Use bash as the default shell for ssh connect interactive sessions

NEXT_CHANGELOG.md

@@ -5,6 +5,7 @@
 ### Notable Changes
 
 ### CLI
+* `databricks ssh connect` now opens an interactive `bash` login shell by default instead of the compute image's default `/bin/sh`, falling back gracefully when `bash` is unavailable. Passing an explicit remote command (`-- <cmd>`) is unaffected ([#5687](https://github.com/databricks/cli/pull/5687)).
 
 ### Bundles
 * `bundle run` now prints the modern job run URL (`/jobs/<id>/runs/<id>`) so that non-admin users permitted to view the run are taken to the run instead of the workspace homepage.

experimental/ssh/internal/client/client.go

@@ -612,6 +612,22 @@ func submitSSHTunnelJob(ctx context.Context, client *databricks.WorkspaceClient,
 	return waiter.RunId, waitForJobToStart(ctx, client, waiter.RunId, opts.TaskStartupTimeout)
 }
 
+// buildRemoteShellArgs returns the ssh arguments that follow the hostname.
+//
+// For the interactive case (no remote command given), it forces PTY allocation
+// and launches a login bash, because the default login shell on Databricks
+// compute images is /bin/sh. If bash is unavailable it falls back to $SHELL or
+// /bin/sh so the connection never breaks.
+//
+// For the non-interactive case (e.g. `databricks ssh connect ... -- ls -la`),
+// the user's command is returned verbatim so behavior is unchanged.
+func buildRemoteShellArgs(opts ClientOptions) []string {
+	if len(opts.AdditionalArgs) > 0 {
+		return opts.AdditionalArgs
+	}
+	return []string{"-t", `command -v bash >/dev/null 2>&1 && exec bash -l || exec "${SHELL:-/bin/sh}" -l`}
+}
+
 func spawnSSHClient(ctx context.Context, client *databricks.WorkspaceClient, userName, privateKeyPath string, serverPort int, clusterID string, opts ClientOptions) error {
 	// Create a copy with metadata for the ProxyCommand
 	optsWithMetadata := opts
@@ -636,7 +652,7 @@ func spawnSSHClient(ctx context.Context, client *databricks.WorkspaceClient, use
 		sshArgs = append(sshArgs, "-o", "UserKnownHostsFile="+opts.UserKnownHostsFile)
 	}
 	sshArgs = append(sshArgs, hostName)
-	sshArgs = append(sshArgs, opts.AdditionalArgs...)
+	sshArgs = append(sshArgs, buildRemoteShellArgs(opts)...)
 
 	log.Debugf(ctx, "Launching SSH client: ssh %s", strings.Join(sshArgs, " "))
 	sshCmd := exec.CommandContext(ctx, "ssh", sshArgs...)

experimental/ssh/internal/client/client_internal_test.go

@@ -198,6 +198,22 @@ func TestHostKeyChangedHint(t *testing.T) {
 	}
 }
 
+func TestBuildRemoteShellArgs(t *testing.T) {
+	t.Run("interactive launches login bash with PTY", func(t *testing.T) {
+		args := buildRemoteShellArgs(ClientOptions{})
+		require.Len(t, args, 2)
+		assert.Equal(t, "-t", args[0])
+		assert.Equal(t, `command -v bash >/dev/null 2>&1 && exec bash -l || exec "${SHELL:-/bin/sh}" -l`, args[1])
+	})
+
+	t.Run("non-interactive passes additional args verbatim", func(t *testing.T) {
+		additional := []string{"ls", "-la"}
+		args := buildRemoteShellArgs(ClientOptions{AdditionalArgs: additional})
+		assert.Equal(t, additional, args)
+		assert.NotContains(t, args, "-t")
+	})
+}
+
 func TestTailWriterRetainsTail(t *testing.T) {
 	t.Run("retains only the tail", func(t *testing.T) {
 		w := &tailWriter{maxBytes: 4}