Merge 4e3b043 into 7f5cb19

doc/xen-setup.md

@@ -0,0 +1,205 @@
+# Setting up XEN for testing
+
+This document describes how to setup a XEN vm within a QEMU vm to test
+special XEN block devices (that are named like partitions but are in fact
+disks).
+
+For this document the XEN host (= QEMU guest) system uses Leap 15.0, the XEN guest uses SLE 15. But it
+whould work similar with other SUSE releases.
+
+## Preparing the QEMU host vm
+
+If you already have a Leap 15.0 vm, use it.
+
+Else create a new QEMU vm and install Leap 15.0, but:
+
+- add the Leap online repositories (the DVD image does not have XEN tools)
+- select `server` role
+- in the software selection, add the `XEN Virtualization Host and tools` pattern
+
+**Note**
+
+> It should be sufficient to add the `xen` and `xen-tools` packages to a standard Leap.
+
+Now reboot the QEMU vm and select `openSUSE Leap 15.0, with Xen hypervisor` at the boot menu.
+
+To communicate with the XEN vm you'll need a bridge device. Create a config like this
+
+```sh
+vm8101:/etc/sysconfig/network # cat ifcfg-br0
+STARTMODE='auto'
+BOOTPROTO='dhcp'
+BRIDGE='yes'
+BRIDGE_PORTS='eth0'
+```
+
+and run
+
+```sh
+wicked ifup br0
+```
+
+## Preparing the XEN guest
+
+> All the commands below are run inside the QEMU host vm.
+
+We'll need something to run inside the XEN vm. For this document SLE 15 is used (because it's comparatively small).
+
+Get `SLE-15-Installer-DVD-x86_64-GMC-DVD1.iso` and put it inside the QEMU vm, say as `/data/sle15.iso`
+
+```sh
+vm8101:/data # ls -l
+total 650240
+-rw-r--r-- 1 root root 665845760 Jul 19 14:25 sle15.iso
+```
+
+Mount it and extract kernel and initrd
+
+```sh
+vm8101:/data # mount -oloop,ro sle15.iso /mnt/
+vm8101:/data # cp /mnt/boot/x86_64/loader/{linux,initrd} .
+vm8101:/data # ls -l
+total 731160
+-r--r--r-- 1 root root  75971284 Jul 19 14:26 initrd
+-r--r--r-- 1 root root   6885728 Jul 19 14:26 linux
+-rw-r--r-- 1 root root 665845760 Jul 19 14:25 sle15.iso
+vm8101:/data # umount /mnt
+```
+
+You can use real devices or plain files to map into the XEN guest. For our example we'll try both.
+Let's get an empty file
+
+```sh
+vm8101:/data # dd if=/dev/zero of=disk1 bs=1G count=0 seek=60
+```
+
+The QEMU vm has a disk device for tests with two partitions
+
+```sh
+vm8101:~ # lsblk /dev/sdb
+NAME   MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
+sdb      8:16   0  60G  0 disk
+|-sdb1   8:17   0   6G  0 part
+`-sdb2   8:18   0   6G  0 part
+```
+
+A XEN guest vm is defined with a simple config file. For our guest it looks like
+
+```sh
+vm8101:/data # cat sle15.cfg
+name = "sle15"
+type = "pv"
+kernel = "/data/linux"
+ramdisk = "/data/initrd"
+cmdline = "startshell=1 sshd=1 password=xxxxx vnc=1 vncpassword=xxxxxxxx"
+memory = 512
+vif = [ '' ]
+disk = [ '/data/sle15.iso,,xvda,cdrom', '/dev/sdb2,,xvdb', '/data/disk1,,xvdc3' ]
+```
+
+This is a paravirtualized guest (full virtualization within another vm is a bit problematic) with
+our SLE 15 iso as CD-ROM and two disk devices. One maps `/dev/sdb2` as full disk device to `/dev/xvdb`.
+The other maps `/data/disk1` to `/dev/xvdc3`.
+
+Note that you are relatively free to name the device you map to (you don't have to start with `xvdc1`, for example).
+If the device name ends with a number the guest kernel will not try to read a partition table on the device.
+
+The `vif` line will create a network interface (`eth0`) for us.
+
+There are several options on how to interact with yast during the installation
+
+1. Run yast in ncurses mode. For this use
+  ```sh
+  cmdline = "startshell=1 sshd=1 password=xxxxx"
+  ```
+
+2. Run yast via VNC. For this use
+  ```sh
+  cmdline = "startshell=1 sshd=1 password=xxxxx vnc=1 vncpassword=xxxxxxxx"
+  ```
+  Note: the VNC password must be at leat 8 chars long.
+
+3. Run yast via SSH. For this use
+
+  ```sh
+  cmdline = "startshell=1 ssh=1 password=xxxxx"
+  ```
+
+## Starting the XEN guest
+
+Let's get going
+
+```sh
+xl create -c /data/sle15.cfg
+```
+
+With the config above this gets the installation system up and running and leaves you at a shell prompt
+
+```sh
+Starting SSH daemon... ok
+IP addresses:
+  10.0.2.18
+  fec0::216:3eff:fe58:3f40
+
+ATTENTION: Starting shell... (use 'exit' to proceed with installation)
+console:vm9650:/ #
+```
+
+There you can run yast (option 1. above) repeatedly in ncurses mode.
+
+With option 2. after running `yast`, connect to the VNC server. E.g.:
+
+```sh
+vncviewer 10.0.2.18:1
+```
+
+With option 3., connect to the XEN guest vm to run the installation
+
+```sh
+ssh -X 10.0.2.18
+```
+
+and run `yast` there.
+
+The disk layout of our XEN guest looks like this:
+
+```sh
+console:vm9650:/ # lsblk -e 7
+NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
+xvda    202:0    0   635M  1 disk
+|-xvda1 202:1    0   3.8M  1 part
+`-xvda2 202:2    0 630.9M  1 part /var/adm/mount
+xvdb    202:16   0     6G  0 disk
+xvdc3   202:35   0    60G  0 disk
+console:vm9650:/ # cat /sys/block/xvdb/range
+16
+console:vm9650:/ # cat /sys/block/xvdc3/range
+1
+```
+
+Note that `parted` works just fine with `/dev/xvdc3`.
+And if `/dev/xvdc3` happens to contain a partition table (here it does) you can run `kpartx` to access them
+
+```sh
+console:vm9650:/ # kpartx -a /dev/xvdc3
+console:vm9650:/ # lsblk -e 7
+NAME      MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
+xvda      202:0    0   635M  1 disk
+|-xvda1   202:1    0   3.8M  1 part
+`-xvda2   202:2    0 630.9M  1 part /var/adm/mount
+xvdb      202:16   0     6G  0 disk
+xvdc3     202:35   0    60G  0 disk
+|-xvdc3p1 254:0    0     6G  0 part
+`-xvdc3p2 254:1    0     6G  0 part
+```
+
+
+## Stopping the XEN guest
+
+Either do `halt -fp` within the XEN guest or `xl destroy sle15` on the XEN host.
+
+
+## Further reading
+
+If you want to extend the XEN configuration have a look at the man pages in the `xen-tools` package.
+For example `xl.cfg(5)` and `xl-disk-configuration(5)`.