# General Information * [[/hurd/subhurd]] --- # Debugging the Hurd Startup Process _one.full_ is the subhurd's root file system image and has been installed as follows: [TODO] _Wx_ translates to terminal window _x_. W1 $ fsysopts one.full/ --readonly $ sudo boot -I -d -s -D one.full/ one.full/boot/script.boot one.full.ext2 Pausing. . . (In theory it shouldn't be neccessary to run the subhurd as user _root_, but in practice [that doesn't work at the moment](http://savannah.gnu.org/bugs/?17341).) W2 $ ps -Af [...] root 851 385 p4 0:00.01 boot -I -d -s -D one.full/ one.full/boot/script.boot one.full.ext2 - 853 1 ? 0:00.00 ? - 854 1 ? 0:00.00 ? [...] $ sudo gdb /var/tmp/one.full/hurd/ext2fs.static [...] (gdb) attach 853 Attaching to program `/var/tmp/one.full/hurd/ext2fs.static', pid 853 warning: Can't modify tracing state for pid 853: No signal thread Can't fetch registers from thread 1: No such thread (The _boot_ program [could be modified to print out the pids](http://savannah.gnu.org/bugs/?19254), so that one wouldn't have to fumble with _ps_.) W3 $ sudo gdb /var/tmp/one.full/lib/ld.so.1 [...] (gdb) set solib-absolute-prefix /var/tmp/one.full (gdb) attach 854 Attaching to program `/var/tmp/one.full/lib/ld.so.1', pid 854 warning: Can't modify tracing state for pid 854: No signal thread Can't fetch registers from thread 1: No such thread W1 [<Enter>.] /hurd/ext2fs.static --bootflags=-dsf --host-priv-port=38 --device-master-port=43 --exec-server-task=47 -Tdevice pseudo-root /lib/ld.so.1 /hurd/exec Now that this step has been accomplished, you can set break points in GDB, etc. W2 (gdb) continue Continuing. warning: Can't wait for pid 853: No child processes W1 Hurd server bootstrap: ext2fs.static[pseudo-root] exec W3 (gdb) continue Continuing. warning: Can't wait for pid 854: No child processes Program received signal EXC_BAD_ACCESS, Could not access memory. __mach_port_mod_refs (task=1, name=139802, right=1, delta=-1) at /var/tmp/glibc-2_5-branch/build_--without-tls_--without-__thread/mach/RPC_mach_port_mod_refs.c:132 132 InP->Head.msgh_reply_port = __mig_get_reply_port(); (gdb) x/i $pc 0x168f2 <__mach_port_mod_refs+82>: call 0x151b0 <__mig_get_reply_port> --- Sources: * <http://www.gnu.org/software/hurd/howto/subhurd.html> * <http://lists.gnu.org/archive/html/bug-hurd/2007-02/msg00030.html> * [[Thomas_Schwinge|tschwinge]]'s mind