tests: create a tmp image that has coredumps enabled for testing

[samrose]

these changes will NOT be merged into develop or promoted to production

The purpose of this draft pr is to create an image that has coredumps enabled per our internal playbook, for testing segfault issues. We will not merge this PR, or release the images created with it. It will be closed without merging when testing is completed.

[za-arthur]

I had to pass full path instead of just postmaster:

sudo gdb /nix/store/56va3gd07cakgapybcw4iq1irhx9lryx-postgresql-and-plugins-17_11/bin/.postgres-wrapped -c /pg_coredump_debug/core..postgres-wrapp.2150.1755075766

I'm not sure how properly can I find the path. One can try:

ls -lh /nix/store/*/bin/.postgres-wrapped
-r-xr-xr-x 3 root root 11M Jan  1  1970 /nix/store/56va3gd07cakgapybcw4iq1irhx9lryx-postgresql-and-plugins-17_11/bin/.postgres-wrapped

[samrose]

I think you can also find it in /var/lib/postgresql/.nix-profile/bin so there actually is already a conventional location (I just used the same "home" dir for the postgres user that infra team created before I did all the nix packaging, to make it easier for people to orient themselves who were already familiar with /var/lib/postgresql homedir)

[za-arthur]

In my case I had to use the .postgres-wrapped file which isn't in /var/lib/postgresql/.nix-profile/bin. TBH not sure how it is related to the original postgres binary file.

[samrose]

We'll end up converting this from ansible to a nix package configuration that can be installed/uninstalled this was just a short term measure/test to see if this would work