vmlab exec

vmlab exec runs one command inside a guest through the vmlab agent and mirrors its standard output, standard error, and exit code. It rides the agent's virtio-serial channel, so it works on a machine with no guest network. A VM and a container answer the same request; `vmlab container exec` is the same verb under the container noun.

vmlab exec [OPTIONS] <VM> [-- <CMD>...]

The first word after -- is the program and the rest are its arguments; nothing is passed through a shell, so quote and glob on the host side or invoke a shell explicitly. The command is refused locally when nothing follows --. Standard output goes to the terminal's standard output and standard error to its standard error, so the two can be redirected separately.

Which account the command runs as follows the ladder in Logins. On a machine that declares a login {}, the command runs as that login rather than as the agent, so writing into a system directory starts failing where it used to work. --user SYSTEM or --user root is the old behaviour, spelled out. --user also accepts an account the lab file never declared when --password is given. A logon that cannot be minted fails naming the account and the machine.

When the command has not exited by --timeout, the daemon stops waiting and reports the timeout as a failure. A guest exit code other than zero becomes this command's exit status, so a script can test the guest command's result directly.

vmlab exec dc01 -- powershell -NoProfile -Command "Get-Service ntds | Select Status"
vmlab exec --user admin dc01 -- cmd /c whoami
vmlab exec --timeout 600 nix01 -- nix-build default.nix

Exit status is 0 when the guest command exits 0, and the guest's own exit code otherwise. not_found (4) means the lab declares no machine by that name. failed (1) covers a machine that is not running, an agent that does not answer, a login that cannot be minted, and a timeout. An empty command exits 1 before any request is sent.