thanks for  your reply,
  When  I  set the debug  mode  and  run  "libguestfs-test-tool"  the  result  is:
  virtTest@06MYRC5:~$ libguestfs-test-tool 
************************************************************
* IMPORTANT NOTICE
*
* When reporting bugs, include the COMPLETE, UNEDITED
* output below in your bug report.
*
************************************************************
libguestfs: trace: set_verbose true
libguestfs: trace: set_verbose = 0
libguestfs: trace: set_verbose true
libguestfs: trace: set_verbose = 0
LIBGUESTFS_DEBUG=1
LIBGUESTFS_TRACE=1
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games
SELinux: sh: 1: getenforce: not found
libguestfs: trace: add_drive_scratch 104857600
libguestfs: trace: get_tmpdir
libguestfs: trace: get_tmpdir = "/tmp"
libguestfs: trace: add_drive "/tmp/libguestfsIyeuW7/scratch.1" "format:raw" "cachemode:unsafe"
libguestfs: trace: add_drive = 0
libguestfs: trace: add_drive_scratch = 0
libguestfs: trace: get_append
libguestfs: trace: get_append = "NULL"
guestfs_get_append: (null)
libguestfs: trace: get_backend
libguestfs: trace: get_backend = "direct"
guestfs_get_backend: direct
libguestfs: trace: get_autosync
libguestfs: trace: get_autosync = 1
guestfs_get_autosync: 1
libguestfs: trace: get_cachedir
libguestfs: trace: get_cachedir = "/var/tmp"
guestfs_get_cachedir: /var/tmp
libguestfs: trace: get_direct
libguestfs: trace: get_direct = 0
guestfs_get_direct: 0
libguestfs: trace: get_hv
libguestfs: trace: get_hv = "/usr/bin/qemu-system-x86_64"
guestfs_get_hv: /usr/bin/qemu-system-x86_64
libguestfs: trace: get_memsize
libguestfs: trace: get_memsize = 500
guestfs_get_memsize: 500
libguestfs: trace: get_network
libguestfs: trace: get_network = 0
guestfs_get_network: 0
libguestfs: trace: get_path
libguestfs: trace: get_path = "/usr/lib/guestfs"
guestfs_get_path: /usr/lib/guestfs
libguestfs: trace: get_pgroup
libguestfs: trace: get_pgroup = 0
guestfs_get_pgroup: 0
libguestfs: trace: get_program
libguestfs: trace: get_program = "libguestfs-test-tool"
guestfs_get_program: libguestfs-test-tool
libguestfs: trace: get_recovery_proc
libguestfs: trace: get_recovery_proc = 1
guestfs_get_recovery_proc: 1
libguestfs: trace: get_selinux
libguestfs: trace: get_selinux = 0
guestfs_get_selinux: 0
libguestfs: trace: get_smp
libguestfs: trace: get_smp = 1
guestfs_get_smp: 1
libguestfs: trace: get_tmpdir
libguestfs: trace: get_tmpdir = "/tmp"
guestfs_get_tmpdir: /tmp
libguestfs: trace: get_trace
libguestfs: trace: get_trace = 1
guestfs_get_trace: 1
libguestfs: trace: get_verbose
libguestfs: trace: get_verbose = 1
guestfs_get_verbose: 1
host_cpu: x86_64
Launching appliance, timeout set to 600 seconds.
libguestfs: trace: launch
libguestfs: trace: version
libguestfs: trace: version = <struct guestfs_version *>
libguestfs: trace: get_backend
libguestfs: trace: get_backend = "direct"
libguestfs: launch: program=libguestfs-test-tool
libguestfs: launch: version=1.24.5
libguestfs: launch: backend registered: unix
libguestfs: launch: backend registered: uml
libguestfs: launch: backend registered: libvirt
libguestfs: launch: backend registered: direct
libguestfs: launch: backend=direct
libguestfs: launch: tmpdir=/tmp/libguestfsIyeuW7
libguestfs: launch: umask=0002
libguestfs: launch: euid=1000
libguestfs: command: run: /usr/bin/supermin-helper
libguestfs: command: run: \ --verbose
libguestfs: command: run: \ -f checksum
libguestfs: command: run: \ --host-cpu x86_64
libguestfs: command: run: \ /usr/lib/guestfs/supermin.d
supermin helper [00000ms] whitelist = (not specified)
supermin helper [00000ms] host_cpu = x86_64
supermin helper [00000ms] dtb_wildcard = (not specified)
supermin helper [00000ms] inputs:
supermin helper [00000ms] inputs[0] = /usr/lib/guestfs/supermin.d
supermin helper [00000ms] outputs:
supermin helper [00000ms] kernel = (none)
supermin helper [00000ms] dtb = (none)
supermin helper [00000ms] initrd = (none)
supermin helper [00000ms] appliance = (none)
libguestfs: checksum of existing appliance:
libguestfs: warning: supermin-helper -f checksum returned a short string
libguestfs: error: cannot find any suitable libguestfs supermin, fixed or old-style appliance on LIBGUESTFS_PATH (search path: /usr/lib/guestfs)
libguestfs: trace: launch = -1 (error)
libguestfs-test-tool: failed to launch appliance
libguestfs: trace: close
libguestfs: closing guestfs handle 0x6ac130 (state 0)
libguestfs: command: run: rm
libguestfs: command: run: \ -rf /tmp/libguestfsIyeuW7

when  I  run  " virt-df -d `virsh  domuuid  5`“  ，  the  result  is :

virtTest@06MYRC5:~$ virt-df -d `virsh domuuid 5`
libguestfs: trace: set_verbose true
libguestfs: trace: set_verbose = 0
libguestfs: create: flags = 0, handle = 0x15ee130, program = virt-df
libguestfs: trace: add_domain "572e2069-1d61-4e0a-9a7d-fc9e726c22cb" "readonly:true" "allowuuid:true" "readonlydisk:read"
libguestfs: opening libvirt handle: URI = NULL, auth = virConnectAuthPtrDefault, flags = 1
libguestfs: successfully opened libvirt handle: conn = 0x15ee5c0
libguestfs: trace: internal_set_libvirt_selinux_norelabel_disks false
libguestfs: trace: internal_set_libvirt_selinux_norelabel_disks = 0
libguestfs: disk[0]: filename: /var/lib/nova/instances/572e2069-1d61-4e0a-9a7d-fc9e726c22cb/disk
libguestfs: trace: add_drive "/var/lib/nova/instances/572e2069-1d61-4e0a-9a7d-fc9e726c22cb/disk" "readonly:true" "format:qcow2"
libguestfs: trace: add_drive = 0
libguestfs: trace: add_domain = 1
libguestfs: trace: launch
libguestfs: trace: get_tmpdir
libguestfs: trace: get_tmpdir = "/tmp"
libguestfs: trace: version
libguestfs: trace: version = <struct guestfs_version *>
libguestfs: trace: get_backend
libguestfs: trace: get_backend = "direct"
libguestfs: launch: program=virt-df
libguestfs: launch: version=1.24.5
libguestfs: launch: backend registered: unix
libguestfs: launch: backend registered: uml
libguestfs: launch: backend registered: libvirt
libguestfs: launch: backend registered: direct
libguestfs: launch: backend=direct
libguestfs: launch: tmpdir=/tmp/libguestfsLdtNb8
libguestfs: launch: umask=0002
libguestfs: launch: euid=1000
libguestfs: command: run: /usr/bin/supermin-helper
libguestfs: command: run: \ --verbose
libguestfs: command: run: \ -f checksum
libguestfs: command: run: \ --host-cpu x86_64
libguestfs: command: run: \ /usr/lib/guestfs/supermin.d
supermin helper [00000ms] whitelist = (not specified)
supermin helper [00000ms] host_cpu = x86_64
supermin helper [00000ms] dtb_wildcard = (not specified)
supermin helper [00000ms] inputs:
supermin helper [00000ms] inputs[0] = /usr/lib/guestfs/supermin.d
supermin helper [00000ms] outputs:
supermin helper [00000ms] kernel = (none)
supermin helper [00000ms] dtb = (none)
supermin helper [00000ms] initrd = (none)
supermin helper [00000ms] appliance = (none)
libguestfs: checksum of existing appliance:
libguestfs: warning: supermin-helper -f checksum returned a short string
libguestfs: error: cannot find any suitable libguestfs supermin, fixed or old-style appliance on LIBGUESTFS_PATH (search path: /usr/lib/guestfs)
libguestfs: trace: launch = -1 (error)
libguestfs: trace: close
libguestfs: closing guestfs handle 0x15ee130 (state 0)
libguestfs: command: run: rm
libguestfs: command: run: \ -rf /tmp/libguestfsLdtNb8



  


 
From: Richard W.M. Jones
Date: 2014-12-04 18:02
To: cuimingwen@incito.com.cn
CC: libguestfs
Subject: Re: virt-df error, help
On Thu, Dec 04, 2014 at 04:53:21PM +0800, cuimingwen@incito.com.cn wrote:
>  Hello，  Richard，
>     I run command  as   example： " virt-df -d `virsh  domuuid  5`"
>     some  errors  show :
>     libguestfs: warning: supermin-helper -f checksum returned a short string
>     libguestfs: error: cannot find any suitable libguestfs supermin, fixed or old-style appliance on LIBGUESTFS_PATH (search path: /usr/lib/guestfs)
>
> when  I  run  this command  as root ,  the  result  is  correct ,
> but  I  must  run  the command  as  not-root,  so  ,  how  can  I  do  ?,  please  help , thanks!
 
Enable debugging:
 
  http://libguestfs.org/guestfs-faq.1.html#debugging-libguestfs
 
Provide the complete output when debugging is enabled, sending it
to the mailing list (mailto:libguestfs@redhat.com)
 
Rich.
 
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/