Add initial installer
This commit is contained in:
215
nixos/modules/tmproot.nix
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215
nixos/modules/tmproot.nix
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{ lib, pkgs, config, ... }:
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let
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inherit (lib) optionalString concatStringsSep concatMap concatMapStringsSep mkIf mkDefault mkMerge mkVMOverride;
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inherit (lib.my) mkOpt' mkBoolOpt' mkVMOverride';
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cfg = config.my.tmproot;
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enablePersistence = cfg.persistDir != null;
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showUnsaved =
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''
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#!${pkgs.python310}/bin/python
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import stat
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import sys
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import os
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ignored = [
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${concatStringsSep ",\n " (map (p: "'${p}'") cfg.unsaved.ignore)}
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]
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base = '/'
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base_dev = os.stat(base).st_dev
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def recurse(p, link=None):
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try:
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for ignore in ignored:
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if p.startswith(ignore):
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return
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st = os.lstat(p)
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if st.st_dev != base_dev:
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return
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if stat.S_ISLNK(st.st_mode):
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target = os.path.realpath(p, strict=False)
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if os.access(target, os.F_OK):
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recurse(target, link=p)
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return
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elif stat.S_ISDIR(st.st_mode):
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for e in os.listdir(p):
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recurse(os.path.join(p, e))
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return
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print(link or p)
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except PermissionError as ex:
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print(f'{p}: {ex.strerror}', file=sys.stderr)
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recurse(base)
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'';
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rootDef = {
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device = "yeet";
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fsType = "tmpfs";
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options = [ "size=${cfg.size}" ];
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};
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in
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{
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options = with lib.types; {
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my.tmproot = {
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enable = mkBoolOpt' true "Whether to enable tmproot.";
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persistDir = mkOpt' (nullOr str) "/persist" "Path where persisted files are stored.";
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size = mkOpt' str "2G" "Size of tmpfs root";
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unsaved = {
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showMotd = mkBoolOpt' true "Whether to show unsaved files with `dynamic-motd`.";
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ignore = mkOpt' (listOf str) [ ] "Path prefixes to ignore if unsaved.";
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};
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};
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};
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config = mkIf cfg.enable (mkMerge [
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{
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assertions = [
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{
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# I mean you probably _could_, but if you're doing tmproot... come on
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assertion = !config.users.mutableUsers;
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message = "users.mutableUsers is incompatible with tmproot";
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}
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];
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my.tmproot.unsaved.ignore = [
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"/tmp"
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# setup-etc.pl will create this for us
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"/etc/NIXOS"
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# Once mutableUsers is disabled, we should be all clear here
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"/etc/passwd"
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"/etc/group"
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"/etc/shadow"
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"/etc/subuid"
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"/etc/subgid"
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# Lock file for /etc/{passwd,shadow}
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"/etc/.pwd.lock"
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# systemd last updated? I presume they'll get updated on boot...
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"/etc/.updated"
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"/var/.updated"
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# Specifies obsolete files that should be deleted on activation - we'll never have those!
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"/etc/.clean"
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];
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environment.systemPackages = [
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(pkgs.writeScriptBin "tmproot-unsaved" showUnsaved)
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];
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my.dynamic-motd.script = mkIf cfg.unsaved.showMotd
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''
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tmprootUnsaved() {
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local count="$(tmproot-unsaved | wc -l)"
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[ $count -eq 0 ] && return
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echo
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echo -e "\t\e[31;1;4mWarning:\e[0m $count file(s) on / will be lost on shutdown!"
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echo -e '\tTo see them, run `tmproot-unsaved` as root.'
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${optionalString enablePersistence ''
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echo -e '\tAdd these files to `environment.persistence."${cfg.persistDir}"` to keep them!'
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''}
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echo -e "\tIf they don't need to be kept, add them to \`my.tmproot.unsaved.ignore\`."
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echo
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}
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tmprootUnsaved
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'';
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fileSystems."/" = rootDef;
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}
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(mkIf config.networking.resolvconf.enable {
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my.tmproot.unsaved.ignore = [ "/etc/resolv.conf" ];
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})
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(mkIf config.security.doas.enable {
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my.tmproot.unsaved.ignore = [ "/etc/doas.conf" ];
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})
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(mkIf config.my.build.isDevVM {
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my.tmproot.unsaved.ignore = [ "/nix" ];
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fileSystems = mkVMOverride {
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"/" = mkVMOverride' rootDef;
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};
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})
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(mkIf enablePersistence (mkMerge [
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{
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assertions = [
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{
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assertion = config.fileSystems ? "${cfg.persistDir}";
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message = "The 'fileSystems' option does not specify your persistence file system (${cfg.persistDir}).";
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}
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];
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# Catch non-existent source directories that are needed for boot (see `pathsNeededForBoot` in
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# nixos/lib/util.nix). We do this by monkey-patching the `waitDevice` function that would otherwise hang.
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boot.initrd.postDeviceCommands =
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''
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ensurePersistSource() {
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[ -e "/mnt-root$1" ] && return
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echo "Persistent source directory $1 does not exist, creating..."
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install -dm "$2" "/mnt-root$1" || fail
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}
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_waitDevice() {
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local device="$1"
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${concatMapStringsSep " || \\\n " (d:
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let
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sourceDir = "${d.persistentStoragePath}${d.directory}";
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in
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''([ "$device" = "/mnt-root${sourceDir}" ] && ensurePersistSource "${sourceDir}" "${d.mode}")'')
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config.environment.persistence."${cfg.persistDir}".directories}
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waitDevice "$@"
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}
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type waitDevice > /dev/null || (echo "waitDevice is missing!"; fail)
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alias waitDevice=_waitDevice
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'';
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environment.persistence."${cfg.persistDir}" = {
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hideMounts = mkDefault true;
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directories = [
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"/var/log"
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# In theory we'd include only the files needed individually (i.e. the {U,G}ID map files that track deleted
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# users and groups), but `update-users-groups.pl` actually deletes the original files for "atomic update".
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# Also the script runs before impermanence does.
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"/var/lib/nixos"
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"/var/lib/systemd"
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];
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files = [
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"/etc/machine-id"
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];
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};
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virtualisation = {
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diskImage = "./.vms/${config.system.name}-persist.qcow2";
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};
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}
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(mkIf config.services.openssh.enable {
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environment.persistence."${cfg.persistDir}".files =
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concatMap (k: [ k.path "${k.path}.pub" ]) config.services.openssh.hostKeys;
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})
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(mkIf config.my.build.isDevVM {
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fileSystems = mkVMOverride {
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# Hijack the "root" device for persistence in the VM
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"${cfg.persistDir}" = {
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device = config.virtualisation.bootDevice;
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neededForBoot = true;
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};
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};
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})
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]))
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]);
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meta.buildDocsInSandbox = false;
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}
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