[libvirt] [PATCH] docs: Document NVRAM behavior on transient domains
Since 1.2.8 it's possible to use OVMF on domains. Moreover, it's possible to have libvirt create NVRAM file per domain. Later, when domain is undefined, the file is removed too. However, things are a bit complicated when domain's transient. There's no undefine to transient domains. There are two options: 1) leave the file behind and let mgmt app remove it. 2) remove it automatically as domain dies. But, in some scenarios mgmt app may want to preserve the file, copy it somewhere safe, and then copy it back when the domain is starting again. And this wouldn't be possible with case 2). So, even though case 1) leaves some files behind (possibly undeleted for a long time), the files themselves are small (128K each). And data loss is worse than full disk, isn't it? Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- docs/formatdomain.html.in | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index d4189e6..705d497 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -147,7 +147,10 @@ started up libvirt copies so called master NVRAM store file defined in <code>qemu.conf</code>. If needed, the <code>template</code> attribute can be used to per domain override map of master NVRAM stores - from the config file. <span class="since">Since 1.2.8</span></dd> + from the config file. Note, that for transient domains if the NVRAM file + has been created by libvirt it is left behind and it management + application's responsibility to save and remove file (if needed to be + persistent). <span class="since">Since 1.2.8</span></dd> <dt><code>boot</code></dt> <dd>The <code>dev</code> attribute takes one of the values "fd", "hd", "cdrom" or "network" and is used to specify the next boot device -- 2.0.4
On Tue, Nov 18, 2014 at 05:06:34PM +0100, Michal Privoznik wrote:
Since 1.2.8 it's possible to use OVMF on domains. Moreover, it's possible to have libvirt create NVRAM file per domain. Later, when domain is undefined, the file is removed too. However, things are a bit complicated when domain's transient. There's no undefine to transient domains. There are two options: 1) leave the file behind and let mgmt app remove it. 2) remove it automatically as domain dies. But, in some scenarios mgmt app may want to preserve the file, copy it somewhere safe, and then copy it back when the domain is starting again. And this wouldn't be possible with case 2). So, even though case 1) leaves some files behind (possibly undeleted for a long time), the files themselves are small (128K each). And data loss is worse than full disk, isn't it?
Just wondering, Does that mean that _if_ the management application relies on our remote driver (has no access) and wants to manage the file it has to create a pool type='dir' where the files are or something similar? It can then do vol-{up,down}load or vol-delete properly. And by default all the variable stores are by default in the same location (/var/lib/libvirt/nvram), so one pool for that makes perfect sense, am I right?
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- docs/formatdomain.html.in | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index d4189e6..705d497 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -147,7 +147,10 @@ started up libvirt copies so called master NVRAM store file defined in <code>qemu.conf</code>. If needed, the <code>template</code> attribute can be used to per domain override map of master NVRAM stores - from the config file. <span class="since">Since 1.2.8</span></dd> + from the config file. Note, that for transient domains if the NVRAM file + has been created by libvirt it is left behind and it management
s/it management/it is management/ ACK with the typo changed. Martin
On 19.11.2014 07:22, Martin Kletzander wrote:
On Tue, Nov 18, 2014 at 05:06:34PM +0100, Michal Privoznik wrote:
Since 1.2.8 it's possible to use OVMF on domains. Moreover, it's possible to have libvirt create NVRAM file per domain. Later, when domain is undefined, the file is removed too. However, things are a bit complicated when domain's transient. There's no undefine to transient domains. There are two options: 1) leave the file behind and let mgmt app remove it. 2) remove it automatically as domain dies. But, in some scenarios mgmt app may want to preserve the file, copy it somewhere safe, and then copy it back when the domain is starting again. And this wouldn't be possible with case 2). So, even though case 1) leaves some files behind (possibly undeleted for a long time), the files themselves are small (128K each). And data loss is worse than full disk, isn't it?
Just wondering, Does that mean that _if_ the management application relies on our remote driver (has no access) and wants to manage the file it has to create a pool type='dir' where the files are or something similar? It can then do vol-{up,down}load or vol-delete properly. And by default all the variable stores are by default in the same location (/var/lib/libvirt/nvram), so one pool for that makes perfect sense, am I right?
Yes, that's exactly how NVRAM files are to be manipulated using our storage APIs. Just note, that the path to NVRAM store is configurable in domain XML, so users may configure a different path to already existing dir pool. Then, when domain's starting up, libvirt will create the NVRAM file and copy the contents from central image into it.
Signed-off-by: Michal Privoznik <mprivozn@redhat.com> --- docs/formatdomain.html.in | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index d4189e6..705d497 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -147,7 +147,10 @@ started up libvirt copies so called master NVRAM store file defined in <code>qemu.conf</code>. If needed, the <code>template</code> attribute can be used to per domain override map of master NVRAM stores - from the config file. <span class="since">Since 1.2.8</span></dd> + from the config file. Note, that for transient domains if the NVRAM file + has been created by libvirt it is left behind and it management
s/it management/it is management/
ACK with the typo changed.
Martin
Ah, thanks for catching that. Fixed and pushed. Michal
participants (2)
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Martin Kletzander -
Michal Privoznik