Troubleshooting:grsec

is the name of a patchset, that used to be freely available to harden the Linux kernel. Older versions of Alpine had a  kernel for example, which used a fork of that patchset. When you run a kernel based on that patchset on your host Linux system, you will probably run into problems with pmbootstrap because it does some things inside chroots, that is blocked by default in that patchset. One example is setting file permissions }.

There are two options:
 * run pmbootstrap with a regular kernel
 * disable the grsec specific features with sysctl while running pmbootstrap (you will probably run into other issues though, which have not been resolved - the quick solution is really using the regular kernel).

Disable some grsec-specific features while running pmbootstrap
However, user cmdr2 reported, that you can do the following to disable all grsec features, and pmbootstrap will work then:

To comprehensively disable grsec until the next reboot, I suggest:

Commands to non-native chroots hang
This can only be partially resolved as of now, see.

For starters, disable the  PaX flag: