Debugging Options

The debugging options come in two groupsthose that make kernel debugging possible in tt mode and those that disable use of host features in order to narrow down UML problems.

In the first group are two options for specifying that we want debugging and whether we want to use an already-running debugger.

• debug In tt mode, this causes UML to bring up gdb in an xterm window in order to debug the UML kernel.

• gdb-pid=<pid> In tt mode, this switch specifies the process ID of an already-running debugger that the instance should attach to.

These may go away in the future if tt mode support is removed from UML.

The second group of options allows you to selectively disable the use of various host capabilities.

• aio=2.4 This switch causes UML to avoid the use of the AIO support on the host if it's present and to fall back to its own I/O thread, which can keep one request in flight at a time.

• mode=tt This specifies that the UML instance should use tt mode rather than skas mode.

• mode=skas0 and skas0 Both of these switches avoid the use of the skas3 patch if it's present on the host, causing UML to use skas0 mode, unless mode=tt is also specified, in which case tt mode will be used.

• nosysemu This avoids the use of the sysemu patch if it's present on the host.

• noprocmm This avoids the use of /proc/mm if the skas3 patch is present on the host.

• noptracefaultinfo This avoids the use of PTRACE_FAULTINFO if the skas3 patch is present on the host.