On 08.01.2016 13:09, 王李明 wrote: [it's considered better practice to send just text to a mailing list instead of pictures.] Interesting. The pid 114979 you are attaching to - are you sure it's the pid of libvirtd? I tend to use: "gdb -p $(pgrep libvirtd)" and I don't have to bother with obtaining the daemon's pid. Also, ptrace seems to have failed. Reading its manpage: EPERM The specified process cannot be traced. This could be because the tracer has insufficient privileges (the required capability is CAP_SYS_PTRACE); unprivileged processes cannot trace processes that they cannot send signals to or those running set-user-ID/set-group-ID programs, for obvious reasons. Alternatively, the process may already be being traced, or (on kernels before 2.6.26) be init(1) (PID 1). Are you sure you don't lack CAP_SYS_PTRACE? # pscap | grep $$ 20740 7687 root grep full 20411 20740 root bash full Michal