Nixos-rebuild fails due to home-manager

Help
1

My nixos-rebuild fails because it cannot restart home-manager-klt.service.
The error help suggest to Move or remove the above files and try again.
However I do not see any file names.

Here the output

➜ sudo nix-channel --list

home-manager https://github.com/nix-community/home-manager/archive/release-25.05.tar.gz
nixos https://nixos.org/channels/nixos-25.05

➜ sudo nixos-rebuild switch

building Nix...
building the system configuration...
evaluation warning: substituteAll is deprecated and will be removed in 25.11. Use replaceVars instead.
activating the configuration...
setting up /etc...
reloading user units for klt...
restarting sysinit-reactivation.target
the following new units were started: NetworkManager-dispatcher.service
warning: the following units failed: home-manager-klt.service
× home-manager-klt.service - Home Manager environment for klt
     Loaded: loaded (/etc/systemd/system/home-manager-klt.service; enabled; preset: ignored)
     Active: failed (Result: exit-code) since Fri 2025-08-01 08:26:41 CEST; 472ms ago
 Invocation: 4811641be7e446ad99db7607b638d9fe
    Process: 11447 ExecStart=/nix/store/d6mhq77jyaidz98k11wj0xragdkmw1a0-hm-setup-env /nix/store/f4qkz7fa17xcm4lvlx92yvd89j1cln9y-home-manager-generation (code=exited, status=1/FAILURE)
   Main PID: 11447 (code=exited, status=1/FAILURE)
         IP: 0B in, 0B out
         IO: 0B read, 0B written
   Mem peak: 6M
        CPU: 129ms

Aug 01 08:26:41 maxiTower hm-activate-klt[11629]: Please do one of the following:
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]: - Move or remove the above files and try again.
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]: - In standalone mode, use 'home-manager switch -b backup' to back up
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]:   files automatically.
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]: - When used as a NixOS or nix-darwin module, set
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]:     'home-manager.backupFileExtension'
Aug 01 08:26:41 maxiTower hm-activate-klt[11629]:   to, for example, 'backup' and rebuild.
Aug 01 08:26:41 maxiTower systemd[1]: home-manager-klt.service: Main process exited, code=exited, status=1/FAILURE
Aug 01 08:26:41 maxiTower systemd[1]: home-manager-klt.service: Failed with result 'exit-code'.
Aug 01 08:26:41 maxiTower systemd[1]: Failed to start Home Manager environment for klt.
warning: error(s) occurred while switching to the new configuration

Has anyone an idea what to do?

I import home-manager into my configuration.nix:

  imports = [
    # Include the results of the hardware scan.
    ./hardware-configuration.nix

...

    # Include Home Manager Config
    ./home.nix
    # Update PostGre
    # ./postgresUpdateScript.nix
  ] ++ prop.specificImports;
2

Systemd doesn’t show enough of the log by default to see the file names. Check systemctl status -n100 home-manager-klt.service to see (probably) the full log.

3

Or allow home-manger to create a backup file, then the error will not occur again in the future!

home-manager.backupFileExtension = "hm.OLD"; # Automatic backup of conflicting configuration files.
4

I believe it still fails if the backup file already exists in that case, so it’s not all that useful, as you still need to do something manually to avoid problems.

5

It’s not true, you will have to manually delete the existing backup then once the config is updated and rebuilt the backup files work. Had this happen to me and I just added the line like @DocBrown101 show’d and it worked.

Edit: my bad, misread your comment, you’re right manual intervention is required as you said. Sorry.

6

My mistake:
I have installed software from MicroSoft:

➜  ~ systemctl status -n100 home-manager-klt.service
...
Aug 10 13:13:42 maxiTower hm-activate-klt[100536]: Existing file '/home/klt/.config/teams-for-linux/Preferences.backup' would be clobbered by backing up '/home/klt/.config/teams-for-linux/Preferences'

but I need Teams for my work :rage:

I do not like to back up automatically, because there might be cases when I want to keep the original file. Moreover would I see which config files have been back upped?

Nevertheless, the command systemctl status home-manager-klt.service should not say Move or remove the above files and try again without showing any files. I understand that there are different levels of verbosity but each should be consistent.

7

A PR improving this has recently been merged, though not yet backported to HM 25.05.

HM does not intentionally truncate this output or hide the files behind any sort of a verbosity level It is simply an effect of it shelling out to systemctl status which by default only lists a small amount of log output for the unit.

1 Like