Can I use GDB to debug a running process

Question

Under linux  can I use GDB to debug a process that is currently running

User · Answer

You can attach to a running process with gdb -p PID

User · Answer

Yes   You can do   gdb program name program pid   A shortcut would be  assuming only one instance is running    gdb program name  pidof program name

User · Answer

Yes   Use the attach command   Check out this link for more information   Typing help attach at a GDB console gives the following     gdb  help attach       Attach to a process or file outside of GDB    This command attaches to another target  of the same type as your last    target  command   info files  will show your target stack     The command may take as argument a process id  a process name    with an optional process-id as a suffix   or a device file    For a process id  you must have permission to send the process a signal    and it must have the same effective uid as the debugger    When using  attach  to an existing process  the debugger finds the   program running in the process  looking first in the current working   directory  or  if not found there  using the source file search path    see the  directory  command    You can also use the  file  command   to specify the program  and to load its symbol table      NOTE  You may have difficulty attaching to a process due to improved security in the Linux kernel - for example attaching to the child of one shell from another   You ll likely need to set  proc sys kernel yama ptrace scope depending on your requirements  Many systems now default to 1 or higher   The sysctl settings  writable only with CAP SYS PTRACE  are   0 - classic ptrace permissions  a process can PTRACE ATTACH to any other     process running under the same uid  as long as it is dumpable  i e      did not transition uids  start privileged  or have called     prctl PR SET DUMPABLE     already   Similarly  PTRACE TRACEME is     unchanged   1 - restricted ptrace  a process must have a predefined relationship     with the inferior it wants to call PTRACE ATTACH on  By default      this relationship is that of only its descendants when the above     classic criteria is also met  To change the relationship  an     inferior can call prctl PR SET PTRACER  debugger       to declare     an allowed debugger PID to call PTRACE ATTACH on the inferior      Using PTRACE TRACEME is unchanged   2 - admin-only attach  only processes with CAP SYS PTRACE may use ptrace     with PTRACE ATTACH  or through children calling PTRACE TRACEME   3 - no attach  no processes may use ptrace with PTRACE ATTACH nor via     PTRACE TRACEME  Once set  this sysctl value cannot be changed

User · Answer

ps -elf doesn t seem to show the PID  I recommend using instead   ps -ld   grep foo gdb -p PID

User · Answer

Yes you can  Assume a process foo is running      ps -elf   grep foo  look for the PID number  gdb -a  PID number

User · Answer

The command to use is gdb attach pid where pid is the process id of the process you want to attach to

User · Answer

If one want to attach a process  this process must have the same owner  The root is able to attach to any process

User · Answer

Easiest way is to provide the process id   gdb -p  pidof your running program name    Please get the full list of option in man gdb command   In case there are multiple process for the same program running  then the following command will list the processes   ps -C program -o pid h  lt number gt    Then the output process id  number  can be used as argument to gdb   gdb -p  lt process id gt

[linux] Can I use GDB to debug a running process?

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