arhcive: make it work when disk is attached before boot

This is a bit of a kludge (a lot of a kludge) but it will
get it running whilt I work on something better

THOUGHTS.txt

@@ -4412,3 +4412,154 @@ it can know what to update
 
 Maybe config.filesystem should specify /etc/s6-rc/compiled.new
 and something in early boot could symlink /etc/s6-rc/compiled to it
+
+Sat Mar 30 18:41:14 GMT 2024
+
+soft restart doesn't restart services that are invoked by trigger,
+because it has to do -p -u default so that it prunes services that
+were in the old config but not the new one. Ideally we need somehow
+to notify the trigger that it should respawn its service. Maybe
+we could add triggers to the force restart list, if there's a way
+to detect which they are?  don't want to do it by adding files in
+the service state directory if there may be oneshot triggers. Can
+there be oneshot triggers?
+
+The hashes file is built when we build the service database, so we
+could easily(?) add something in there to mark services that
+need poking whenever there's a restart. It's not perfect because the
+triggered services will be bounced unnecessarily, but remember that
+the alternative is a reboot ...
+
+Mon Apr  1 00:18:50 BST 2024
+
+i) I don't know if digressing into remote log shipping is a tangent or
+an important part of making services work well.
+
+ii) Should there be a single "machine state" value for all of the
+trigger services to reference, or is it better that each trigger
+service has its own private state, or (third option) one state
+per "state source"? We previously handwaved that a state source
+is a service
+
+services.addmember = services.udev.watch {
+  match = {
+    SUBSYSTEM = "net";
+    ID_PATH = "pci-0000:04:00.0";
+    ATTR.operstate = "up";
+  };
+
+  service = oneshot {
+    up = "ip link set dev $dev master $(output ${primary} ifname)";
+    down = "ip link set dev $(output ${member} ifname) nomaster";
+  };
+}
+
+
+Tue Apr  2 19:55:25 BST 2024
+
+We could do a test script for udev usb disk mounting, which uses the
+qemu monitor to add/remove a disk.
+
+
+./result/run.sh --flag -device --flag usb-ehci,id=xhci --flag -drive  --flag if=none,id=usbstick,format=raw,file=./stick.img
+
+(qemu) device_add  usb-storage,bus=xhci.0,drive=usbstick
+
+Fri Apr  5 17:11:46 BST 2024
+
+1) write a fennel thing that reads from the udev rebroadcast socket
+2) and can check sysfs for state
+3) set up mdevd in liminix
+
+
+Sat Apr  6 13:23:02 BST 2024
+
+I wonder if we could replace preinit with an execline script? One for
+the TODO stack
+
+
+Sun Apr  7 14:03:29 BST 2024
+
+1) we want to know what messages are sent from mdevd under various circumstances
+ - actually, right now the only relevant circumstances are updown and inout
+
+2) we might get a wider variety of messages from real hardware?
+
+3) if we log the raw messages, pref. with timestamps, then we can
+write tests for the parsing
+
+
+therefore: write a program that opens the netlink socket and logs
+all data received
+
+----
+
+what's the minimum we need here?  we need the inout test to open a
+uevent socket and use uevents to update some state that says whether the
+backup drive is plugged in
+
+rather awkwardly, uevents don't have filesystem labels. so we also need
+to run blkid to find the label of each partition, and ideally we do this
+while the partition is present, not each time we get an event for it.
+
+We have DEVNAME, DEVTYPE, SUBSYSTEM to indicate that a filesystem of interest
+may be present, we should use that as a trigger to scan any known
+
+
+
+add@/devices/pci0000:00/0000:00:13.0/usb1/1-1/1-1:1.0/host0/target0:0:0/0:0:0:0/block/sda/sda1
+ACTION=add
+DEVPATH=/devices/pci0000:00/0000:00:13.0/usb1/1-1/1-1:1.0/host0/target0:0:0/0:0:0:0/block/sda/sda1
+SUBSYSTEM=block
+MAJOR=8
+MINOR=1
+DEVNAME=sda1
+DEVTYPE=partition
+DISKSEQ=2
+PARTN=1
+SEQNUM=1528
+
+Some disks on loaclhost and noetbook have PARTNAME field - I assume
+this is because they're GPT disks. Would it actually be better to use this
+field than grovelling for filesystem label?
+
+Tue Apr  9 21:07:50 BST 2024
+
+Having waited for the appropriately labelled disk to appear, we then
+also have to communicate its path to the service that mounts it
+
+- create a symlink
+- or use an instanced service
+
+Creating a symlink will be fine if we can pass the symlink name as
+a param to fswait
+
+Wed Apr 10 20:53:48 BST 2024
+
+We think that fswait will evolve into a more general
+waiting-for-uevents tool. Maybe we could provide the matchers on the
+command line:
+
+waituevent -l /dev/volumes/backup-disk -s mount-srv devtype=partition partname=backup-disk
+
+Thu Apr 11 23:09:43 BST 2024
+
+lcommit d3a2e3a4cb80b631df2ab79d463c2c4d1adef37b
+commit 4a58cf9335116ce673fcf08f70f3bca921a4c9ad
+commit afca6d4b63dd39062f02827b3c29e16904770216
+
+Sun Apr 14 19:50:27 BST 2024
+
+how to get this on to main:
+ - make uevent-watcher package (it's fswait renamed)
+ - make mount service use it
+ - module for mdevd
+ - add nellie (generalise for other netlink uses w/params pid/family/groups)
+
+Mon Apr 15 19:59:43 BST 2024
+
+plan:
+
+introduce uevent-watcher command, update test to use it
+
+make mount service use it

devices/gl-mt300n-v2/default.nix

@@ -122,6 +122,7 @@
         # 20MB seems to give enough room to uncompress the kernel
         # without anything getting trodden on. 10MB was too small
         loadAddress = lim.parseInt "0x1400000";
+        appendDTB = true;
       };
 
       kernel = {

examples/arhcive.nix

@@ -28,34 +28,12 @@ in rec {
     ../modules/network
     ../modules/vlan
     ../modules/ssh
+    ../modules/usb.nix
     ../modules/watchdog
     ../modules/mount
   ];
   hostname = "arhcive";
 
-  kernel = {
-    config = {
-      USB = "y";
-      USB_EHCI_HCD = "y";
-      USB_EHCI_HCD_PLATFORM = "y";
-      USB_OHCI_HCD = "y";
-      USB_OHCI_HCD_PLATFORM = "y";
-      USB_SUPPORT = "y";
-      USB_COMMON = "y";
-      USB_STORAGE = "y";
-      USB_STORAGE_DEBUG = "n";
-      USB_UAS = "y";
-      USB_ANNOUNCE_NEW_DEVICES = "y";
-      SCSI = "y";
-      BLK_DEV_SD = "y";
-      USB_PRINTER = "y";
-      MSDOS_PARTITION = "y";
-      EFI_PARTITION = "y";
-      EXT4_FS = "y";
-      EXT4_USE_FOR_EXT2 = "y";
-      FS_ENCRYPTION = "y";
-    };
-  };
 
   services.dhcpc =
     let iface = config.hardware.networkInterfaces.lan;
@@ -105,11 +83,21 @@ in rec {
   };
 
   services.mount_external_disk = svc.mount.build {
-    device = "LABEL=backup-disk";
+    partlabel = "backup-disk";
     mountpoint = "/srv";
     fstype = "ext4";
   };
 
+  # until we support retained uevent state, we need to push coldplug
+  # events to mount_external_disk to account for the case that the
+  # disk is already plugged at boot time
+
+  services.fudge_coldplug = oneshot {
+    name = "fudge_coldplug";
+    up = "sleep 5; for i in /sys/class/block/*/uevent; do echo 'change' > $i ;done";
+    dependencies = [ services.mount_external_disk ];
+  };
+
   services.rsync =
     let
       secrets_file = oneshot rec {

modules/mount/default.nix

@@ -19,28 +19,36 @@ in {
       type = liminix.lib.types.serviceDefn;
     };
   };
-  config.system.service = {
-    mount = liminix.callService ./service.nix {
-      device = mkOption {
-        type = types.str;
-        example = "/dev/sda1";
-      };
-      mountpoint = mkOption {
-        type = types.str;
-        example = "/mnt/media";
-      };
-      options = mkOption {
-        type = types.listOf types.str;
-        default = [];
-        example = ["noatime" "ro" "sync"];
-      };
-      fstype = mkOption {
-        type = types.str;
-        default = "auto";
-        example = "vfat";
-      };
+  imports = [ ../mdevd.nix ];
+  config.system.service.mount =
+    let svc = liminix.callService ./service.nix {
+          partlabel = mkOption {
+            type = types.str;
+            example = "my-usb-stick";
+          };
+          mountpoint = mkOption {
+            type = types.str;
+            example = "/mnt/media";
+          };
+          options = mkOption {
+            type = types.listOf types.str;
+            default = [];
+            example = ["noatime" "ro" "sync"];
+          };
+          fstype = mkOption {
+            type = types.str;
+            default = "auto";
+            example = "vfat";
+          };
+        };
+    in svc // {
+      build = args:
+        let args' = args // {
+              dependencies = (args.dependencies or []) ++ [config.services.mdevd];
+            };
+        in svc.build args' ;
     };
-  };
+
   config.programs.busybox  = {
     applets = ["blkid" "findfs"];
     options = {

modules/mount/service.nix

@@ -1,10 +1,12 @@
 {
   liminix
+, uevent-watch
 , lib
 }:
-{ device, mountpoint, options, fstype }:
+{ partlabel, mountpoint, options, fstype }:
 let
   inherit (liminix.services) longrun oneshot;
+  device = "/dev/disk/by-partlabel/${partlabel}";
   options_string =
     if options == [] then "" else "-o ${lib.concatStringsSep "," options}";
   mount_service = oneshot {
@@ -18,14 +20,7 @@ in longrun {
   isTrigger = true;
   buildInputs = [ mount_service ];
 
-  # This accommodates bringing the service up when the device appears.
-  # It doesn't bring it down on unplug because unmount will probably
-  # fail anyway (so don't do that)
   run = ''
-    while ! findfs ${device}; do
-      echo waiting for device ${device}
-      sleep 1
-    done
-    s6-rc -b -u change ${mount_service.name}
+    ${uevent-watch}/bin/uevent-watch -s ${mount_service.name} -n ${device} partname=${partlabel} devtype=partition
   '';
 }

modules/watchdog/watchdog.nix

@@ -1,6 +1,7 @@
 {
   liminix
 , lib
+, s6
 }:
 { watched, headStart } :
 let
@@ -8,5 +9,5 @@ let
 in longrun {
   name = "watchdog";
   run =
-    "HEADSTART=${toString headStart} ${./gaspode.sh} ${lib.concatStringsSep " " (builtins.map (s: s.name) watched)}";
+    "PATH=${s6}/bin:$PATH HEADSTART=${toString headStart} ${./gaspode.sh} ${lib.concatStringsSep " " (builtins.map (s: s.name) watched)}";
 }

tests/inout/configuration.nix

@@ -47,20 +47,9 @@ in rec {
   rootfsType = "jffs2";
   hostname = "inout";
 
-  services.watch_mount_srv =
-    let
-      node = "/dev/disk/by-partlabel/backup-disk";
-      mount = oneshot {
-        name = "mount-srv";
-        up = "mount -t ext2 ${node} /srv";
-        down = "umount /srv";
-      };
-    in longrun {
-      name = "mount_srv";
-      run = ''
-        ${pkgs.uevent-watch}/bin/uevent-watch -s ${mount.name} -n ${node} partname=backup-disk devtype=partition
-      '';
-      dependencies = [ config.services.mdevd ];
-      buildInputs = [ mount ];
-    };
+  services.mount_backup_disk = svc.mount.build {
+    partlabel = "backup-disk";
+    mountpoint = "/srv";
+    fstype = "ext4";
+  };
 }