Ujail command line questions

twinkleLED · April 28, 2025, 5:42pm

Three questions....

ujail seems to add a starting and finishing "jail: " line to stdout. Is there a way to prevent ujail from generating this?

root@fuz:~# ujail -n jailName -F -c -E -U nobody -G nogroup  -- /bin/echo goooooooo
jail: exec-ing /bin/echo
goooooooo
jail: jail (29354) exited with exit: 0
root@fuz:~#

How do I generate a "capabilities drop config" compatible with ujail -C?

Where can I find the source code for ujail command line to look up other undocumented options like -t?

dave14305 · April 28, 2025, 6:05pm

github.com/openwrt/procd

jail/jail.c

891094aef


      
          		free_and_exit(EXIT_FAILURE);
          
          	if (opts.cwd && chdir(opts.cwd))
          		free_and_exit(EXIT_FAILURE);
          
          	if (opts.ociseccomp && applyOCIlinuxseccomp(opts.ociseccomp))
          		free_and_exit(EXIT_FAILURE);
          
          	uloop_end();
          	free_opts(false);
          	INFO("exec-ing %s\n", *opts.jail_argv);
          	if (opts.envp) /* respect PATH if potentially set in ENV */
          		execvpe(*opts.jail_argv, opts.jail_argv, envp);
          	else
          		execve(*opts.jail_argv, opts.jail_argv, envp);
          
          	/* we get there only if execve fails */
          	ERROR("failed to execve %s: %m\n", *opts.jail_argv);
          	exit(EXIT_FAILURE);
          }

github.com/openwrt/procd

jail/jail.c

891094aef


      
          
          	/* default 5 seconds timeout after SIGTERM before SIGKILL is sent */
          	opts.term_timeout = 5;
          
          	umask(022);
          	mount_list_init();
          	init_library_search();
          	cgroups_prepare();
          	exit_from_child = false;
          
          	while ((ch = getopt(argc, argv, OPT_ARGS)) != -1) {
          		switch (ch) {
          		case 'd':
          			debug = atoi(optarg);
          			break;
          		case 'e':
          			enve = calloc(1, sizeof(*enve));
          			enve->envarg = optarg;
          			list_add_tail(&enve->list, &envl);
          			break;
          		case 'p':