Add 'disksup_posix_only' parameter to disksup

On embedded (Linux) systems the "df" program is very often provided by
the Busybox (or Toolbox) project. This version does not provide the "-l"
option (for displaying only local filesystems) used in disksup.erl.

To make disksup work on these embedded platforms, this patch adds a new
application parameter 'disksup_posix_only', to make diskup use only
options defined in the POSIX standard:
http://pubs.opengroup.org/onlinepubs/9699919799/utilities/df.html

3 files changed, 52 insertions, 12 deletions

diff --git a/lib/os_mon/doc/src/disksup.xml b/lib/os_mon/doc/src/disksup.xml
index dbcfd65095..c8566d0126 100644
--- a/lib/os_mon/doc/src/disksup.xml
+++ b/lib/os_mon/doc/src/disksup.xml
@@ -73,6 +73,16 @@
           much disk can be utilized before the <c>disk_almost_full</c>
           alarm is set. The default is 0.80 (80%).</p>
       </item>
+      <tag><c>disksup_posix_only = bool()</c></tag>
+      <item>
+        <p>Specifies whether the <c>disksup</c> helper process should only
+          use POSIX conformant commands (<c>true</c>) or not. The default is
+          <c>false</c>. Setting this parameter to <c>true</c> can be
+          necessary on embedded systems with stripped-down versions
+          of Unix tools like <c>df</c>. The returned disk data and alarms
+          can be different when using this option.</p>
+        <p>The parameter is ignored on Windows.</p>
+      </item>
     </taglist>
     <p>See <seealso marker="kernel:config">config(4)</seealso> for
       information about how to change the value of configuration
diff --git a/lib/os_mon/src/disksup.erl b/lib/os_mon/src/disksup.erl
index 278da26a20..3fd80f2365 100644
--- a/lib/os_mon/src/disksup.erl
+++ b/lib/os_mon/src/disksup.erl
@@ -81,10 +81,12 @@ param_type(disk_space_check_interval, Val) when is_integer(Val),
 param_type(disk_almost_full_threshold, Val) when is_number(Val),
 						 0=<Val,
 						 Val=<1 -> true;
+param_type(disksup_posix_only, Val) when Val==true; Val==false -> true;
 param_type(_Param, _Val) -> false.
 
 param_default(disk_space_check_interval) -> 30;
-param_default(disk_almost_full_threshold) -> 0.80.
+param_default(disk_almost_full_threshold) -> 0.80;
+param_default(disksup_posix_only) -> false.
 
 %%----------------------------------------------------------------------
 %% gen_server callbacks
@@ -94,7 +96,8 @@ init([]) ->
     process_flag(trap_exit, true),
     process_flag(priority, low),
 
-    OS = get_os(),
+    PosixOnly = os_mon:get_env(disksup, disksup_posix_only),
+    OS = get_os(PosixOnly),
     Port = case OS of
 		{unix, Flavor} when Flavor==sunos4;
 				    Flavor==solaris;
@@ -102,6 +105,7 @@ init([]) ->
 				    Flavor==dragonfly;
 				    Flavor==darwin;
 				    Flavor==linux;
+				    Flavor==posix;
 				    Flavor==openbsd;
 				    Flavor==netbsd;
 				    Flavor==irix64;
@@ -205,8 +209,10 @@ format_status(_Opt, [_PDict, #state{os = OS, threshold = Threshold,
 %% Internal functions
 %%----------------------------------------------------------------------
 
-get_os() ->
+get_os(PosixOnly) ->
     case os:type() of
+	{unix, _} when PosixOnly ->
+	    {unix, posix};
 	{unix, sunos} ->
 	    case os:version() of
 		{5,_,_} -> {unix, solaris};
@@ -259,6 +265,9 @@ check_disk_space({unix, irix}, Port, Threshold) ->
 check_disk_space({unix, linux}, Port, Threshold) ->
     Result = my_cmd("/bin/df -lk", Port),
     check_disks_solaris(skip_to_eol(Result), Threshold);
+check_disk_space({unix, posix}, Port, Threshold) ->
+    Result = my_cmd("df -k -P", Port),
+    check_disks_solaris(skip_to_eol(Result), Threshold);
 check_disk_space({unix, dragonfly}, Port, Threshold) ->
     Result = my_cmd("/bin/df -k -t ufs,hammer", Port),
     check_disks_solaris(skip_to_eol(Result), Threshold);
diff --git a/lib/os_mon/test/disksup_SUITE.erl b/lib/os_mon/test/disksup_SUITE.erl
index 94661cfa77..2f62564959 100644
--- a/lib/os_mon/test/disksup_SUITE.erl
+++ b/lib/os_mon/test/disksup_SUITE.erl
@@ -29,6 +29,7 @@
 -export([port/1]).
 -export([terminate/1, unavailable/1, restart/1]).
 -export([otp_5910/1]).
+-export([posix_only/1]).
 
 %% Default timetrap timeout (set in init_per_testcase)
 -define(default_timeout, ?t:minutes(1)).
@@ -62,9 +63,9 @@ all() ->
     Bugs = [otp_5910],
     case test_server:os_type() of
 	{unix, sunos} ->
-	    [api, config, alarm, port, unavailable] ++ Bugs;
-	{unix, _OSname} -> [api, alarm] ++ Bugs;
-	{win32, _OSname} -> [api, alarm] ++ Bugs;
+	    [api, config, alarm, port, unavailable, posix_only] ++ Bugs;
+	{unix, _OSname} -> [api, alarm, posix_only] ++ Bugs;
+	{win32, _OSname} -> [api, alarm, posix_only] ++ Bugs;
 	_OS -> [unavailable]
     end.
 
@@ -83,12 +84,7 @@ api(doc) -> ["Test of API functions"];
 api(Config) when is_list(Config) ->
 
     %% get_disk_data()
-    [{Id,KByte,Capacity}|_] = get_disk_data(),
-    true = io_lib:printable_list(Id),
-    true = is_integer(KByte),
-    true = is_integer(Capacity),
-    true = Capacity>0,
-    true = KByte>0,
+    ok = check_get_disk_data(),
 
     %% get_check_interval()
     1800000 = disksup:get_check_interval(),
@@ -405,9 +401,34 @@ otp_5910(Config) when is_list(Config) ->
     ok = application:start(os_mon),
     ok.
 
+posix_only(suite) -> [];
+posix_only(doc) -> ["Test disksup_posix_only option"];
+posix_only(Config) when is_list(Config) ->
+    %% Set option and restart disksup
+    ok = application:set_env(os_mon, disksup_posix_only, true),
+    ok = supervisor:terminate_child(os_mon_sup, disksup),
+    {ok, _Child1} = supervisor:restart_child(os_mon_sup, disksup),
+
+    ok = check_get_disk_data(),
+
+    %% Reset option and restart disksup
+    ok = application:set_env(os_mon, disksup_posix_only, false),
+    ok = supervisor:terminate_child(os_mon_sup, disksup),
+    {ok, _Child2} = supervisor:restart_child(os_mon_sup, disksup),
+    ok.
+
 dump_info() ->
     io:format("Status: ~p~n", [sys:get_status(disksup)]).
 
+check_get_disk_data() ->
+    [{Id,KByte,Capacity}|_] = get_disk_data(),
+    true = io_lib:printable_list(Id),
+    true = is_integer(KByte),
+    true = is_integer(Capacity),
+    true = Capacity>0,
+    true = KByte>0,
+    ok.
+
 % filter get_disk_data and remove entriew with zero capacity
 % "non-normal" filesystems report zero capacity
 % - Perhaps errorneous 'df -k -l'?