Add documentation for additional reason why snapshot-revert might need
to be forced. This explains why restoring an inactive snapshot while
there is managed saved state is refused by default.

Signed-off-by: Michael Weiser <michael.weiser@gmx.de>
Cc: Cole Robinson <crobinso@redhat.com>
---
 docs/manpages/virsh.rst | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
index f5f962cba1..09be872fdf 100644
--- a/docs/manpages/virsh.rst
+++ b/docs/manpages/virsh.rst
@@ -6951,7 +6951,7 @@ no vm state leaves the domain in an inactive state.  Passing either the
 transient domains cannot be inactive, it is required to use one of these
 flags when reverting to a disk snapshot of a transient domain.
 
-There are two cases where a snapshot revert involves extra risk, which
+There are a number of cases where a snapshot revert involves extra risk, which
 requires the use of *--force* to proceed:
 
   * One is the case of a snapshot that lacks full domain information for
@@ -6961,7 +6961,7 @@ requires the use of *--force* to proceed:
     libvirt that the snapshot is compatible with the current configuration
     (and if it is not, the domain will likely fail to run).
 
-  * The other is the case of reverting from a running domain to an active
+  * Another is the case of reverting from a running domain to an active
     state where a new hypervisor has to be created rather than reusing the
     existing hypervisor, because it implies drawbacks such as breaking any
     existing VNC or Spice connections; this condition happens with an active
@@ -6969,6 +6969,13 @@ requires the use of *--force* to proceed:
     an inactive snapshot that is combined with the *--start* or *--pause*
     flag.
 
+  * Also, libvirt will refuse to restore snapshots of inactive qemu domains
+    while there is managed saved state. This is because those snapshots do not
+    contain memory state and will therefore not replace the exising memory
+    state. This ends up switching a disk underneath a running system and will
+    likely cause extensive filesystem corruption or crashes due to swap content
+    mismatches when run.
+
 
 snapshot-delete
 ---------------
-- 
2.24.1


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On 1/2/20 1:00 PM, Michael Weiser wrote:
> Add documentation for additional reason why snapshot-revert might need
> to be forced. This explains why restoring an inactive snapshot while
> there is managed saved state is refused by default.
> 
> Signed-off-by: Michael Weiser <michael.weiser@gmx.de>
> Cc: Cole Robinson <crobinso@redhat.com>
> ---
>   docs/manpages/virsh.rst | 11 +++++++++--
>   1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/docs/manpages/virsh.rst b/docs/manpages/virsh.rst
> index f5f962cba1..09be872fdf 100644
> --- a/docs/manpages/virsh.rst
> +++ b/docs/manpages/virsh.rst
> @@ -6951,7 +6951,7 @@ no vm state leaves the domain in an inactive state.  Passing either the
>   transient domains cannot be inactive, it is required to use one of these
>   flags when reverting to a disk snapshot of a transient domain.
>   
> -There are two cases where a snapshot revert involves extra risk, which
> +There are a number of cases where a snapshot revert involves extra risk, which
>   requires the use of *--force* to proceed:
>   
>     * One is the case of a snapshot that lacks full domain information for
> @@ -6961,7 +6961,7 @@ requires the use of *--force* to proceed:
>       libvirt that the snapshot is compatible with the current configuration
>       (and if it is not, the domain will likely fail to run).
>   
> -  * The other is the case of reverting from a running domain to an active
> +  * Another is the case of reverting from a running domain to an active
>       state where a new hypervisor has to be created rather than reusing the
>       existing hypervisor, because it implies drawbacks such as breaking any
>       existing VNC or Spice connections; this condition happens with an active
> @@ -6969,6 +6969,13 @@ requires the use of *--force* to proceed:
>       an inactive snapshot that is combined with the *--start* or *--pause*
>       flag.
>   
> +  * Also, libvirt will refuse to restore snapshots of inactive qemu domains


Side note: there is mixed usage of both 'qemu' and 'QEMU' in this documentation,
with more instances of 'QEMU'.


> +    while there is managed saved state. This is because those snapshots do not
> +    contain memory state and will therefore not replace the exising memory

s/exising/existing


With this typo fixed:


Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>



> +    state. This ends up switching a disk underneath a running system and will
> +    likely cause extensive filesystem corruption or crashes due to swap content
> +    mismatches when run.
> +
>   
>   snapshot-delete
>   ---------------
> 

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