dlck: warn when running not as root or a daos_server group member

src/utils/dlck/dlck_main.c

@@ -7,17 +7,59 @@
 
 #include <stdlib.h>
 #include <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
 #include <abt.h>
 
 #include <daos_errno.h>
 #include <daos/debug.h>
+#include <daos/rpc.h>
 #include <daos_srv/daos_engine.h>
 #include <gurt/common.h>
 
 #include "dlck_args.h"
 #include "dlck_checker.h"
 #include "dlck_cmds.h"
 
+#define EFFECTIVE_USER_STR "Effective user: "
+#define UNEXPECTED_USER_WARNING_MSG                                                                \
+	"WARNING: It is recommended to run this program as root or user '" DAOS_DEFAULT_SYS_NAME   \
+	"'.\n"                                                                                     \
+	"These accounts are expected to have the necessary privileges.\n"                          \
+	"Running under other users may cause the program to stop due to insufficient "             \
+	"privileges.\n\n"
+
+static void
+check_user(struct checker *ck)
+{
+	uid_t          euid = geteuid();
+	struct passwd *pw;
+	int            ret;
+
+	/** The root user is not always named "root" but its uid is always 0. */
+	if (euid == 0) {
+		/** the root user have all the privileges */
+		CK_PRINT(ck, EFFECTIVE_USER_STR "root\n");
+		return;
+	}
+
+	pw = getpwuid(euid);
+	if (pw == NULL || pw->pw_name == NULL) {
+		ret = d_errno2der(errno);
+		CK_PRINTFL_RC(ck, ret, "Cannot get the name of a user for uid=%" PRIuMAX,
+			      (uintmax_t)euid);
+	}
+
+	if (strncmp(pw->pw_name, DAOS_DEFAULT_SYS_NAME, DAOS_SYS_NAME_MAX) == 0) {
+		/** the daos_server user ought to have all the necessary privileges */
+		CK_PRINT(ck, EFFECTIVE_USER_STR DAOS_DEFAULT_SYS_NAME "\n");
+		return;
+	}
+
+	CK_PRINTF(ck, EFFECTIVE_USER_STR "%s (uid=%" PRIuMAX ")\n", pw->pw_name, (uintmax_t)euid);
+	CK_PRINT(ck, UNEXPECTED_USER_WARNING_MSG);
+}
+
 int
 main(int argc, char *argv[])
 {
@@ -48,6 +90,8 @@ main(int argc, char *argv[])
 		goto err_abt_fini;
 	}
 
+	check_user(&ctrl.checker);
+
 	rc = dlck_cmd_check(&ctrl);
 	if (rc != DER_SUCCESS) {
 		goto err_print_main_fini;