feat(run): allow -i and -d together when -t is set

[mayur-tolexo]

Fixes #317

nerdctl run rejected -i together with -d via a hardcoded FIXME, so the command in #317 (nerdctl run -t -d -i ...) failed.

What this does

• Allows -i -d when -t is also set — with a TTY the containerd shim holds the pty open, so the detached container keeps a usable stdin and stays running. Unblocks the issue's exact command.
• Without -t, returns a clear error (flags -i and -d can only be specified together with -t) instead of the FIXME.

Why not non-TTY -d -i?

nerdctl is daemonless. For a detached container, stdout/stderr use containerd binary logging; the shim's createIO picks the IO path solely from the stdout URI scheme, so a binary:// logger and a stdin FIFO can't coexist. With no daemon to hold a plain stdin pipe open, a non-TTY -d -i process reads EOF immediately. Docker supports it only because dockerd holds the FIFOs; doing so in nerdctl would need a persistent per-container IO holder (conmon-style), out of scope here.

Out of scope

• run/create only — the same FIXME in exec/compose run is left alone.
• Attaching to an already-detached TTY container is a separate pre-existing limitation (TerminalBinaryIO stores a binary:// stdout that attach can't reopen).

Tests

New cmd/nerdctl/container/container_run_detach_interactive_linux_test.go:

• TestRunDetachInteractiveWithTTY — run -t -d -i runs detached and stays running.
• TestRunDetachInteractiveWithoutTTYFails — run -d -i (no -t) fails with the clear error (nerdctl-only; Docker supports it).

Verified locally in a Linux + containerd sandbox: gofmt, go vet, build, and the new + existing TestAttach* integration tests pass.

cc @AkihiroSuda

[mayur-tolexo]

Local test results

Run in a Linux + containerd dev sandbox (Docker --privileged, overlayfs snapshotter on an ext4-backed /var/lib/containerd).

Environment

• containerd 1.7.24
• runc 1.1.15
• go 1.26.4

Static checks

• gofmt -l on changed files: clean
• go vet ./pkg/cmd/container/ ./cmd/nerdctl/container/: clean
• go build ./cmd/nerdctl: ok

New tests — go test ./cmd/nerdctl/container/ -run TestRunDetachInteractive -test.target=nerdctl

--- PASS: TestRunDetachInteractiveWithoutTTYFails (0.04s)
--- PASS: TestRunDetachInteractiveWithTTY (0.35s)
ok  	github.com/containerd/nerdctl/v2/cmd/nerdctl/container	0.362s

Regression — existing attach suite -run TestAttach

--- PASS: TestAttachForAutoRemovedContainer (0.43s)
--- PASS: TestAttachDetachKeys (1.34s)
--- PASS: TestAttach (1.36s)
--- PASS: TestAttachNoStdin (5.36s)
ok  	github.com/containerd/nerdctl/v2/cmd/nerdctl/container	5.379s

Manual flag matrix also verified: run -d, run -t -d, run -t -d -i all start and stay running; run -d -i (no -t) fails with flags -i and -d can only be specified together with -t.

[mayur-tolexo]

Manually verified flag matrix

nerdctl run <flags> alpine <cmd> then inspect --format {{.State.Running}} (cmd = sleep 60, except the -i -d row uses cat):

flags	exit code	container state	notes
-d	0	running	unchanged
-t -d	0	running	unchanged
-t -d -i	0	running	enabled by this PR (issue #317 command)
-t -i -d	0	running	order-independent
-i -d (no -t)	1	(not created)	errors: flags -i and -d can only be specified together with -t

[Copilot]

Pull request overview

This PR updates nerdctl run/create flag validation to allow -i (interactive) and -d (detach) to be used together only when -t (TTY) is also set, addressing Issue #317 by removing the previous hardcoded FIXME rejection and replacing it with a clearer, behavior-based constraint.

Changes:

• Allow -i -d when -t is enabled (TTY case).
• Reject non-TTY -i -d with a clear error message explaining the constraint.
• Add Linux integration tests covering both the allowed (-t -d -i) and rejected (-d -i without -t) cases.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pkg/cmd/container/create.go	Replaces the old FIXME hard-fail with a conditional validation that only rejects -i -d when -t is not set, and improves the error message.
cmd/nerdctl/container/container_run_detach_interactive_linux_test.go	Adds integration tests to ensure run -t -d -i works and run -d -i fails with the expected error.

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[AkihiroSuda]

Please squash the commits

[AkihiroSuda]

Thanks