = S<1 try> +
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S<5 retries>).
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Use I<--no-retry> to make guestunmount run fusermount only once.
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Use I<--retry=N> to make guestunmount retry C<N> times instead of 5.
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guestunmount performs an exponential back-off between retries, waiting
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S<1 second>, S<2 seconds>, S<4 seconds>, etc before each retry.
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=item B<-V>
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=item B<--version>
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Display the program version and exit.
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=back
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=head1 ENVIRONMENT VARIABLES
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=over 4
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=item C<PATH>
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The L<fusermount(1)> program (supplied by FUSE) must be available on
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the current C<PATH>.
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=back
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=head1 EXIT STATUS
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This program returns 0 if successful, or one of the following error
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codes:
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=over 4
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=item C<1>
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Program error, eg. could not allocate memory, could not run fusermount.
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See the error message printed for more information.
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=item C<2>
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The mount point could not be unmounted even after retrying. See
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the error message printed for the underlying fusermount error.
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=item C<3>
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The mount point is not mounted.
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=back
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=head1 SEE ALSO
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L<guestmount(1)>,
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L<fusermount(1)>,
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L<pipe(2)>,
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L<guestfs(3)/MOUNT LOCAL>,
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L<http://libguestfs.org/>,
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L<http://fuse.sf.net/>.
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=head1 AUTHORS
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Richard W.M. Jones (C<rjones at redhat dot com>)
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=head1 COPYRIGHT
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Copyright (C) 2013 Red Hat Inc.
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