add attach command

[ningmingxiao]

Signed-off-by: ningmingxiao ning.mingxiao@zte.com.cn

[AkihiroSuda]

Thanks, but this needs tests.

Also, I guess we don't support attaching multiple terminals to a single container and we have to document that.

[ningmingxiao]

I use nerdctl run a container and then nerdctl attach it,it will not work.
but use crictl run a container then nerdctl attach it will work

[AkihiroSuda]

I use nerdctl run a container and then nerdctl attach it,it will not work. but use crictl run a container then nerdctl attach it will work

Please document that in README.md and nerdctl attach --help

[fahedouch]

@ningmingxiao are you planning to continue working on his PR ?

[ningmingxiao]

@ningmingxiao are you planning to continue working ont his PR ?

when i use nerdctl run a container then i use nerdctl attach it, but it will not work, but if i use crictl run a container then nerdctl attach will work well, so i can't wirte testcase ,do you have some advices? @fahedouch @AkihiroSuda

[junnplus]

nerdctl run -d different from crictl/ctr tools, IO sets of task is a log URI. see https://github.com/containerd/nerdctl/blob/master/pkg/taskutil/taskutil.go#L54-L60

[AkihiroSuda]

Closing, as we merged #2108