Show IP in login prompt (?)

[davidak]

Issue description

I have a NixOS installation without graphical user interface and use DHCP to get an IP.

I have power, ethernet and a display connected to the device.

To connect via ssh, i have to connect a keyboard and type the password to login and get the IP.

It would be helpful to see the primary IP in login prompt!

It's probably not that easy to get the primary IP. On traditional systems the NIC is called eth0, but with systemd, it's called differently on every system. In my case, i use a bridge called br0.

For my nixos-containers, i use ip -4 addr show eth0 | grep -oP '(?<=inet\s)\d+(\.\d+){3}' to get the IP.

The login help text seem to be defined here: https://github.com/NixOS/nixpkgs/blob/release-19.03/nixos/modules/services/ttys/agetty.nix

Technical details

• system: "x86_64-linux"
• host os: Linux 4.19.46, NixOS, 19.03.172758.36516712916 (Koi)
• multi-user?: yes
• sandbox: yes
• version: nix-env (Nix) 2.2.2
• channels(root): "nixos-19.03.172883.1601f559e89"
• nixpkgs: /nix/var/nix/profiles/per-user/root/channels/nixos

[cleverca22]

my typical solution to this is to services.avahi.enable = true; and then run avahi-browse -at on another machine to list all avahi machines on the LAN

[gloaming]

This is already supported by agetty(8):

ISSUE FILES

       The default issue file is /etc/issue. If the file exists then agetty
       also checks for /etc/issue.d directory. The directory is optional
       extension to the default issue file and content of the directory is
       printed after /etc/issue content. If the /etc/issue does not exist
       than the directory is ignored. All files with .issue extension from
       the directory are printed in version-sort order. The directory allow
       to maintain 3rd-party messages independently on the primary system
       /etc/issue file.

       The default path maybe overridden by --issue-file option. In this
       case specified path has to be file or directory and the default
       /etc/issue as well as /etc/issue.d are ignored.

       The issue files may contain certain escape codes to display the
       system name, date, time etcetera.  All escape codes consist of a
       backslash (\) immediately followed by one of the characters listed
       below.

       4 or 4{interface}
              Insert the IPv4 address of the specified network interface
              (for example: \4{eth0}).  If the interface argument is not
              specified, then select the first fully configured (UP, non-
              LOCALBACK, RUNNING) interface.  If not any configured
              interface is found, fall back to the IP address of the
              machine's hostname.

But there's no guarantee that DHCP has assigned an address when it runs, and the IP might change later, so you'll want to do

  environment.etc."issue.d/ip.issue".text = "\\4\n";
  networking.dhcpcd.runHook = "${pkgs.utillinux}/bin/agetty --reload";

Which works on my machine.
But this seems like an odd thing to do. Why don't you just configure a static IP?

[mmahut]

Are any other linux distributions that are doing this? I know some of the *BSD did, but not sure about linux.

[stale]

Thank you for your contributions.

This has been automatically marked as stale because it has had no activity for 180 days.

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[davidak]

#63322 (comment) works. The login took longer to appear.

Should we make this a NixOS option (enableIP...) or just document it (where? wiki?)?

[stale]

I marked this as stale due to inactivity. → More info

[573]

Still interested in this.

[davidak]

@573 what solution would you like to have?

[573]

I guess I would prefer to have it as a NixOS option.