[RHEL 8] Use of qemu-img info -U option to avoid locking error

Solution In Progress - Updated -

Issue

  • How do I get disk information from a live guest

  • libguestfs tools are failing to get shared "write" lock on running KVM guests

    # virt-df -d rhel-7
    libguestfs: error: could not create appliance through libvirt.
    
    Try running qemu directly without libvirt using this environment variable:
    export LIBGUESTFS_BACKEND=direct
    
    Original error from libvirt: internal error: process exited while connecting to monitor: arserial0,id=serial0 -chardev socket,id=charchannel0,path=/tmp/libguestfsMAjZPC/guestfsd.sock -device  virtserialport,bus=virtio-serial0.0,nr=1,chardev=charchannel0,id=channel0,name=org.libguestfs.channel.0 -object rng-random,id=objrng0,filename=/dev/urandom -device virtio-rng-pci,rng=objrng0,id=rng0,bus=pci.0,addr=0x4 -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny -msg timestamp=on
    2020-03-03 17:29:46.520+0000: Domain id=3 is tainted: custom-argv
    2020-03-03 17:29:46.520+0000: Domain id=3 is tainted: host-cpu
    2020-03-03T17:29:46.590130Z qemu-kvm: -drive file=/tmp/libguestfsCUcrvw/overlay1.qcow2,format=qcow2,if=none,id=drive-scsi0-0-0-0,cache=unsafe: Could not open backing file: Failed to get shared "write" lock
    Is another process using the image [/home/qemu/rhel-server-7.7-x86_64-kvm.qcow2]? [code=1 int1=-1]
    

Environment

  • RHEL 8
  • libguestfs-1.38.4-14

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