* Allow swap devices to be specified by label.

svn path=/nixos/trunk/; revision=7609

configuration/examples/basic.nix

@@ -9,7 +9,9 @@
     }
   ];
 
-  swapDevices = ["/dev/sdb1"];
+  swapDevices = [
+    { device = "/dev/sdb1"; }
+  ];
   
   services = {
     sshd = {

system/options.nix

@@ -212,10 +212,19 @@
   {
     name = ["swapDevices"];
     default = [];
-    example = ["/dev/hda7" "/dev/hdb3" "/var/swapfile"];
+    example = [
+      {device="/dev/hda7";}
+      {device="/var/swapfile";}
+      {label="bigswap";}
+    ];
     description = "
       The swap devices and swap files.  These must have been
-      initialised using <command>mkswap</command>.
+      initialised using <command>mkswap</command>.  Each element
+      should be an attribute set specifying either the path of the
+      swap device or file (<literal>device</literal>) or the label
+      of the swap device (<literal>label</literal>, see
+      <command>mkswap -L</command</command>).  Using a label is
+      recommended.
     ";
   }
 

system/upstart.nix

@@ -46,7 +46,7 @@ import ../upstart-jobs/gather.nix {
 
     # Swapping.
     (import ../upstart-jobs/swap.nix {
-      inherit (pkgs) utillinux;
+      inherit (pkgs) utillinux library;
       swapDevices = config.get ["swapDevices"];
     })
 

upstart-jobs/swap.nix

@@ -1,4 +1,14 @@
-{utillinux, swapDevices}:
+{library, utillinux, swapDevices}:
+
+let
+
+  devicesByPath =
+    map (x: x.device) (library.filter (x: x ? device) swapDevices);
+    
+  devicesByLabel =
+    map (x: x.label) (library.filter (x: x ? label) swapDevices);
+
+in
 
 {
   name = "swap";
@@ -8,21 +18,25 @@ start on startup
 start on new-devices
 
 script
-    for device in ${toString swapDevices}; do
-        # !!! Check whether we are already swapping to $device.
+    for device in ${toString devicesByPath}; do
         ${utillinux}/sbin/swapon \"$device\" || true
     done
 
-    # Remove swap devices not listed in swapDevices.
-    for used in $(cat /proc/swaps | grep '^/' | sed 's/ .*//'); do
-        found=
-        for device in ${toString swapDevices}; do
-            if test \"$used\" = \"$device\"; then found=1; fi
-        done
-        if test -z \"$found\"; then
-            ${utillinux}/sbin/swapoff \"$used\" || true
-        fi
+    for label in ${toString devicesByLabel}; do
+        ${utillinux}/sbin/swapon -L \"$label\" || true
     done
+
+    # Remove swap devices not listed in swapDevices.
+    # !!! disabled because it doesn't work with labels
+    #for used in $(cat /proc/swaps | grep '^/' | sed 's/ .*//'); do
+    #    found=
+    #    for device in $ {toString swapDevices}; do
+    #        if test \"$used\" = \"$device\"; then found=1; fi
+    #    done
+    #    if test -z \"$found\"; then
+    #        ${utillinux}/sbin/swapoff \"$used\" || true
+    #    fi
+    #done
     
 end script
   ";