Hi All, I have made it worked after seteuid in the program and export DBUS_SESSION_BUS_ADDRESS as the plain user's. I don't know why but it did work, thanks all of you a lot. <div>-- <div> Best Regards, </div> </div> 在2010-05-13 10:36:51，danny <tornadory@163.com> 写道： <blockquote id="isReplyContent" style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Hi All, I test, but unfortunately it failed. Below is my test program,  I thought the g_volume_monitor_get() need user's info, was it wrong? Normally while I run "./test" , it will monitor the removable device and show the drive's name while some devices such as USB type connected or disconnected. But when run it as root, it will show nothing. /* *   gcc -o test test.c `pkg-config --libs --cflags gtk+-2.0` *   Usage:  ./test * */ #include <gio/gio.h> #include <gtk/gtk.h> #include <string.h> #include <unistd.h> #include <errno.h> static void print_drive_info(GDrive *drive) {     gchar *name;     name = g_drive_get_name(drive);       g_print("\tname: %s\n",         name ? name : "(null)");     g_free(name); } static void on_drive_changed(GVolumeMonitor *volume_monitor, GDrive *drive) {     g_print("Drive changed:\n");     print_drive_info(drive); } static void on_drive_connected(GVolumeMonitor *volume_monitor, GDrive *drive) {     g_print("Drive connected:\n");     print_drive_info(drive); } static void on_drive_disconnected(GVolumeMonitor *volume_monitor, GDrive *drive) {     g_print("Drive disconnected:\n");     print_drive_info(drive); } static void on_refresh_clicked(GtkButton *button, Context ctx) {     refresh_drive_list(ctx); } int main(int argc, char *argv[]) {     GVolumeMonitor *monitor;     gtk_init(&argc, &argv);     /*Just for test , I set the uid euid directly to 500 which is my own user id */     int old_uid = getuid();     int old_euid = geteuid();     printf("uid is %d \n euid is %d \n",getuid(), geteuid() );     if (setuid(500) == -1)     //if (seteuid(500) == -1)     {     printf ("seteuid : %s \n", strerror(errno));     return -1;     }     printf("uid is %d \n euid is %d \n",getuid(), geteuid() );     monitor = g_volume_monitor_get();   //the main entry I get information     g_signal_connect(monitor, "drive-changed", G_CALLBACK(on_drive_changed), NULL);     g_signal_connect(monitor, "drive-connected", G_CALLBACK(on_drive_connected), NULL);     g_signal_connect(monitor, "drive-disconnected", G_CALLBACK(on_drive_disconnected), NULL);       gtk_main();     return 0; } <div>-- <div> Best Regards, </div> </div> 在2010-05-13 09:48:16，danny <<a href="mailto:tornadory@163.com">tornadory@163.com</a>> 写道： <blockquote id="isReplyContent" style="border-left: 1px solid rgb(204, 204, 204); margin: 0px 0px 0px 0.8ex; padding-left: 1ex;">Thanks all of you, I'll try it now. Thanks again. <div>-- <div> Best Regards, </div> </div> <pre> 在2010-05-13 00:26:45，"Thiago Macieira" <<a href="mailto:thiago@kde.org">thiago@kde.org</a>> 写道： >Em Quarta-feira 12 Maio 2010, às 18:02:10, Rémi Denis-Courmont escreveu: >> Le mercredi 12 mai 2010 14:04:40 Thiago Macieira, vous avez écrit : >> > Em Quarta-feira 12. Maio 2010, às 12.13.06, danny escreveu: >> > > Dear All, >> > >  >> > > I have a program run as root, but I need get information from GVFS >> > > which is on the session bus, and it shows "failed to connect the >> > > session bus" while I run the test program, and it could not get any >> > > information from the GVFS. >> > >  >> > > Could I access the session bus in my "root" program? >> >  >> > No. >> >  >> > The user's session bus requires the user's UID. Your program needs to >> > drop privileges before connecting. >>  >> I think, in principles, the root process could just set its effective UID >> to the user, while establishing the DBus connection, then back to root. It >> does not need to drop the root privileges. > >Well, setting the EUID is dropping the privileges, even if you can still take  >them back later :-) > >--  >Thiago Macieira - thiago (AT) macieira.info - thiago (AT) kde.org >  Senior Product Manager - Nokia, Qt Development Frameworks >      PGP/GPG: 0x6EF45358; fingerprint: >      E067 918B B660 DBD1 105C  966C 33F5 F005 6EF4 5358 </pre> <hr> <a href="http://ym.163.com/?from=od3" target="_blank">网易为中小企业免费提供企业邮箱（自主域名）</a> </blockquote> </blockquote>