[shim] Change NVIDIA GPU detection method

* Check for `/dev/nvidiactl`, not `nvidia-smi` binary, to detect NVIDIA
  GPU. Unlike the binary, the devfs file only exists if some conditions
  are met (the exact way how `/dev/ndivia*` character device files are
  created is complicated and setup-specific — involving some of: kernel
  module, udev, modprobe, nvidia-persistenced, X server, and more — but
  in general, it should be safe to assume that if NVIDIA GPU
  is available, then `/dev/nvidiactl` does exist.
* Run `nvidia-smi` to get GPU info directly on the host, not inside a
  container. Using Docker is completely unnecessary, as NVIDIA Container
  Toolkit mounts libs and executables from the host — dstack-provided
  Docker image doesn't even contain `nvidia-smi` binary, it's always
  a bind-mounted file from the host.

Fixes: #1942

runner/README.md

@@ -97,6 +97,7 @@ These are nonexhaustive lists of external dependencies (executables, libraries)
 * `mountpoint`
 * `lsblk`
 * `mkfs.ext4`
+* (NVIDIA GPU SSH fleet instances only) `nvidia-smi`
 * ...
 
 Debian/Ubuntu packages: `mount` (`mount`, `umount`), `util-linux` (`mountpoint`, `lsblk`), `e2fsprogs` (`mkfs.ext4`)

runner/internal/shim/gpu.go

@@ -8,14 +8,12 @@ import (
 	"io"
 	"log"
 	"os"
-	"os/exec"
 	"strconv"
 	"strings"
 
 	execute "github.com/alexellis/go-execute/v2"
 )
 
-const nvidiaSmiImage = "dstackai/base:py3.13-0.6-cuda-12.1"
 const amdSmiImage = "un1def/amd-smi:6.2.2-0"
 
 type GpuVendor string
@@ -36,7 +34,7 @@ func GetGpuVendor() GpuVendor {
 	if _, err := os.Stat("/dev/kfd"); !errors.Is(err, os.ErrNotExist) {
 		return Amd
 	}
-	if _, err := exec.LookPath("nvidia-smi"); err == nil {
+	if _, err := os.Stat("/dev/nvidiactl"); !errors.Is(err, os.ErrNotExist) {
 		return Nvidia
 	}
 	return NoVendor
@@ -56,14 +54,8 @@ func getNvidiaGpuInfo() []GpuInfo {
 	gpus := []GpuInfo{}
 
 	cmd := execute.ExecTask{
-		Command: "docker",
-		Args: []string{
-			"run",
-			"--rm",
-			"--gpus", "all",
-			nvidiaSmiImage,
-			"nvidia-smi", "--query-gpu=gpu_name,memory.total", "--format=csv,nounits",
-		},
+		Command:     "nvidia-smi",
+		Args:        []string{"--query-gpu=gpu_name,memory.total", "--format=csv,nounits"},
 		StreamStdio: false,
 	}
 	res, err := cmd.Execute(context.Background())