hostnamed: check that nss-myhostname is installed

TODO

@@ -22,6 +22,8 @@ Features:
 * Make it possible to set the keymap independently from the font on
   the kernel cmdline. Right now setting one resets also the other.
 
+* add dbus call to convert snapshot ino target
+
 * make use of TIOCVHANGUP
 
 * move /selinux to /sys/fs/selinux

src/hostnamed.c

@@ -24,6 +24,7 @@
 #include <errno.h>
 #include <string.h>
 #include <unistd.h>
+#include <dlfcn.h>
 
 #include "util.h"
 #include "strv.h"
@@ -110,6 +111,18 @@ static int read_data(void) {
         return 0;
 }
 
+static bool check_nss(void) {
+
+        void *dl;
+
+        if ((dl = dlopen("libnss_myhostname.so.2", RTLD_LAZY))) {
+                dlclose(dl);
+                return true;
+        }
+
+        return false;
+}
+
 static const char* fallback_icon_name(void) {
 
 #if defined(__i386__) || defined(__x86_64__)
@@ -663,6 +676,9 @@ int main(int argc, char *argv[]) {
                 goto finish;
         }
 
+        if (!check_nss())
+                log_warning("Warning: nss-myhostname is not installed. Changing the local hostname might make it unresolveable. Please install nss-myhostname!");
+
         umask(0022);
 
         r = read_data();