Blackscreen on bootup after switching to 25.11 or unstable

Help
1

Dear Community,

I recently encountered the problem of my login screen showing a black screen with a static underscore in the upper left corner after upgrading nixos and nixpkgs to 25.11 or unstable.

The only change I made from my last working config was to change the nixpkgs version and adapt from:

  # Enable the X11 windowing system.
  services.xserver.enable = true;

  # Enable the GNOME Desktop Environment.
  services.xserver.displayManager.gdm.enable = true;
  services.xserver.desktopManager.gnome.enable = true;
  services.displayManager.enable = true;

to:

  services.displayManager.gdm.enable = true;
  services.desktopManager.gnome.enable = true;

like it was described in the wiki

After switching back to my functioning build I inspected the log:

>journalctl -b -1 -p err..alert
Dez 10 02:58:46 laptop .gnome-session-[1313]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.
Dez 10 02:58:46 laptop systemd-coredump[1322]: Process 1313 (.gnome-session-) of user 60578 dumped core.
                                               
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Stack trace of thread 1313:
                                               #0  0x00007f18b450e12f g_log_structured_array (libglib-2.0.so.0 + 0x6f12f)
                                               #1  0x00007f18b450e617 g_log_default_handler (libglib-2.0.so.0 + 0x6f617)
                                               #2  0x00007f18b450e8bc g_logv (libglib-2.0.so.0 + 0x6f8bc)
                                               #3  0x00007f18b450ec2f g_log (libglib-2.0.so.0 + 0x6fc2f)
                                               #4  0x0000564fa3acf7de main (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x27de)
                                               #5  0x00007f18b422a4d8 __libc_start_call_main (libc.so.6 + 0x2a4d8)
                                               #6  0x00007f18b422a59b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a59b)
                                               #7  0x0000564fa3acfa95 _start (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x2a95)
                                               
                                               Stack trace of thread 1320:
                                               #0  0x00007f18b4314a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f18b4504f68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f18b4505967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #3  0x00007f18b474180e gdbus_shared_thread_func (libgio-2.0.so.0 + 0x14180e)
                                               #4  0x00007f18b453889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f18b429a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f18b4322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1319:
                                               #0  0x00007f18b4314a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f18b4504f68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f18b450570f g_main_context_iteration (libglib-2.0.so.0 + 0x6670f)
                                               #3  0x00007f18b4505761 glib_worker_main (libglib-2.0.so.0 + 0x66761)
                                               #4  0x00007f18b453889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f18b429a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f18b4322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1318:
                                               #0  0x00007f18b43208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007f18b4538129 g_cond_wait (libglib-2.0.so.0 + 0x99129)
                                               #2  0x00007f18b44c8cab g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29cab)
                                               #3  0x00007f18b4538b8f g_thread_pool_spawn_thread (libglib-2.0.so.0 + 0x99b8f)
                                               #4  0x00007f18b453889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f18b429a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f18b4322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               ELF object binary architecture: AMD x86-64
Dez 10 02:58:47 laptop .gnome-session-[1364]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.
Dez 10 02:58:47 laptop systemd-coredump[1373]: Process 1364 (.gnome-session-) of user 60580 dumped core.
                                               
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Stack trace of thread 1364:
                                               #0  0x00007fb6408a912f g_log_structured_array (libglib-2.0.so.0 + 0x6f12f)
                                               #1  0x00007fb6408a9617 g_log_default_handler (libglib-2.0.so.0 + 0x6f617)
                                               #2  0x00007fb6408a98bc g_logv (libglib-2.0.so.0 + 0x6f8bc)
                                               #3  0x00007fb6408a9c2f g_log (libglib-2.0.so.0 + 0x6fc2f)
                                               #4  0x0000559c3c1fe7de main (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x27de)
                                               #5  0x00007fb64062a4d8 __libc_start_call_main (libc.so.6 + 0x2a4d8)
                                               #6  0x00007fb64062a59b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a59b)
                                               #7  0x0000559c3c1fea95 _start (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x2a95)
                                               
                                               Stack trace of thread 1369:
                                               #0  0x00007fb6407208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007fb6408d3129 g_cond_wait (libglib-2.0.so.0 + 0x99129)
                                               #2  0x00007fb640863cab g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29cab)
                                               #3  0x00007fb6408d3b8f g_thread_pool_spawn_thread (libglib-2.0.so.0 + 0x99b8f)
                                               #4  0x00007fb6408d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fb64069a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fb640722d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1371:
                                               #0  0x00007fb640714a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007fb64089ff68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007fb6408a0967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #3  0x00007fb640b4180e gdbus_shared_thread_func (libgio-2.0.so.0 + 0x14180e)
                                               #4  0x00007fb6408d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fb64069a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fb640722d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1370:
                                               #0  0x00007fb640714a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007fb64089ff68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007fb6408a070f g_main_context_iteration (libglib-2.0.so.0 + 0x6670f)
                                               #3  0x00007fb6408a0761 glib_worker_main (libglib-2.0.so.0 + 0x66761)
                                               #4  0x00007fb6408d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fb64069a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fb640722d2c __clone3 (libc.so.6 + 0x122d2c)
                                               ELF object binary architecture: AMD x86-64
Dez 10 02:58:47 laptop .gnome-session-[1393]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.
Dez 10 02:58:47 laptop systemd-coredump[1402]: Process 1393 (.gnome-session-) of user 60578 dumped core.
                                               
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Stack trace of thread 1393:
                                               #0  0x00007fe3dd4a912f g_log_structured_array (libglib-2.0.so.0 + 0x6f12f)
                                               #1  0x00007fe3dd4a9617 g_log_default_handler (libglib-2.0.so.0 + 0x6f617)
                                               #2  0x00007fe3dd4a98bc g_logv (libglib-2.0.so.0 + 0x6f8bc)
                                               #3  0x00007fe3dd4a9c2f g_log (libglib-2.0.so.0 + 0x6fc2f)
                                               #4  0x00005576c17397de main (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x27de)
                                               #5  0x00007fe3dd22a4d8 __libc_start_call_main (libc.so.6 + 0x2a4d8)
                                               #6  0x00007fe3dd22a59b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a59b)
                                               #7  0x00005576c1739a95 _start (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x2a95)
                                               
                                               Stack trace of thread 1398:
                                               #0  0x00007fe3dd3208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007fe3dd4d3129 g_cond_wait (libglib-2.0.so.0 + 0x99129)
                                               #2  0x00007fe3dd463cab g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29cab)
                                               #3  0x00007fe3dd4d3b8f g_thread_pool_spawn_thread (libglib-2.0.so.0 + 0x99b8f)
                                               #4  0x00007fe3dd4d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fe3dd29a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fe3dd322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1400:
                                               #0  0x00007fe3dd314a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007fe3dd49ff68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007fe3dd4a0967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #3  0x00007fe3dd74180e gdbus_shared_thread_func (libgio-2.0.so.0 + 0x14180e)
                                               #4  0x00007fe3dd4d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fe3dd29a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fe3dd322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1399:
                                               #0  0x00007fe3dd314a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007fe3dd49ff68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007fe3dd4a070f g_main_context_iteration (libglib-2.0.so.0 + 0x6670f)
                                               #3  0x00007fe3dd4a0761 glib_worker_main (libglib-2.0.so.0 + 0x66761)
                                               #4  0x00007fe3dd4d389d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007fe3dd29a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007fe3dd322d2c __clone3 (libc.so.6 + 0x122d2c)
                                               ELF object binary architecture: AMD x86-64
Dez 10 02:58:47 laptop .gnome-session-[1436]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.
Dez 10 02:58:47 laptop systemd-coredump[1445]: Process 1436 (.gnome-session-) of user 60580 dumped core.
                                               
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Stack trace of thread 1436:
                                               #0  0x00007f361d70e12f g_log_structured_array (libglib-2.0.so.0 + 0x6f12f)
                                               #1  0x00007f361d70e617 g_log_default_handler (libglib-2.0.so.0 + 0x6f617)
                                               #2  0x00007f361d70e8bc g_logv (libglib-2.0.so.0 + 0x6f8bc)
                                               #3  0x00007f361d70ec2f g_log (libglib-2.0.so.0 + 0x6fc2f)
                                               #4  0x000056303c9887de main (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x27de)
                                               #5  0x00007f361d42a4d8 __libc_start_call_main (libc.so.6 + 0x2a4d8)
                                               #6  0x00007f361d42a59b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a59b)
                                               #7  0x000056303c988a95 _start (/nix/store/h8ly69z9wi7rxhdyi432w93zqba10r25-gnome-session-49.2/libexec/.gnome-session-init-worker-wrapped + 0x2a95)
                                               
                                               Stack trace of thread 1441:
                                               #0  0x00007f361d5208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007f361d738129 g_cond_wait (libglib-2.0.so.0 + 0x99129)
                                               #2  0x00007f361d6c8cab g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29cab)
                                               #3  0x00007f361d738b8f g_thread_pool_spawn_thread (libglib-2.0.so.0 + 0x99b8f)
                                               #4  0x00007f361d73889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f361d49a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f361d522d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1442:
                                               #0  0x00007f361d514a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f361d704f68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f361d70570f g_main_context_iteration (libglib-2.0.so.0 + 0x6670f)
                                               #3  0x00007f361d705761 glib_worker_main (libglib-2.0.so.0 + 0x66761)
                                               #4  0x00007f361d73889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f361d49a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f361d522d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1443:
                                               #0  0x00007f361d514a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f361d704f68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f361d705967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #3  0x00007f361d94180e gdbus_shared_thread_func (libgio-2.0.so.0 + 0x14180e)
                                               #4  0x00007f361d73889d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f361d49a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f361d522d2c __clone3 (libc.so.6 + 0x122d2c)
                                               ELF object binary architecture: AMD x86-64
Dez 10 02:58:47 laptop .gnome-session-[1465]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.
Dez 10 02:58:47 laptop systemd-coredump[1474]: Process 1465 (.gnome-session-) of user 60578 dumped core.
                                               
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Stack trace of thread 1465:
                                               #0  0x00007f4fe3ca912f g_log_structured_array (libglib-

-------- also snipped here to not get over the character count -------

Dez 10 02:58:47 laptop .gnome-session-[1494]: Failed to start unit gnome-session-x11@gnome-login.target: GDBus.Error:org.freedesktop.systemd1.NoSuchUnit: Unit gnome-session-x11@gnome-login.target not found.

-------- snipped here ----------

Dez 10 02:58:51 laptop systemd-coredump[2008]: Process 1738 (gdm) of user 0 dumped core.
                                               
                                               Module libcrypt.so.2 without build-id.
                                               Module libselinux.so.1 without build-id.
                                               Module libz.so.1 without build-id.
                                               Module libpcre2-8.so.0 without build-id.
                                               Module libffi.so.8 without build-id.
                                               Module libcap.so.2 without build-id.
                                               Module libgudev-1.0.so.0 without build-id.
                                               Module libXdmcp.so.6 without build-id.
                                               Module libXau.so.6 without build-id.
                                               Module libxcb.so.1 without build-id.
                                               Module libjson-glib-1.0.so.0 without build-id.
                                               Module libaccountsservice.so.0 without build-id.
                                               Stack trace of thread 1738:
                                               #0  0x00007f8c3c0e69bb g_logv (libglib-2.0.so.0 + 0x6f9bb)
                                               #1  0x00007f8c3c0e6c2f g_log (libglib-2.0.so.0 + 0x6fc2f)
                                               #2  0x000055ff5aa2a42b get_fallback_session_name (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x4742b)
                                               #3  0x000055ff5aa2f261 gdm_session_session_registers (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x4c261)
                                               #4  0x000055ff5aa2f888 gdm_session_start_session (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x4c888)
                                               #5  0x00007f8c3bcc8052 ffi_call_unix64 (libffi.so.8 + 0xa052)
                                               #6  0x00007f8c3bcc660d ffi_call_int (libffi.so.8 + 0x860d)
                                               #7  0x00007f8c3bcc75ae ffi_call (libffi.so.8 + 0x95ae)
                                               #8  0x00007f8c3c1f15b3 g_cclosure_marshal_generic_va (libgobject-2.0.so.0 + 0x195b3)
                                               #9  0x00007f8c3c1f0731 _g_closure_invoke_va (libgobject-2.0.so.0 + 0x18731)
                                               #10 0x00007f8c3c207af2 signal_emit_valist_unlocked (libgobject-2.0.so.0 + 0x2faf2)
                                               #11 0x00007f8c3c20d7ed g_signal_emit_valist (libgobject-2.0.so.0 + 0x357ed)
                                               #12 0x00007f8c3c20d8bf g_signal_emit (libgobject-2.0.so.0 + 0x358bf)
                                               #13 0x000055ff5aa2c7f8 on_opened (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x497f8)
                                               #14 0x00007f8c3bec9dcc g_task_return_now (libgio-2.0.so.0 + 0xc9dcc)
                                               #15 0x00007f8c3becac83 g_task_return (libgio-2.0.so.0 + 0xcac83)
                                               #16 0x00007f8c3bf3e8f3 reply_cb (libgio-2.0.so.0 + 0x13e8f3)
                                               #17 0x00007f8c3bec9dcc g_task_return_now (libgio-2.0.so.0 + 0xc9dcc)
                                               #18 0x00007f8c3becac83 g_task_return (libgio-2.0.so.0 + 0xcac83)
                                               #19 0x00007f8c3bf30752 g_dbus_connection_call_done (libgio-2.0.so.0 + 0x130752)
                                               #20 0x00007f8c3bec9dcc g_task_return_now (libgio-2.0.so.0 + 0xc9dcc)
                                               #21 0x00007f8c3bec9e01 complete_in_idle_cb (libgio-2.0.so.0 + 0xc9e01)
                                               #22 0x00007f8c3c0d7949 g_idle_dispatch (libglib-2.0.so.0 + 0x60949)
                                               #23 0x00007f8c3c0d99ed g_main_context_dispatch_unlocked (libglib-2.0.so.0 + 0x629ed)
                                               #24 0x00007f8c3c0dce78 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65e78)
                                               #25 0x00007f8c3c0dd967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #26 0x000055ff5a9f7807 main (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x14807)
                                               #27 0x00007f8c3ba2a4d8 __libc_start_call_main (libc.so.6 + 0x2a4d8)
                                               #28 0x00007f8c3ba2a59b __libc_start_main@@GLIBC_2.34 (libc.so.6 + 0x2a59b)
                                               #29 0x000055ff5a9f7a75 _start (/nix/store/w7fl1l8dzxmf4d8725k4vcb1inzl6c2k-gdm-49.2/bin/gdm + 0x14a75)
                                               
                                               Stack trace of thread 1748:
                                               #0  0x00007f8c3bb208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007f8c3c110610 g_cond_wait_until (libglib-2.0.so.0 + 0x99610)
                                               #2  0x00007f8c3c0a0c6b g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29c6b)
                                               #3  0x00007f8c3c11110a g_thread_pool_thread_proxy (libglib-2.0.so.0 + 0x9a10a)
                                               #4  0x00007f8c3c11089d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f8c3ba9a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f8c3bb22d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1740:
                                               #0  0x00007f8c3bb208bd syscall (libc.so.6 + 0x1208bd)
                                               #1  0x00007f8c3c110129 g_cond_wait (libglib-2.0.so.0 + 0x99129)
                                               #2  0x00007f8c3c0a0cab g_async_queue_pop_intern_unlocked (libglib-2.0.so.0 + 0x29cab)
                                               #3  0x00007f8c3c110b8f g_thread_pool_spawn_thread (libglib-2.0.so.0 + 0x99b8f)
                                               #4  0x00007f8c3c11089d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f8c3ba9a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f8c3bb22d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1742:
                                               #0  0x00007f8c3bb14a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f8c3c0dcf68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f8c3c0dd967 g_main_loop_run (libglib-2.0.so.0 + 0x66967)
                                               #3  0x00007f8c3bf4180e gdbus_shared_thread_func (libgio-2.0.so.0 + 0x14180e)
                                               #4  0x00007f8c3c11089d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f8c3ba9a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f8c3bb22d2c __clone3 (libc.so.6 + 0x122d2c)
                                               
                                               Stack trace of thread 1741:
                                               #0  0x00007f8c3bb14a10 ppoll (libc.so.6 + 0x114a10)
                                               #1  0x00007f8c3c0dcf68 g_main_context_iterate_unlocked.isra.0 (libglib-2.0.so.0 + 0x65f68)
                                               #2  0x00007f8c3c0dd70f g_main_context_iteration (libglib-2.0.so.0 + 0x6670f)
                                               #3  0x00007f8c3c0dd761 glib_worker_main (libglib-2.0.so.0 + 0x66761)
                                               #4  0x00007f8c3c11089d g_thread_proxy (libglib-2.0.so.0 + 0x9989d)
                                               #5  0x00007f8c3ba9a97a start_thread (libc.so.6 + 0x9a97a)
                                               #6  0x00007f8c3bb22d2c __clone3 (libc.so.6 + 0x122d2c)
                                               ELF object binary architecture: AMD x86-64
Dez 10 02:58:51 laptop systemd[1]: Failed to start Display Manager.

Can someone help me here, because I don’t really know what to do/try next or how to get to the ground of things. Am I nearly the only one with this behaviour?

Thank you for taking the time to read through this!

2

Looks like it’s still trying to start the x11 version, which should indeed not exist.

Was the activation successful? Do you have any custom activation scripts? What do the rest of your config and logs look like?

3

Thank you for your response.

The rest of my config is:

{ config, pkgs, ... }:

{
  imports = [
    # Include the results of the hardware scan.
    ./hardware-configuration.nix
    ../default-configuration.nix
  ];

  # Bootloader.
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  # Enable firmware updates.
  services.fwupd.enable = true;

  networking.hostName = xyz; # Define your hostname.

  # Enable networking
  networking.networkmanager.enable = true;

  # Set your time zone.
  time.timeZone = "Europe/Berlin";

  # Select internationalisation properties.
  i18n.defaultLocale = "en_GB.UTF-8";

  i18n.extraLocaleSettings = {
    LC_ADDRESS = "de_DE.UTF-8";
    LC_IDENTIFICATION = "de_DE.UTF-8";
    LC_MEASUREMENT = "de_DE.UTF-8";
    LC_MONETARY = "de_DE.UTF-8";
    LC_NAME = "de_DE.UTF-8";
    LC_NUMERIC = "de_DE.UTF-8";
    LC_PAPER = "de_DE.UTF-8";
    LC_TELEPHONE = "de_DE.UTF-8";
    LC_TIME = "de_DE.UTF-8";
  };

  # Enable the GNOME Desktop Environment.
  services.displayManager.gdm.enable = true;
  services.desktopManager.gnome.enable = true;

  # Configure keymap in X11
  services.xserver.xkb = {
    layout = "de";
    variant = "";
  };

  # Configure console keymap
  console.keyMap = "de";

  # Enable CUPS to print documents.
  services.printing.enable = true;

  services.libinput.enable = true;

  # Define a user account. Don't forget to set a password with ‘passwd’.
  users.users.xyz = {
    isNormalUser = true;
    description = xyz;
    extraGroups = [
      "networkmanager"
      "wheel"
      "dialout"
    ];
  };
  # allow unfree packages
  nixpkgs.config.allowUnfree = true;

}

and in another file for some common packages and settings:

{ pkgs, inputs, ... }:

{
  # Setting zsh as the default shell
  users.defaultUserShell = pkgs.zsh;
  programs.zsh.enable = true;

  # Enable OpenGL
  hardware.graphics = {
    enable = true;
  };

  # Install jetbrains-mono font
  fonts.packages = [ pkgs.nerd-fonts.jetbrains-mono ];
  fonts.fontDir.enable = true;

  environment.sessionVariables = {
    XDG_SESSION_TYPE = "x11";
  };
  nix.nixPath = [ "nixpkgs=${inputs.nixpkgs}" ];

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment.systemPackages = with pkgs; [
    ######### Utilities ##########
    alacritty # Terminal emulator
    wget # download utility for the command line
    curl # download utility for the command line
    jq # JSON processing tool
    tree # Nice way to display the directory and file structure
    zip # Zip utility to compress files/folders to .zip
    unzip # Unzip utility to decompress .zip files/folders
    musl # Standard library for C for static linking
    git # Version management for files (or Code)
    gcc # linux standard compiler collection
    parallel # gnu parallel for parallel shell execution
    vivaldi # Browser focused on privacy
    coreutils # GNU core utilities
  ];

  # Setting evince to be the default app to view pdf
  xdg.mime = {
    enable = true;
    addedAssociations = {
      "application/pdf" = "org.gnome.Papers.desktop";
    };
  };

  programs.java = {
    enable = true;
    package = (pkgs.zulu25.override { enableJavaFX = true; });
  };

  programs.steam = {
    enable = true;
    remotePlay.openFirewall = true; # Open ports in the firewall for Steam Remote Play
    dedicatedServer.openFirewall = true; # Open ports in the firewall for Source Dedicated Server
    localNetworkGameTransfers.openFirewall = true; # Open ports in the firewall for Steam Local Network Game Transfers
  };

  # Some programs need SUID wrappers, can be configured further or are
  # started in user sessions.
  # programs.mtr.enable = true;
  programs.gnupg.agent = {
    enable = true;
    enableSSHSupport = true;
  };

  programs.direnv = {
    enable = true;
    nix-direnv.enable = true;
  };

  # List services that you want to enable:

  # Enable the OpenSSH daemon.
  # services.openssh.enable = true;

  # Open ports in the firewall.
  # networking.firewall.allowedTCPPorts = [ ... ];
  # networking.firewall.allowedUDPPorts = [ ... ];
  # Or disable the firewall altogether.
  # networking.firewall.enable = false;

  # This value determines the NixOS release from which the default
  # settings for stateful data, like file locations and database versions
  # on your system were taken. It‘s perfectly fine and recommended to leave
  # this value at the release version of the first install of this system.
  # Before changing this value read the documentation for this option
  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
  system.stateVersion = "25.11"; # Did you read the comment?

  nix.settings.experimental-features = [
    "nix-command"
    "flakes"
  ];
}

What do you mean with the activation or how do i check if it was successful?
I do not have any custom activation scripts.

4

I wonder if removing this is enough to fix it.

Gnome no longer ships with an X11 session, you have to use wayland if you want to use gnome.

5

Thank you so much!

Holy **** I really struggled on this.
It works now!

So just for my understanding:
gnome ships with wayland but still asks the environment variables. So if it sees X11 it forcefully tries to instantiate X11 at some entry point that does not exist anymore ?

6

I’m not 100% certain, but something along those lines. Even if login did work, setting that variable would likely cause lots of other issues with applications that try to figure out whether to render against X11 or wayland.

I suspect this particular issue is gdm’s fault, which I believe hasn’t moved to wayland yet since launching X11 desktops requires already being in an X11 session and gdm technically supports launching non-gnome desktops. It probably has some hard-coded path for launching an X11 gnome that still exists in case you did install a legacy version, but the x11 gnome target no longer does on NixOS as of 25.11.

But I don’t use gdm/gnome and I don’t know their session init flow very well, so my guess is as good as yours.

7

Ah ok thats interesting.
Thank you so much for taking the time!