[PATCH] core: add startup option to provide different configuration file

[PATCH] core: add startup option to provide different configuration file

[Simon Fels]

In some cases it's needed to select a different configuration file
at runtime than the one we load by default from a statically
configured path. This adds an optional argument to the daemon
startup which will enable us to load another a configuration file
from a different path.
---
 src/main.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/src/main.c b/src/main.c
index 4c94a69..494b809 100644
--- a/src/main.c
+++ b/src/main.c
@@ -453,6 +453,7 @@ static guint setup_signalfd(void)
 static char *option_debug = NULL;
 static char *option_plugin = NULL;
 static char *option_noplugin = NULL;
+static char *option_conf = NULL;
 static gboolean option_compat = FALSE;
 static gboolean option_detach = TRUE;
 static gboolean option_version = FALSE;
@@ -547,6 +548,9 @@ static GOptionEntry options[] = {
 	{ "nodetach", 'n', G_OPTION_FLAG_REVERSE,
 				G_OPTION_ARG_NONE, &option_detach,
 				"Run with logging in foreground" },
+	{ "conf", 'c', 0, G_OPTION_ARG_STRING, &option_conf,
+				"Specify main configuration file to load. Will use "
+				CONFIGDIR "/main.conf by default", "CONF" },
 	{ "version", 'v', 0, G_OPTION_ARG_NONE, &option_version,
 				"Show version information and exit" },
 	{ NULL },
@@ -561,6 +565,7 @@ int main(int argc, char *argv[])
 	int gdbus_flags = 0;
 	guint signal, watchdog;
 	const char *watchdog_usec;
+	char *config_path = CONFIGDIR "/main.conf";
 
 	init_defaults();
 
@@ -593,7 +598,11 @@ int main(int argc, char *argv[])
 
 	sd_notify(0, "STATUS=Starting up");
 
-	main_conf = load_config(CONFIGDIR "/main.conf");
+	if (option_conf && g_file_test(option_conf, G_FILE_TEST_EXISTS |
+				G_FILE_TEST_IS_REGULAR) == TRUE)
+		config_path = option_conf;
+
+	main_conf = load_config(config_path);
 
 	parse_config(main_conf);
 
-- 
2.1.4

Re: [PATCH] core: add startup option to provide different configuration file

[Simon Fels]

On 16.09.2015 07:52, Simon Fels wrote:
> In some cases it's needed to select a different configuration file
> at runtime than the one we load by default from a statically
> configured path. This adds an optional argument to the daemon
> startup which will enable us to load another a configuration file
> from a different path.
> ---
>   src/main.c | 11 ++++++++++-
>   1 file changed, 10 insertions(+), 1 deletion(-)


For a better understanding, our use case for this is the following:

On Ubuntu we create set of packages out of the BlueZ source which are 
used across all devices we support. We don't want to put any device 
specifics in these and use the same binaries (per architecture) on 
different device types (laptops, phones, ...). By default we ship the 
main.conf file coming with the BlueZ sources. For different device types 
we now need different settings as we need to specify different settings 
for class of device field for example. At the moment there is an 
additional package only used for phones which ships a modified 
configuration file which can't replace the one provided by the bluez 
package and is then passed to bluetoothd in an .override upstart job.

regards,
Simon

Re: [PATCH] core: add startup option to provide different configuration file

[Marcel Holtmann]

Hi Simon,

>> In some cases it's needed to select a different configuration file
>> at runtime than the one we load by default from a statically
>> configured path. This adds an optional argument to the daemon
>> startup which will enable us to load another a configuration file
>> from a different path.
>> ---
>>  src/main.c | 11 ++++++++++-
>>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> 
> For a better understanding, our use case for this is the following:
> 
> On Ubuntu we create set of packages out of the BlueZ source which are used across all devices we support. We don't want to put any device specifics in these and use the same binaries (per architecture) on different device types (laptops, phones, ...). By default we ship the main.conf file coming with the BlueZ sources. For different device types we now need different settings as we need to specify different settings for class of device field for example. At the moment there is an additional package only used for phones which ships a modified configuration file which can't replace the one provided by the bluez package and is then passed to bluetoothd in an .override upstart job.

actually BlueZ is designed to run without the main.conf present and has proper defaults. That is also the reason why we are not installing any of these files in the first place.

That background here is simple that a distro can have a package that installs the correct platform specific configuration if it wants one. We have been doing this dating back to the MeeGo days. Meaning you normally have a meta package bluez-config (or something like that) and then you platform specific package with all the configurations provides this meta package. That way it is in full hands of the distro install the right packages.

So I think your solution should actually be to take main.conf out of the BlueZ package. And shove different main.conf in different platform packages.

And btw. this is how we have treated oFono, ConnMan, BlueZ and all the other projects. The times where configuration files were required are over. The daemon will start with appropriate defaults.

This becomes even more important with systemd where BlueZ will actually ship the unit file. There should be no need to do anything different and hack some different daemon option into the unit file. The bluetoothd is by its definition a singleton since it is the owner of the D-Bus bus name. That is highly woven into how systemd handles D-Bus autostart. That means that multiple units or instances for BlueZ are not a good idea. So there should be only a single main.conf location and it should be optional.

If your packages are not set up for doing this cleanly, then you could do this via bind mount of main.conf to map another file into that location. You could bind mount the whole /etc/bluetooth if you insist to. However I would strongly advise to look into the packaging strategy of the distro first. It sounds like that can be improved.

The one thing that we have not implemented yet is that we support package configuration in /usr/lib/bluetooth/config (owned by the package). These files can then be overwritten by /etc/bluetooth and maybe /run/bluetooth similar to what systemd and all its daemon currently support. The reason why we have not done that yet is mainly that we have sane defaults for values hardcoded in the daemon. However it would give packagers an option to ship other default than the hardcoded ones.

This will however not solve your problem either btw. The modern way of understanding /etc is that this is for sysadmin/users (meaning humans) to do configuration. And if you wipe it the system comes back in its factory defaults. So even if we had /usr/lib/bluetooth/config you should still apply the meta package concept from above.

Regards

Marcel