12:33 p.m.
first, what is the difference between "podman pause" and "podman
stop", particularly since "man podman-pause" seems to confuse the two:
OPTIONS
--all, -a
Pause all running containers.
EXAMPLE
... snip ...
Pause all running containers.
podman stop -a
^^^^
so anyone reading "man podman-pause" is going to think that "stop" is
a synonym, at least reading that example.
in addition, "man podman-stop" doesn't help the situation by not
distinguishing between paused and stopped containers:
OPTIONS
--all, -a
Stop all running containers. This does not include paused con‐
tainers.
second issue:
$ podman pause musing_knuth
Error: pause is not supported for rootless containers
$
even if this is true, there is nothing in "man podman-pause" to
suggest that this might occur, which is definitely grounds for
confusion.
rday
9:41 a.m.
I'll give it a try, if Dan or Matt say differently, go with them.
`podman pause` pauses the processes in the container and puts the
container into the "Paused" state. You can kind of think of it as a
flash freeze of the container. The `podman unpause` command unpauses
the container and let's the processes continue running from the point
they were at when they were paused.
`podman stop` is a bigger hammer. It kills all the processes within the
container and puts the container into the "Exited" state. The container
can be restarted with `podman start` and all the processes in the
container will have to restart from scratch.
t
On 1/26/20 1:33 PM, Robert P. J. Day wrote:
first, what is the difference between "podman pause" and
"podman
stop", particularly since "man podman-pause" seems to confuse the two:
OPTIONS
--all, -a
Pause all running containers.
EXAMPLE
... snip ...
Pause all running containers.
podman stop -a
^^^^
so anyone reading "man podman-pause" is going to think that "stop"
is
a synonym, at least reading that example.
in addition, "man podman-stop" doesn't help the situation by not
distinguishing between paused and stopped containers:
OPTIONS
--all, -a
Stop all running containers. This does not include paused con‐
tainers.
second issue:
$ podman pause musing_knuth
Error: pause is not supported for rootless containers
$
even if this is true, there is nothing in "man podman-pause" to
suggest that this might occur, which is definitely grounds for
confusion.
rday
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9:56 a.m.
On Wed, 29 Jan 2020, Tom Sweeney wrote:
I'll give it a try, if Dan or Matt say differently, go with
them.
`podman pause` pauses the processes in the container and puts the
container into the "Paused" state. You can kind of think of it as a
flash freeze of the container. The `podman unpause` command
unpauses the container and let's the processes continue running from
the point they were at when they were paused.
`podman stop` is a bigger hammer. It kills all the processes within
the container and puts the container into the "Exited" state. The
container can be restarted with `podman start` and all the processes
in the container will have to restart from scratch.
after playing for a bit, i did figure out most of this ... the one
thing i *think* i verified and that would be worth putting in "man
podman-stop" is that the overlay read-write layer is discarded upon
stopping, so all changes during that session are thrown away (i
verified this with "podman inspect" and "python -m json.tool").
i think mentioning that (and also that one can still see the stopped
container with "podman container ls -a") would make things clearer.
rday
10:14 a.m.
On 2020-01-29 10:56, Robert P. J. Day wrote:
On Wed, 29 Jan 2020, Tom Sweeney wrote:
> I'll give it a try, if Dan or Matt say differently, go with them.
>
> `podman pause` pauses the processes in the container and puts the
> container into the "Paused" state. You can kind of think of it as a
> flash freeze of the container. The `podman unpause` command
> unpauses the container and let's the processes continue running from
> the point they were at when they were paused.
>
> `podman stop` is a bigger hammer. It kills all the processes within
> the container and puts the container into the "Exited" state. The
> container can be restarted with `podman start` and all the processes
> in the container will have to restart from scratch.
after playing for a bit, i did figure out most of this ... the one
thing i *think* i verified and that would be worth putting in "man
podman-stop" is that the overlay read-write layer is discarded upon
stopping, so all changes during that session are thrown away (i
verified this with "podman inspect" and "python -m json.tool").
That sounds wrong - we shouldn't discard container changes until it's
removed. If it's doing that, it's 100% a bug.
Pause uses the Freezer cgroup to keep the processes of a container
alive, but prevent them from executing. If you unpause, the container
keeps going from whatever point it was paused at. Stop breaks out
SIGTERM, and then SIGKILL if that fails, to cause all processes in the
container to exit. Pause will not move the container to Exited state
and set an exit code, Stop will do this.
Thanks,
Matt Heon
i think mentioning that (and also that one can still see the stopped
container with "podman container ls -a") would make things clearer.
rday
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10:20 a.m.
On Wed, 29 Jan 2020, Matt Heon wrote:
On 2020-01-29 10:56, Robert P. J. Day wrote:
>On Wed, 29 Jan 2020, Tom Sweeney wrote:
>
>> I'll give it a try, if Dan or Matt say differently, go with them.
>>
>> `podman pause` pauses the processes in the container and puts the
>> container into the "Paused" state. You can kind of think of it as a
>> flash freeze of the container. The `podman unpause` command
>> unpauses the container and let's the processes continue running from
>> the point they were at when they were paused.
>>
>> `podman stop` is a bigger hammer. It kills all the processes within
>> the container and puts the container into the "Exited" state. The
>> container can be restarted with `podman start` and all the processes
>> in the container will have to restart from scratch.
>
> after playing for a bit, i did figure out most of this ... the one
>thing i *think* i verified and that would be worth putting in "man
>podman-stop" is that the overlay read-write layer is discarded upon
>stopping, so all changes during that session are thrown away (i
>verified this with "podman inspect" and "python -m json.tool").
That sounds wrong - we shouldn't discard container changes until it's
removed. If it's doing that, it's 100% a bug.
hang on ... i may have misread what i was looking at, so ignore that
previous note.
sorry.
rday
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