nixos-generate-config: Detect btrfs subvolumes

2 files changed, 22 insertions, 0 deletions

diff --git a/nixos/modules/installer/tools/nixos-generate-config.pl b/nixos/modules/installer/tools/nixos-generate-config.pl
index 66a8152a3a6cc..cabdb09ec9c18 100644
--- a/nixos/modules/installer/tools/nixos-generate-config.pl
+++ b/nixos/modules/installer/tools/nixos-generate-config.pl
@@ -20,6 +20,13 @@ sub uniq {
     return @res;
 }
 
+sub runCommand {
+    my ($cmd) = @_;
+    open FILE, "$cmd 2>/dev/null |" or die "Failed to execute: $cmd\n";
+    my @ret = <FILE>;
+    close FILE;
+    return ($?, @ret);
+}
 
 # Process the command line.
 my $outDir = "/etc/nixos";
@@ -337,6 +344,20 @@ EOF
         }
     }
 
+	# Is this a btrfs filesystem?
+	if ($fsType eq "btrfs") {
+		my ($status, @info) = runCommand("btrfs subvol show $rootDir$mountPoint");
+		if ($status != 0) {
+			die "Failed to retreive subvolume info for $mountPoint";
+		}
+		my @subvols = join("", @info) =~ m/Name:[ \t\n]*([^ \t\n]*)/;
+		if ($#subvols > 0) {
+			die "Btrfs subvol name for $mountPoint listed multiple times in mount\n"
+		} elsif ($#subvols == 0) {
+			push @extraOptions, "subvol=$subvols[0]";
+		}
+	}
+
     # Emit the filesystem.
     $fileSystems .= <<EOF;
   fileSystems.\"$mountPoint\" =
diff --git a/nixos/modules/installer/tools/tools.nix b/nixos/modules/installer/tools/tools.nix
index 39da2f1f0be6b..91a30695a7a54 100644
--- a/nixos/modules/installer/tools/tools.nix
+++ b/nixos/modules/installer/tools/tools.nix
@@ -38,6 +38,7 @@ let
   nixos-generate-config = makeProg {
     name = "nixos-generate-config";
     src = ./nixos-generate-config.pl;
+    path = [ pkgs.btrfsProgs ];
     perl = "${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/lib/perl5/site_perl";
   };