Re: [Libguestfs] simplify debugging of guestfsd
On Fri, Sep 21, Richard W.M. Jones wrote:
The problem with collecting core dumps is how you get them out of
the
appliance, given that it is short-lived and disappears on exit. We
looked at various methods including writing them to a block device or
squirting it down a virtio-serial connection, but none of them are
very satisfactory.
Yes, getting a file out of the guest is tricky.
strace output can do through the usual console logging mechanism.
Yes, my take would be 'var="strace -f -s 123 -tt" ; $var guestfsd'.
gdb seems intractable to me if you want to use gdb interactively.
Just printing stack traces can go via the console logging mechanism.
Note there's very limited development tools in the appliance (no
debuginfo), and I'd be cautious about how much stuff gdb will pull in
via dependencies. That's why we looked at core dumps.
gdb is certainly more advanced, something like 'var="gdb --readnow -ex r
-ex bt -ex quit' ; $var guestfsd' would be good enough, or gdb
--command=FILE.
As you say, without adding debuginfo into guest the backtrace would be
not that useful. But its better than nothing.
Yesterday I tried to run guestfsd via gdb, and it required a few python
files. But it turned out that the actual segfault happend in the host,
not the guest. So I did not look further if gdb did really work.
Olaf