Merge pull request #206839 from lheckemann/stateless-vms
nixos/qemu-vm: allow use without a disk image
This commit is contained in:
commit
48269da315
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@ -108,9 +108,9 @@ let
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set -e
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NIX_DISK_IMAGE=$(readlink -f "''${NIX_DISK_IMAGE:-${config.virtualisation.diskImage}}")
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NIX_DISK_IMAGE=$(readlink -f "''${NIX_DISK_IMAGE:-${toString config.virtualisation.diskImage}}") || test -z "$NIX_DISK_IMAGE"
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if ! test -e "$NIX_DISK_IMAGE"; then
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if test -n "$NIX_DISK_IMAGE" && ! test -e "$NIX_DISK_IMAGE"; then
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${qemu}/bin/qemu-img create -f qcow2 "$NIX_DISK_IMAGE" \
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${toString config.virtualisation.diskSize}M
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fi
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@ -346,7 +346,7 @@ in
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virtualisation.diskImage =
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mkOption {
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type = types.str;
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type = types.nullOr types.str;
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default = "./${config.system.name}.qcow2";
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defaultText = literalExpression ''"./''${config.system.name}.qcow2"'';
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description =
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@ -354,6 +354,9 @@ in
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Path to the disk image containing the root filesystem.
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The image will be created on startup if it does not
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exist.
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If null, a tmpfs will be used as the root filesystem and
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the VM's state will not be persistent.
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'';
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};
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@ -990,12 +993,12 @@ in
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];
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virtualisation.qemu.drives = mkMerge [
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[{
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(mkIf (cfg.diskImage != null) [{
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name = "root";
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file = ''"$NIX_DISK_IMAGE"'';
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driveExtraOpts.cache = "writeback";
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driveExtraOpts.werror = "report";
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}]
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}])
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(mkIf cfg.useNixStoreImage [{
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name = "nix-store";
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file = ''"$TMPDIR"/store.img'';
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@ -1018,20 +1021,21 @@ in
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}) cfg.emptyDiskImages)
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];
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fileSystems = mkVMOverride cfg.fileSystems;
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# Mount the host filesystem via 9P, and bind-mount the Nix store
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# of the host into our own filesystem. We use mkVMOverride to
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# allow this module to be applied to "normal" NixOS system
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# configuration, where the regular value for the `fileSystems'
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# attribute should be disregarded for the purpose of building a VM
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# test image (since those filesystems don't exist in the VM).
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fileSystems =
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let
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virtualisation.fileSystems = let
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mkSharedDir = tag: share:
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{
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name =
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if tag == "nix-store" && cfg.writableStore
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then "/nix/.ro-store"
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else share.target;
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then "/nix/.ro-store"
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else share.target;
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value.device = tag;
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value.fsType = "9p";
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value.neededForBoot = true;
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@ -1039,44 +1043,42 @@ in
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[ "trans=virtio" "version=9p2000.L" "msize=${toString cfg.msize}" ]
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++ lib.optional (tag == "nix-store") "cache=loose";
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};
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in
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mkVMOverride (cfg.fileSystems //
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optionalAttrs cfg.useDefaultFilesystems {
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"/".device = cfg.bootDevice;
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"/".fsType = "ext4";
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"/".autoFormat = true;
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} //
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optionalAttrs config.boot.tmpOnTmpfs {
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"/tmp" = {
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in lib.mkMerge [
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(lib.mapAttrs' mkSharedDir cfg.sharedDirectories)
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{
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"/" = lib.mkIf cfg.useDefaultFilesystems (if cfg.diskImage == null then {
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device = "tmpfs";
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fsType = "tmpfs";
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} else {
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device = cfg.bootDevice;
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fsType = "ext4";
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autoFormat = true;
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});
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"/tmp" = lib.mkIf config.boot.tmpOnTmpfs {
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device = "tmpfs";
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fsType = "tmpfs";
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neededForBoot = true;
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# Sync with systemd's tmp.mount;
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options = [ "mode=1777" "strictatime" "nosuid" "nodev" "size=${toString config.boot.tmpOnTmpfsSize}" ];
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};
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} //
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optionalAttrs cfg.useNixStoreImage {
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"/nix/${if cfg.writableStore then ".ro-store" else "store"}" = {
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"/nix/${if cfg.writableStore then ".ro-store" else "store"}" = lib.mkIf cfg.useNixStoreImage {
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device = "${lookupDriveDeviceName "nix-store" cfg.qemu.drives}";
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neededForBoot = true;
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options = [ "ro" ];
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};
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} //
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optionalAttrs (cfg.writableStore && cfg.writableStoreUseTmpfs) {
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"/nix/.rw-store" = {
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"/nix/.rw-store" = lib.mkIf (cfg.writableStore && cfg.writableStoreUseTmpfs) {
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fsType = "tmpfs";
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options = [ "mode=0755" ];
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neededForBoot = true;
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};
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} //
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optionalAttrs cfg.useBootLoader {
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# see note [Disk layout with `useBootLoader`]
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"/boot" = {
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"/boot" = lib.mkIf cfg.useBootLoader {
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device = "${lookupDriveDeviceName "boot" cfg.qemu.drives}2"; # 2 for e.g. `vdb2`, as created in `bootDisk`
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fsType = "vfat";
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noCheck = true; # fsck fails on a r/o filesystem
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};
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} // lib.mapAttrs' mkSharedDir cfg.sharedDirectories);
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}
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];
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boot.initrd.systemd = lib.mkIf (config.boot.initrd.systemd.enable && cfg.writableStore) {
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mounts = [{
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