[lxc-devel] [PATCH] lxc-start: add option -p, --pidfile=FILE for use with --daemon

[Serge Hallyn]

Quoting Natanael Copa (ncopa at alpinelinux.org):
> Add option to create a pidfile for lxc-start daemon. This is helpful
> for init scripts and process monitors.

Why only when daemonizing?  Someone could presumably first lxc-start
by hand in the foreground, then another admin walks in and restarts
the sysvinit lxc job?

> Signed-off-by: Natanael Copa <ncopa at alpinelinux.org>
> ---
>  doc/lxc-start.sgml.in | 12 ++++++++++++
>  src/lxc/arguments.h   |  1 +
>  src/lxc/lxc_start.c   | 24 ++++++++++++++++++++++++
>  3 files changed, 37 insertions(+)
> 
> diff --git a/doc/lxc-start.sgml.in b/doc/lxc-start.sgml.in
> index 2b6778f..bd875d6 100644
> --- a/doc/lxc-start.sgml.in
> +++ b/doc/lxc-start.sgml.in
> @@ -53,6 +53,7 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
>        <arg choice="opt">-f <replaceable>config_file</replaceable></arg>
>        <arg choice="opt">-c <replaceable>console_file</replaceable></arg>
>        <arg choice="opt">-d</arg>
> +      <arg choice="opt">-p <replaceable>pid_file</replaceable></arg>
>        <arg choice="opt">-s KEY=VAL</arg>
>        <arg choice="opt">-C</arg>
>        <arg choice="opt">command</arg>
> @@ -109,6 +110,17 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
>  
>        <varlistentry>
>  	<term>
> +	  <option>-p, --pidfile <replaceable>pid_file</replaceable></option>
> +	</term>
> +	<listitem>
> +	  <para>
> +	    Create a pidfile when running as daemon.
> +	  </para>
> +	</listitem>
> +      </varlistentry>
> +
> +      <varlistentry>
> +	<term>
>  	  <option>-f, --rcfile <replaceable>config_file</replaceable></option>
>  	</term>
>  	<listitem>
> diff --git a/src/lxc/arguments.h b/src/lxc/arguments.h
> index 40f0d6c..789ccd9 100644
> --- a/src/lxc/arguments.h
> +++ b/src/lxc/arguments.h
> @@ -45,6 +45,7 @@ struct lxc_arguments {
>  	int daemonize;
>  	const char *rcfile;
>  	const char *console;
> +	const char *pidfile;
>  
>  	/* for lxc-checkpoint/restart */
>  	const char *statefile;
> diff --git a/src/lxc/lxc_start.c b/src/lxc/lxc_start.c
> index 81a5774..a031ee1 100644
> --- a/src/lxc/lxc_start.c
> +++ b/src/lxc/lxc_start.c
> @@ -62,6 +62,7 @@ static int my_parser(struct lxc_arguments* args, int c, char* arg)
>  	case 'f': args->rcfile = arg; break;
>  	case 'C': args->close_all_fds = 1; break;
>  	case 's': return lxc_config_define_add(&defines, arg);
> +	case 'p': args->pidfile = arg; break;
>  	}
>  	return 0;
>  }
> @@ -72,6 +73,7 @@ static const struct option my_longopts[] = {
>  	{"define", required_argument, 0, 's'},
>  	{"console", required_argument, 0, 'c'},
>  	{"close-all-fds", no_argument, 0, 'C'},
> +	{"pidfile", required_argument, 0, 'p'},
>  	LXC_COMMON_OPTIONS
>  };
>  
> @@ -85,6 +87,7 @@ lxc-start start COMMAND in specified container NAME\n\
>  Options :\n\
>    -n, --name=NAME      NAME for name of the container\n\
>    -d, --daemon         daemonize the container\n\
> +  -p, --pidfile=FILE   Create pidfile when daemonized\n\
>    -f, --rcfile=FILE    Load configuration file FILE\n\
>    -c, --console=FILE   Set the file output for the container console\n\
>    -C, --close-all-fds  If any fds are inherited, close them\n\
> @@ -95,6 +98,7 @@ Options :\n\
>  	.parser    = my_parser,
>  	.checker   = NULL,
>  	.daemonize = 0,
> +	.pidfile = NULL,
>  };
>  
>  int main(int argc, char *argv[])
> @@ -200,6 +204,7 @@ int main(int argc, char *argv[])
>  	}
>  
>  	if (my_args.daemonize) {
> +		FILE *pid_fp;
>  		/* do an early check for needed privs, since otherwise the
>  		 * user won't see the error */
>  
> @@ -208,10 +213,26 @@ int main(int argc, char *argv[])
>  			return err;
>  		}
>  
> +		if (my_args.pidfile != NULL) {
> +			pid_fp = fopen(my_args.pidfile, "w");
> +			if (pid_fp == NULL) {
> +				SYSERROR("failed to create '%s'", my_args.name);
> +				return err;
> +			}
> +		}
> +
>  		if (daemon(0, 0)) {
>  			SYSERROR("failed to daemonize '%s'", my_args.name);
>  			return err;
>  		}
> +
> +		if (my_args.pidfile != NULL) {
> +			if (fprintf(pid_fp, "%d\n", getpid()) < 0) {
> +				SYSERROR("failed to write '%s'", my_args.pidfile);
> +				return err;
> +			}
> +			fclose(pid_fp);
> +		}
>  	}
>  
>  	if (my_args.close_all_fds)
> @@ -230,6 +251,9 @@ int main(int argc, char *argv[])
>  		err = -1;
>  	}
>  
> +	if (my_args.daemonize && my_args.pidfile)
> +		unlink(my_args.pidfile);
> +
>  	return err;
>  }
>  
> -- 
> 1.8.0
> 
> 
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