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333 lines
12 KiB
ReStructuredText
333 lines
12 KiB
ReStructuredText
.. role:: since
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=================
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Secret XML format
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=================
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.. contents::
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Secret XML
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----------
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Secrets stored by libvirt may have attributes associated with them, using the
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``secret`` element. The ``secret`` element has two optional attributes, each
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with values '``yes``' and '``no``', and defaulting to '``no``':
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``ephemeral``
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This secret must only be kept in memory, never stored persistently.
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``private``
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The value of the secret must not be revealed to any caller of libvirt, nor to
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any other node.
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The top-level ``secret`` element may contain the following elements:
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``uuid``
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An unique identifier for this secret (not necessarily in the UUID format). If
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omitted when defining a new secret, a random UUID is generated.
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``description``
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A human-readable description of the purpose of the secret.
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``usage``
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Specifies what this secret is used for. A mandatory ``type`` attribute
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specifies the usage category, currently only ``volume``, ``ceph``, ``iscsi``,
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``tls``, and ``vtpm`` are defined. Specific usage categories are described
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below.
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Usage type "volume"
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~~~~~~~~~~~~~~~~~~~
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This secret is associated with a volume, whether the format is either for a
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"luks" encrypted volume. Each volume will have a unique secret associated with
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it and it is safe to delete the secret after the volume is deleted. The
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``<usage type='volume'>`` element must contain a single ``volume`` element that
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specifies the path of the volume this secret is associated with. For example,
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create a volume-secret.xml file as follows:
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::
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<secret ephemeral='no' private='yes'>
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<description>Super secret name of my first puppy</description>
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<uuid>0a81f5b2-8403-7b23-c8d6-21ccc2f80d6f</uuid>
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<usage type='volume'>
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<volume>/var/lib/libvirt/images/puppyname.img</volume>
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</usage>
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</secret>
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Define the secret and set the passphrase as follows:
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::
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# virsh secret-define volume-secret.xml
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Secret 0a81f5b2-8403-7b23-c8d6-21ccc2f80d6f created
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See `Setting secret values in virsh`_ on how to set the value of the secret
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using ``virsh secret-set-value``.
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The volume type secret can be supplied either in volume XML during creation of a
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`storage volume <formatstorage.html#storage-volume-xml>`__ in order to provide
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the passphrase to encrypt the volume or in domain XML
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`disk device <formatdomain.html#hard-drives-floppy-disks-cdroms>`__ in order to provide the
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passphrase to decrypt the volume, :since:`since 2.1.0`. An example follows:
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::
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# cat luks-secret.xml
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<secret ephemeral='no' private='yes'>
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<description>LUKS Sample Secret</description>
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<uuid>f52a81b2-424e-490c-823d-6bd4235bc57</uuid>
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<usage type='volume'>
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<volume>/var/lib/libvirt/images/luks-sample.img</volume>
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</usage>
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</secret>
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# virsh secret-define luks-secret.xml
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Secret f52a81b2-424e-490c-823d-6bd4235bc57 created
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See `Setting secret values in virsh`_ on how to set the value of the secret
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using ``virsh secret-set-value``.
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The volume type secret can be supplied in domain XML for a luks storage volume
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`encryption <formatstorageencryption.html>`__ as follows:
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::
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<encryption format='luks'>
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<secret type='passphrase' uuid='f52a81b2-424e-490c-823d-6bd4235bc57'/>
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</encryption>
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Usage type "ceph"
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~~~~~~~~~~~~~~~~~
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This secret is associated with a Ceph RBD (rados block device). The
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``<usage type='ceph'>`` element must contain a single ``name`` element that
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specifies a usage name for the secret. The Ceph secret can then be used by UUID
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or by this usage name via the ``<auth>`` element of a `disk
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device <formatdomain.html#hard-drives-floppy-disks-cdroms>`__ or a `storage pool
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(rbd) <formatstorage.html>`__. :since:`Since 0.9.7`. The following is an
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example of the steps to be taken. First create a ceph-secret.xml file:
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::
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<secret ephemeral='no' private='yes'>
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<description>CEPH passphrase example</description>
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<usage type='ceph'>
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<name>ceph_example</name>
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</usage>
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</secret>
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Next, use ``virsh secret-define ceph-secret.xml`` to define the secret and
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``virsh secret-set-value`` using the generated UUID value and a base64 generated
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secret value in order to define the chosen secret pass phrase.
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::
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# virsh secret-define ceph-secret.xml
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Secret 1b40a534-8301-45d5-b1aa-11894ebb1735 created
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#
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# virsh secret-list
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UUID Usage
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-----------------------------------------------------------
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1b40a534-8301-45d5-b1aa-11894ebb1735 cephx ceph_example
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See `Setting secret values in virsh`_ on how to set the value of the secret
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using ``virsh secret-set-value``.
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The ceph secret can then be used by UUID or by the usage name via the ``<auth>``
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element in a domain's `<disk> <formatdomain.html#hard-drives-floppy-disks-cdroms>`__ element as
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follows:
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::
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<auth username='myname'>
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<secret type='ceph' usage='ceph_example'/>
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</auth>
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As well as the ``<auth>`` element in a `storage pool
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(rbd) <formatstorage.html>`__ ``<source>`` element as follows:
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::
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<auth type='ceph' username='myname'>
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<secret usage='ceph_example'/>
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</auth>
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Usage type "iscsi"
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~~~~~~~~~~~~~~~~~~
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This secret is associated with an iSCSI target for CHAP authentication. The
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``<usage type='iscsi'>`` element must contain a single ``target`` element that
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specifies a usage name for the secret. The iSCSI secret can then be used by UUID
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or by this usage name via the ``<auth>`` element of a `disk
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device <formatdomain.html#hard-drives-floppy-disks-cdroms>`__ or a `storage pool
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(iscsi) <formatstorage.html>`__. :since:`Since 1.0.4`. The following is an
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example of the XML that may be used to generate a secret for iSCSI CHAP
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authentication. Assume the following sample entry in an iSCSI authentication
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file:
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::
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<target iqn.2013-07.com.example:iscsi-pool>
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backing-store /home/tgtd/iscsi-pool/disk1
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backing-store /home/tgtd/iscsi-pool/disk2
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incominguser myname mysecret
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</target>
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Define an iscsi-secret.xml file to describe the secret. Use the ``incominguser``
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username used in your iSCSI authentication configuration file as the value for
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the ``username`` attribute. The ``description`` attribute should contain
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configuration specific data. The ``target`` name may be any name of your
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choosing to be used as the ``usage`` when used in the pool or disk XML
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description.
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::
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<secret ephemeral='no' private='yes'>
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<description>Passphrase for the iSCSI example.com server</description>
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<usage type='iscsi'>
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<target>libvirtiscsi</target>
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</usage>
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</secret>
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Next, use ``virsh secret-define iscsi-secret.xml`` to define the secret and
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``virsh secret-set-value`` using the generated UUID value and a base64 generated
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secret value in order to define the chosen secret pass phrase. The pass phrase
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must match the password used in the iSCSI authentication configuration file.
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::
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# virsh secret-define secret.xml
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Secret c4dbe20b-b1a3-4ac1-b6e6-2ac97852ebb6 created
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# virsh secret-list
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UUID Usage
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-----------------------------------------------------------
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c4dbe20b-b1a3-4ac1-b6e6-2ac97852ebb6 iscsi libvirtiscsi
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See `Setting secret values in virsh`_ on how to set the value of the secret
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using ``virsh secret-set-value``.
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The iSCSI secret can then be used by UUID or by the usage name via the
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``<auth>`` element in a domain's `<disk> <formatdomain.html#hard-drives-floppy-disks-cdroms>`__
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element as follows:
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::
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<auth username='myname'>
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<secret type='iscsi' usage='libvirtiscsi'/>
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</auth>
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As well as the ``<auth>`` element in a `storage pool
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(iscsi) <formatstorage.html>`__ ``<source>`` element as follows:
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::
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<auth type='chap' username='myname'>
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<secret usage='libvirtiscsi'/>
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</auth>
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Usage type "tls"
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~~~~~~~~~~~~~~~~
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This secret may be used in order to provide the passphrase for the private key
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used to provide TLS credentials. The ``<usage type='tls'>`` element must contain
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a single ``name`` element that specifies a usage name for the secret.
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:since:`Since 2.3.0`. The following is an example of the expected XML and
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processing to define the secret:
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::
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# cat tls-secret.xml
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<secret ephemeral='no' private='yes'>
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<description>sample tls secret</description>
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<usage type='tls'>
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<name>TLS_example</name>
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</usage>
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</secret>
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# virsh secret-define tls-secret.xml
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Secret 718c71bd-67b5-4a2b-87ec-a24e8ca200dc created
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# virsh secret-list
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UUID Usage
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-----------------------------------------------------------
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718c71bd-67b5-4a2b-87ec-a24e8ca200dc tls TLS_example
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A secret may also be defined via the
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`virSecretDefineXML <html/libvirt-libvirt-secret.html#virSecretDefineXML>`__
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API. Once the secret is defined, a secret value will need to be set. The secret
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would be the passphrase used to access the TLS credentials. The following is a
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simple example of using ``virsh secret-set-value`` to set the secret value. The
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`virSecretSetValue <html/libvirt-libvirt-secret.html#virSecretSetValue>`__ API
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may also be used to set a more secure secret without using printable/readable
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characters.
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Usage type "vtpm"
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~~~~~~~~~~~~~~~~~
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This secret is associated with a virtualized TPM (vTPM) and serves as a
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passphrase for deriving a key from for encrypting the state of the vTPM. The
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``<usage type='vtpm'>`` element must contain a single ``name`` element that
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specifies a usage name for the secret. The vTPM secret can then be used by UUID
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via the ``<encryption>`` element of a `tpm <formatdomain.html#tpm-device>`__
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when using an emulator. :since:`Since 5.6.0`. The following is an example of
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the steps to be taken. First create a vtpm-secret.xml file:
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::
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# cat vtpm-secret.xml
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<secret ephemeral='no' private='yes'>
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<description>sample vTPM secret</description>
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<usage type='vtpm'>
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<name>VTPM_example</name>
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</usage>
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</secret>
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# virsh secret-define vtpm-secret.xml
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Secret 6dd3e4a5-1d76-44ce-961f-f119f5aad935 created
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# virsh secret-list
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UUID Usage
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----------------------------------------------------------------------------------------
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6dd3e4a5-1d76-44ce-961f-f119f5aad935 vtpm VTPM_example
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A secret may also be defined via the
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`virSecretDefineXML <html/libvirt-libvirt-secret.html#virSecretDefineXML>`__
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API. Once the secret is defined, a secret value will need to be set. The secret
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would be the passphrase used to decrypt the vTPM state. The following is a
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simple example of using ``virsh secret-set-value`` to set the secret value. The
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`virSecretSetValue <html/libvirt-libvirt-secret.html#virSecretSetValue>`__ API
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may also be used to set a more secure secret without using printable/readable
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characters.
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Setting secret values in virsh
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------------------------------
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To set the value of the secret you can use the following virsh commands. If the
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secret is a password-like string (printable characters, no newline) you can use:
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::
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# virsh secret-set-value --interactive 6dd3e4a5-1d76-44ce-961f-f119f5aad935
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Enter new value for secret:
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Secret value set
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Another secure option is to read the secret from a file. This way the secret can
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contain any bytes (even NUL and non-printable characters). The length of the
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secret is the length of the input file. Alternatively the ``--plain`` option can
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be omitted if the file contents are base64-encoded.
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::
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# virsh secret-set-value 6dd3e4a5-1d76-44ce-961f-f119f5aad935 --file --plain secretinfile
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Secret value set
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**WARNING** The following approach is **insecure** and deprecated. The secret
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can also be set via an argument. Note that other users may see the actual secret
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in the process listing! The secret must be base64 encoded.
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::
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# MYSECRET=`printf %s "open sesame" | base64`
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# virsh secret-set-value 6dd3e4a5-1d76-44ce-961f-f119f5aad935 $MYSECRET
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Secret value set
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