[systemd-devel] Tips for using GDB to analyze systemd init process (`/sbin/init`)

[Lennart Poettering]

On Sat, 14.03.15 09:14, Paul Menzel (paulepanter at users.sourceforge.net) wrote:

> Dear systemd folks,
> 
> 
> using Debian Sid/unstable with systemd 215-12, I attached to it with GDB
> to analyze some things. Attached with `gdb --pid 1` worked.
> 
> But continuing the execution and then hitting Ctrl + c to stop and
> analyze it again, systemd caught that command and shut the system down.
> 
> How do you accomplish the goal to analyze systemd with GDB?

All programs that use signalfd() are really nasty to debug in gdb,
since gdb doesn't catch the Ctl-C then anymore via ptrace, but it gets
delivered to the signalfd instead, and thus handled by the app anyway.

To work around this: keep a second terminal open and send SIGTRAP from
there. 

I usually carefully set break points though so that I never have to
deal with PID 1 running uncontrolled in gdb though...

Lennart

-- 
Lennart Poettering, Red Hat