# Permission denied using QEMU 'blockdev-add'

**URL:** <https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561>\
**Category:** Product Support\
**Created:** [May 17, 2022, 1:04pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561 "2022-05-17T13:04:26Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![gbernardes](https://avatars.discourse-cdn.com/v4/letter/g/c67d28/32.png) [@gbernardes](https://forum.opennebula.io/u/gbernardes)\
**Post date:** [May 17, 2022, 1:04pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561/1 "2022-05-17T13:04:26Z")

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Hi,

I want to use [virtnbdbackup](https://github.com/abbbi/virtnbdbackup/) to make backup of VMs that use Qcow format, but I had this error when I try it:

```
libvirt.libvirtError: internal error: unable to execute QEMU command 'blockdev-add': Could not open '/var/tmp/backup.6LZFF.vda': Permission denied

```

Exists any limitations to using this ‘blockdev-add’?

Using:

- Rocky Linux (Debian 11 the same error)
- Opennebula-host-kvm package
- Opennebula 6.4

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**Author:** ![atodorov\_storpool](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.opennebula.io/atodorov_storpool/32/5327_2.png) [@atodorov\_storpool](https://forum.opennebula.io/u/atodorov_storpool)\
**Post date:** [May 17, 2022, 1:15pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561/2 "2022-05-17T13:15:15Z")

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Hi,  
A wild guess - the qemu process is started as _oneadmin_ user. Did you try running the script as oneadmin?

BR,  
Anton Todorov

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<div class="post-metadata">

**Author:** ![gbernardes](https://avatars.discourse-cdn.com/v4/letter/g/c67d28/32.png) [@gbernardes](https://forum.opennebula.io/u/gbernardes)\
**Post date:** [May 17, 2022, 1:25pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561/3 "2022-05-17T13:25:44Z")

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Yes I tried, but has the same error ☹

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<div class="post-metadata">

**Author:** ![atodorov\_storpool](https://yyz1.discourse-cdn.com/flex031/user_avatar/forum.opennebula.io/atodorov_storpool/32/5327_2.png) [@atodorov\_storpool](https://forum.opennebula.io/u/atodorov_storpool)\
**Post date:** [May 17, 2022, 1:29pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561/4 "2022-05-17T13:29:36Z")

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Then you should check is debugging available debug in the backup tool to figure-out why qemu-kvm has no permissions to access the file in the given path…

BR,  
Anton Todorov

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<div class="post-metadata">

**Author:** ![gbernardes](https://avatars.discourse-cdn.com/v4/letter/g/c67d28/32.png) [@gbernardes](https://forum.opennebula.io/u/gbernardes)\
**Post date:** [May 18, 2022, 5:37pm UTC](https://forum.opennebula.io/t/permission-denied-using-qemu-blockdev-add/10561/5 "2022-05-18T17:37:05Z")

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Hi, I found the problem: in /etc/libvirt/qemu.conf, the option “dynamic\_ownership = 0” (included in opennebula-node-kvm) makes the scratch file is created with “root” user and permission 600; then generate error “permission denied”.

Setting “dynamic\_ownership = 1” solving the backup problem, but what problem could it bring to Opennebula?