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2710a49adb
On Linux we cannot feasbibly generate users statically because we need to take care to not change or re-use UIDs over the lifetime of a machine (i.e. over multiple generations). This means we need the context of the running machine. Thus, stop creating users statically and instead generate them at runtime irrespective of mutableUsers. When /etc is immutable, the password files (e.g. /etc/passwd etc.) are created in a separate directory (/var/lib/nixos/etc). /etc will be pre-populated with symlinks to this separate directory. Immutable users are now implemented by bind-mounting the password files read-only onto themselves and only briefly re-mounting them writable to re-execute sysusers. The biggest limitation of this design is that you now need to manually unmount this bind mount to change passwords because sysusers cannot change passwords for you. This shouldn't be too much of an issue because system users should only rarely need to change their passwords.
67 lines
2.5 KiB
Nix
67 lines
2.5 KiB
Nix
{ lib, ... }: {
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name = "activation-etc-overlay-immutable";
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meta.maintainers = with lib.maintainers; [ nikstur ];
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nodes.machine = { pkgs, ... }: {
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system.etc.overlay.enable = true;
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system.etc.overlay.mutable = false;
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# Prerequisites
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systemd.sysusers.enable = true;
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users.mutableUsers = false;
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boot.initrd.systemd.enable = true;
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boot.kernelPackages = pkgs.linuxPackages_latest;
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time.timeZone = "Utc";
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environment.etc = {
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"mountpoint/.keep".text = "keep";
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"filemount".text = "keep";
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};
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specialisation.new-generation.configuration = {
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environment.etc."newgen".text = "newgen";
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};
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};
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testScript = ''
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with subtest("/etc is mounted as an overlay"):
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machine.succeed("findmnt --kernel --type overlay /etc")
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with subtest("direct symlinks point to the target without indirection"):
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assert machine.succeed("readlink -n /etc/localtime") == "/etc/zoneinfo/Utc"
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with subtest("Correct mode on the source password files"):
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assert machine.succeed("stat -c '%a' /var/lib/nixos/etc/passwd") == "644\n"
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assert machine.succeed("stat -c '%a' /var/lib/nixos/etc/group") == "644\n"
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assert machine.succeed("stat -c '%a' /var/lib/nixos/etc/shadow") == "0\n"
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assert machine.succeed("stat -c '%a' /var/lib/nixos/etc/gshadow") == "0\n"
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with subtest("Password files are symlinks to /var/lib/nixos/etc"):
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assert machine.succeed("readlink -f /etc/passwd") == "/var/lib/nixos/etc/passwd\n"
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assert machine.succeed("readlink -f /etc/group") == "/var/lib/nixos/etc/group\n"
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assert machine.succeed("readlink -f /etc/shadow") == "/var/lib/nixos/etc/shadow\n"
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assert machine.succeed("readlink -f /etc/gshadow") == "/var/lib/nixos/etc/gshadow\n"
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with subtest("switching to the same generation"):
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machine.succeed("/run/current-system/bin/switch-to-configuration test")
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with subtest("switching to a new generation"):
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machine.fail("stat /etc/newgen")
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machine.succeed("mount -t tmpfs tmpfs /etc/mountpoint")
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machine.succeed("touch /etc/mountpoint/extra-file")
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machine.succeed("mount --bind /dev/null /etc/filemount")
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machine.succeed("/run/current-system/specialisation/new-generation/bin/switch-to-configuration switch")
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assert machine.succeed("cat /etc/newgen") == "newgen"
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print(machine.succeed("findmnt /etc/mountpoint"))
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print(machine.succeed("ls /etc/mountpoint"))
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print(machine.succeed("stat /etc/mountpoint/extra-file"))
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print(machine.succeed("findmnt /etc/filemount"))
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'';
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}
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