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+NixOS Installation Stumbling Blocks
+###################################
+
+:date: 2017-09-04
+:tags: lessons,nixos
+:category: lessons
+:author: Jude N
+
+Here are some issues I ran into installing `NixOS`_ and how I eventually got around them.  
+
+
+Setting up a static IP since DHCP wasn't available.
+---------------------------------------------------
+My VM was hosted in an oVirt cluster where DHCP wasn't working/configured, so the installation CD booted without a network.  Here's how I manually configred a static IP:
+
+.. code-block:: bash
+
+   ifconfig enp0s3 <my-static-ip> netmask <my-netmask>
+   route add default gw <gateway-ip>
+   echo "nameserver 8.8.8.8" >> /etc/resolv.conf
+
+
+Partitioning the disk
+---------------------
+I spent a lot of time messing with various partitioning schemes until I stumbled across one that worked.  I didn't need disk encryption, and I didn't want to bother trying `UEFI with ovirt`_, so here's what I ended up with.
+
+- A 20G disk split into /dev/sda1 and /dev/sda2
+- /dev/sda1 is a 400MB 'WIN VFAT32' partition (type 'b', not type '4' !!)
+- /dev/sda2 is a LVM partition with the rest of the space
+- For the LVM, /dev/vg/swap is an 8G swap partition and /dev/vg/root has the rest of the LVM parition
+
+In retrospect, I think a lot of my partitioning pain may have been caused by trying to have /dev/sda1 set as a BIOS Parition (type '4'), since I suspect the BIOS partition has to be under 32M.
+
+Also in retrospect, I see only 23M is actually used on the current /boot parition, so maybe 400MB was way too much and I should have gone with /dev/sda1 being 32M and type '4'.  ¯\\_(ツ)_/¯
+
+I think I also ran into problems using fsck on the boot partition instead of fsck.vfat.
+
+When the boot partition wasn't working, grub would fall into rescue mode and the various 'set prefix / set root / insmod' fixes like `this one`_ or `this other one`_ didn't work.  
+
+What did work here was booting the system with the install CD again, mounting /mnt/boot manually and seeing that failed, or that /mnt/boot contained gibberish after mounting, and then unmounting /mnt/boot and using `testdisk`_ to fix the partition type.  Testdisk really saved the day.
+
+Mounting the boot partition
+---------------------------
+Before running nixos-install, I had to also mount the boot partition under /mnt/boot:
+
+.. code-block:: bash
+
+   > mount /dev/vg/root /mnt
+   > mkdir -p /mnt/boot
+   > mount /dev/sda1 /mnt/boot
+   > nixos-install
+
+
+Verify the /mnt/etc/nixos/hardware-configuration.nix device paths
+-----------------------------------------------------------------
+When I was messing with the disk partitioning, I rebuilt the /dev/sda1 partition a couple times.  Apparently when you do that, you get new UUID for the device.
+
+This meant the "/boot" file system in /mnt/etc/nixos/hardware-configuration.nix was using a device path that was no longer valid.  I updated the file to point to the current /boot device and reran 'nixos-install'.
+
+It looks like nixos-install isn't verifying the device paths are valid, since nixos-install ran OK with the invalid device paths.
+
+
+Configuring a static IP in /mnt/etc/nixos/configuration.nix
+-----------------------------------------------------------
+Here's what I ended up adding to the configuration.nix file to set up static IP:
+
+.. code-block:: bash
+
+   networking = {
+       hostName = '<my hostname>';
+       usePredictableInterfacenames = false;
+       interfaces.eth0.ip4 = [{
+           address= "<my ipv4 address>";
+           prefixLength = <my netmask prefix>;
+       }];
+       defaultGateway = "<my gateway>"
+       nameservers = [ "8.8.8.8" ];
+    };
+
+I also adding this boot setting:
+
+.. code-block:: bash
+
+    boot.load.grub.device = "/dev/sda";
+
+Sources
+-------
+- https://chris-martin.org/2015/installing-nixos (useful, but I didn't want UEFI or disk encryption - I got the 'have to mount /mnt/boot' step here)
+- https://gist.github.com/martijnvermaat/76f2e24d0239470dd71050358b4d5134
+- https://polycrystal.org/posts/2014-10-27-installing-nix.html
+
+.. _NixOS: https://nixos.org/
+.. _UEFI with ovirt: https://bugzilla.redhat.com/show_bug.cgi?id=1327846
+.. _this one: https://askubuntu.com/questions/119597/grub-rescue-error-unknown-filesystem
+.. _this other one: https://www.linux.com/learn/how-rescue-non-booting-grub-2-Linux
+.. _testdisk: http://www.cgsecurity.org/wiki/TestDisk