Difference between revisions of "ArchWiki:Sandbox"

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 +
__NOTOC__
 +
[[Category:Sandbox]]
 +
''You can use this page to practise editing the wiki.''
  
[[Category:Virtualization]]
+
==Second heading==
[[Category:Kernel]]
+
This is a paragraph
[[de:Xen]]
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===Third heading===
[[es:Xen]]
+
This is a para also
[[ru:Xen]]
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====Fourth heading====
This document explains how to set up Xen 4.2 in Arch. It uses the new oxenstored / xl toolstack (replaces the xend / xm toolstack which was deprecated in Xen 4.1).
+
Me too<br>New line
  
==What is Xen?==
+
'''''bold and italics'''''
According to the Xen development team:
+
:"''The Xen hypervisor, the powerful open source industry standard for virtualization, offers a powerful, efficient, and secure feature set for virtualization of x86, x86_64, IA64, PowerPC, and other CPU architectures. It supports a wide range of guest operating systems including Windows®, Linux®, Solaris®, and various versions of the BSD operating systems.''"
+
  
The Xen hypervisor is a thin layer of software which emulates a computer architecture.  It is started by the boot loader of the computer it is installed on, and allows multiple operating systems to run simultaneously on top of it.  Once the Xen hypervisor is loaded, it starts the "Dom0" (short for "domain 0"), or privileged domain, which in our case runs a Linux kernel (other possible Dom0 operating systems are NetBSD and OpenSolaris). The physical hardware must, of course, be supported by this kernel to run Xen. Once the Dom0 has started, one or more "DomUs" (short for user domains, sometimes called VMs) can be started and controlled from Dom0.
+
''''' Bold and italics are in five apostrophes'''''
 +
=====Fifth Level Heading=====
 +
no indent
 +
:indent
 +
::more indent
 +
:::and more
  
Xen.org provides a [http://wiki.xen.org/wiki/Xen_Overview full overview]
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*bullet list
 +
*again
 +
**indent
 +
***more indent
 +
*bullet
 +
Link to pacman
 +
[[pacman]]
 +
'''Bold text'''''Italic text''[http://www.example.com link title]
  
==Types of Virtualization Available with Xen==
+
<s>strike out</s>
===Paravirtual (PV)===
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Paravirtualized guests require a kernel with support for Xen built in. This is default for all recent Linux kernels and some other Unix-like systems. Paravirtualized domUs usually run faster then HVM domains as they do not have to run in emulated hardware.
+
===Hardware Virtual (HVM)===
+
For OSes that do not natively support Xen (e.g. Windows), HVM offers full hardware virtualization. To use HVM in Xen, the host system hardware must include either Intel VT-x or AMD-V (SVM) virtualization support. In order to verify this, run the following command on the host system:
+
grep -E "(vmx|svm)" --color=always /proc/cpuinfo
+
If the above command does not produce output, then hardware virtualization support is unavailable and your hardware is unable to run Xen HVM guests. It is also possible that the host CPU supports one of these features, but that the functionality is disabled by default in the system BIOS. To verify this, access the host system's BIOS configuration menu during the boot process and look for an option related to virtualization support. If such an option exists and is disabled, then enable it, boot the system and repeat the above command.
+
  
== Obtaining Xen ==
+
{{Note|This is a note.}}
Xen is available from the AUR. The recommended current stable version is [https://aur.archlinux.org/packages.php?ID=14640 Xen 4.2], and the bleeding edge unstable package can be found [https://aur.archlinux.org/packages/xen-hg-unstable/ here.] Both packages provide the Xen hypervisor, current xl interface and all configuration and support files, including systemd services.  
+
  
Xen, unlike certain other virtualization systems, relies on a full install of the base operating system. Before attempting to install Xen, your host machine should have a fully operational and up-to-date install of Arch Linux. If you are building a new host from scratch, see the [[Installation_Guide|Installation Guide]] for instructions on installing Arch Linux.
+
{{Note|This is another note}}
  
Like all AUR packages, the Xen binaries are built from source. Note that it is possible (but not necessary) to build the package on a separate machine and transfer the xz package over, assuming that the machines share the same architecture (e.g. x86_64). For Xen, an internet connection is needed during its compilation because further source files are downloaded during the process. Xen.org recommends a host to be 64-bit. This requires the  'multilib' repository to be enabled in ''etc/pacman.conf''.
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{{Template:Sandbox|template-test}}
 
+
To build the package you will need the following:
+
 
+
base-devel zlib lzo2 python2 ncurses openssl libx11 yajl
+
libaio glib2 base-devel bridge-utils iproute gettext
+
dev86 bin86 iasl markdown git wget
+
+
optional packages:  ocaml ocaml-findlib
+
 
+
You will need to enable the 'extra' repository to get bin86. A tool such as [https://aur.archlinux.org/packages/yaourt/ yaourt] or [https://aur.archlinux.org/packages/packer/ packer] can aid in downloading, compiling and installing dependencies for AUR packages.
+
 
+
== Configuring Xen ==
+
The following configuration steps are required once the Xen package is installed.
+
 
+
'''The dom0 host requires'''
+
* an entry in the bootloader configuration file
+
* systemd services to be started at boot time
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* a xenfs filesystem mount point
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* bridged networking configuration
+
 
+
In addition to these required steps, the current xen.org wiki has a section regarding [http://wiki.xen.org/wiki/Xen_Best_Practices best practices for running Xen.] It includes information on allocating a fixed amount of memory dom0 and how to dedicate (pin) a CPU core for dom0 use.
+
 
+
=== Bootloader Configuration ===
+
Xen requires that you boot a special xen kernel (xen.gz) which in turn boots your system's normal kernel. A new bootloader entry is needed. To boot into the Xen system, we need a new menuentry in grub.cfg. The Xen package provides a grub2 generator file: ''/etc/grub.d/09_xen''. This file can be edited to customize the Xen boot commands, and will add a menuentry to your grub.cfg when the following command is run:
+
grub-mkconfig -o /boot/grub/grub.cfg
+
+
Example non-xen menuentry for LVM with gpt partition table
+
menuentry 'Arch ' {
+
  insmod part_gpt
+
  insmod lvm
+
  insmod ext2
+
  set root='lvm/vg0-arch'
+
  linux /boot/vmlinuz-linux root=/dev/mapper/vg0-arch ro init=/usr/lib/systemd/systemd quiet
+
  initrd /boot/initramfs-linux.img
+
}
+
 
+
The menuentry to boot the same arch system after Xen has been installed. Get the UUID for ''lvm/vg0-arch'' by using ''blkid''.
+
 
+
menuentry 'Arch Xen 4.2' {
+
  insmod lvm
+
  insmod part_gpt
+
  insmod ext2
+
  set root='lvm/vg0-arch'
+
  search --no-floppy --fs-uuid --set=root 346de8aa-6150-4d7b-a8c2-1c43f5929f99
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  multiboot /boot/xen.gz placeholder dom0_mem=1024M
+
  module /boot/vmlinuz-linux placeholder root=/dev/mapper/vg0-arch ro init=/usr/lib/systemd/systemd quiet
+
  module  /boot/initramfs-linux.img
+
}
+
 
+
Example for a physical partition
+
Arch Linux(XEN)
+
menuentry "Arch Linux(XEN)" {
+
    set root=(hd0,X)
+
  search --no-floppy --fs-uuid --set=root 346de8aa-6150-4d7b-a8c2-1c43f5929f99
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    multiboot /boot/xen.gz dom0_mem=1024M
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    module /boot/vmlinuz-linux-xen-dom0 root=/dev/sda ro
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    module /boot/initramfs-linux-xen-dom0.img
+
}
+
More at [https://wiki.archlinux.org/index.php/Grub2 Grub2]
+
 
+
=== Systemd Services ===
+
Issue the following commands as root so that the services are started at bootup:
+
# systemctl enable xenstored.service
+
# systemctl enable xenconsoled.service
+
# systemctl enable xendomains.service
+
 
+
=== Xenfs Mountpoint ===
+
Include in your ''/etc/fstab''
+
  none /proc/xen xenfs defaults 0 0
+
 
+
=== Bridged Networking ===
+
Previous versions of Xen provided a bridge connection whereas Xen 4.2 requires that network communications between the guest, the host (and beyond) is set up separately. The use of both DHCP and static addressing is possible, and the choice should be determined by your network topology. With basic bridged networking, a virtual switch is created in dom0 that every domu is attached to. More complex setups are possible, see the [http://wiki.xen.org/wiki/Xen_Networking Networking] article on the Xen wiki for details.
+
 
+
Netcfg greatly simplifies network configuration and is now included as standard in the ''base'' package. Example configuration files are provided in ''etc/network.d/examples'' and Xen 4.2 provides scripts for various networking configurations in ''/etc/xen/scripts''.
+
 
+
By default, Xen expects a bridge to exist named xenbr0. To set this up with netcfg, do the following:
+
 
+
# cd /etc/network.d
+
# cp examples/bridge xenbridge-dhcp
+
 
+
make the following changes to xen-bridge:
+
INTERFACE="xenbr0"
+
BRIDGE_INTERFACE="eth0" # Use the name of the external interface found with the 'ip link' command
+
DESCRIPTION="Xen bridge connection"
+
 
+
assuming your existing eth0 connection is called eth0-dhcp,
+
edit /etc/conf.d/netcfg
+
NETWORKS=(eth0-dhcp xenbridge-dhcp)
+
 
+
restart the network:
+
systemctl restart netcfg.service
+
 
+
when the prompt returns, check all is well
+
ip addr show
+
brctl show
+
+
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
+
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+
    inet 127.0.0.1/8 scope host lo
+
    inet6 ::1/128 scope host
+
      valid_lft forever preferred_lft forever
+
3: xenbr0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
+
    link/ether 00:1a:92:06:c0:c0 brd ff:ff:ff:ff:ff:ff
+
    inet 192.168.1.3/24 brd 192.168.1.255 scope global xenbr0
+
    inet6 fe80::21a:92ff:fe06:c0c0/64 scope link
+
      valid_lft forever preferred_lft forever
+
+
bridge name bridge id STP enabled interfaces
+
xenbr0 8000.001a9206c0c0 no eth0
+
 
+
=== Final Steps ===
+
Reboot your dom0 host and ensure that the Xen kernel boots correctly and that all settings survive a reboot. A properly set up dom0 should report show the following when you run xl list (as root):
+
# xl list
+
Name                                        ID  Mem VCPUs State Time(s)
+
Domain-0                                    0  511    2    r-----  41652.9
+
Of course, the Mem, VCPUs and Time columns will be different depending on machine configuration and uptime. The important thing is that dom0 is listed.
+
 
+
<<EDIT BREAK>>
+
 
+
 
+
== Using Xen ==
+
'''Each domU guest needs'''
+
* to be installed (refer to the distro's installation guide)
+
 
+
'''Each paravirtualized (pv) guests needs'''
+
* a mount point corresponding to the virtual disk (specified in its ''etc/fstab'' or equivalent)
+
* tty1 replaced by a virtual console (specified in its ''etc/inittab'' or equivalant, or systemd service file).
+
 
+
 
+
 
+
 
+
 
+
 
+
'''Reboot into your new Arch Dom0.'''
+
 
+
== Creating guest domains (domU) ==
+
+
=== Creating Paravirtualized (PV) Guests===
+
The general procedure is:
+
perform a normal or minimal installation of the distro that will become a guest; copy its kernel/initrd to a directory on the host; modify its /etc/fstab to use the virtual disk; modify its the way it sets up a terminal (getty); create a config file for xl.
+
 
+
== Running guest Domains ==
+
Start the guest domU and a console
+
# xl create /etc/xen/pv-squeeze.cfg
+
 
+
Check all is well:
+
# xl list
+
 
+
=== Useful xl command examples ===
+
# xl top
+
# xl list
+
# xl shutdown pv-squeeze
+
# xl destroy pv-squeeze
+
 
+
== Worked example for Debian Squeeze as a guest ==
+
Install Debian 6.0 (do not bother with graphical interface, install as little as possible). Having installed it, boot into in your new Arch Xen system and mount it.
+
 
+
The example has the guest Debian Squeeze installed onto /dev/vg0/pv_squeeze
+
 
+
# mkdir /tmp/squeeze
+
# mkdir -p /var/lib/xen/images/squeeze
+
# mount -text4 /dev/vg0/pv_squeeze /tmp/squeeze/
+
 
+
Copy the kernel and initrd to a location available Xen. n.b. Squeeze has softlinks (vmlinuz and initrd.img) in its root directory to the current kernel, so check you have copied a real kernel, and not just a link!
+
# cp /tmp/squeeze/vmlinuz /tmp/squeeze/initrd.img /var/lib/xen/images/squeeze
+
 
+
edit /tmp/squeeze/etc/fstab
+
change its root entry to begin with /dev/xvda1
+
# /dev/xvda1 / ext4 noatime,nodiratime,errors=remount-ro 0 1
+
 
+
Debian Squeeze uses ''/etc/inittab'' to configure its terminals. Other distros use other mechanisms. We need to replace the creation of terminals ''tty1'', ''tty2'' etc. with a single ''hvc0''.
+
 
+
Comment out any ''getty tty'' lines like these:
+
1:2345:respawn:/sbin/getty 38400 tty1
+
2:23:respawn:/sbin/getty 38400 tty2
+
+
Replace with the single line
+
hvc:2345:respawn:/sbin/getty 38400 hvc0
+
 
+
Create a guest configuration file by copying one of the given example files and editing as follows:
+
# cp /etc/xen/xlexample.pvlinux /etc/xen/pv-squeeze.cfg
+
 
+
edit /etc/xen/pv-squeeze.cfg with the following:
+
name = "squeeze.pvlinux"
+
kernel=/var/lib/xen/images/squeeze/vmlinuz
+
ramdisk=/var/lib/xen/images/squeeze/initrd.img
+
extra = "root=/dev/xvda1"
+
memory = 256
+
vcpus = 2
+
disk = [ '/dev/vg0/pv_squeeze,raw,xvda1,rw' ]
+
 
+
Start the guest domU and a console
+
# xl create /etc/xen/pv-squeeze.cfg
+
 
+
Check all is well:
+
# xl list
+
+
Name            ID  Mem VCPUs    State Time(s)
+
Domain-0        0  1024    2    r-----      26.2
+
squeeze.pvlinux  1    123    2    -b----      1.5
+
 
+
Start a console:
+
# xl console squeeze.pvlinux
+
+
( example output)
+
[
+
    0.000000] Initializing cgroup subsys cpuset
+
[    0.000000] Initializing cgroup subsys cpu
+
[    0.000000] Linux version 2.6.32-5-xen-amd64 (Debian 2.6.32-46) ...UTC 2012
+
[    0.000000] Command line: root=/dev/xvda1
+
[    0.000000] KERNEL supported cpus:
+
[    0.000000]  Intel GenuineIntel
+
[    0.000000]  AMD AuthenticAMD
+
[    0.000000]  Centaur CentaurHauls
+
...
+
 
+
== Installation notes for domU Paravirtualized guests ==
+
=== Arch ===
+
The default Arch initramfs images lack essential xen modules.
+
In the guest install, we need to add the following to mkinitcpio.conf
+
MODULES = "xen-blkfront xen-fbfront xen-netfront xen-kbdfront"
+
 
+
and then rebuild its initramfs-linux.img with ''mkinitcpio -p linux''.
+
 
+
=== Debian ===
+
Installation for Wheezy (testing) is identical to that for Squeeze (stable), see [[#Worked example for Debian Squeeze as a guest]].
+
 
+
== Common Errors ==
+
* 'xl list' complains about libxl
+
- Either you have not booted into the Xen system, or xen modules listed in ''xencommons'' script are not installed
+
 
+
* ''xl create'' fails
+
- check the guest's kernel is located correctly, check the pv-xxx.cfg file for spelling mistakes (like using ''initrd'' instead of ''ramdisk'')
+
 
+
* Arch linux guest hangs with a ctrl-d message
+
- press ctrl-d until you get back to a prompt, rebuild its initramfs described
+
 
+
* The domu guest hangs at 'crond'
+
- The guest's terminal needs to be set to ''hvc0'' instead of ''tty1'' See the Debian Squeeze example above.
+
 
+
* Error message "''failed to execute '/usr/lib/udev/socket:/org/xen/xend/udev_event' 'socket:/org/xen/xend/udev_event': No such file or directory''"
+
- caused by ''/etc/udev/rules.d/xend.rules''; xend is (a) deprecated and (b) not used, so it is safe to remove xend.rules
+
 
+
== Building and Installing Xen Hypervisor and Dom0 Host from Source ==
+
Xen recommends that a Xen host (dom0) is 64-bit, guests may be either 32-bit or 64-bit. To build such a system requires a mixed 64/32-bit installation and packages from the the Community repository; the host uses a network bridge and a modified entry in the bootloader configuration file (for example, grub.cfg). These notes assume an installation using systemd is in use, as is the default for a new installation of Arch. For these reasons, you may prefer to make a fresh installation of Arch on which to build and install Xen.
+
 
+
===Building Xen===
+
Building and installing Xen significantly modifies your system. Xen is an established program, but Xen 4.2 is extremely new. Consider Xen 4.2 on an Arch system to be untested. Consider yourself to be an alpha tester, perhaps make a throw-away Arch system for the Xen installation.
+
 
+
'''It is best practise to backup and highly recommended to make a fresh installation of Arch on which to build and install Xen.'''
+
 
+
* The build process installs additional source from git, so a working internet connection is required.
+
* systemd service files will be available soon. Until then we use (the currently still supported, but legacy) rc.d and rc.conf.
+
 
+
Edit /etc/pacman.conf to uncomment entries under repositries for multilib and community (three lines each).
+
Prepare for and perform a full system upgrade (pacman -Syu).
+
Install packages listed under 'Obtaining Xen'.
+
Download Xen Hypervisor 4.2 tarball from http://xen.org/products/downloads.html.
+
Unpack the tarball to a suitable location (tar xjf <path/to/tarball> location). Unfortunately, the build process also creates binaries and scripts for the old, deprecated ''xend/xm''.
+
The Xen documentation recommends building Xen as root.
+
 
+
# cd xen-4.2.0
+
# PYTHON=/usr/bin/python2
+
# export PYTHON
+
# ./configure
+
# make world
+
# make dist
+
 
+
The dist directory can be used to install Xen to any machine, but it
+
* sets the 'sticky' bit on all file permissions
+
* installs startup scripts to ''etc/init.d'' (equivalent of ''etc/rc.d'')
+
* includes some udev rules for 'xend' which creates LOTS of error messages when booting up (xend is not used, having been replaced by xendomains)
+
 
+
The only script we need from ''etc/init.d'' is ''xendomains'' since the systemd service files given below replace ''etc/init.d/xencommons''. The service files are based on those in Fedora 17 (which uses systemd and provides Xen 4.1). However, it places ''xendomains'' in ''/usr/libexec'' which is not present in Arch. The ''xendomain.service'' below uses ''/etc/xen/scripts'' as the location for ''xendomains''.
+
 
+
Fix these problems with
+
# cd dist
+
# chmod -R -s install/
+
# cp install/etc/init.d/xendomains install/etc/xen/scripts
+
# rm install/etc/init.d/*
+
# rmdir install/etc/init.d
+
# rm install/etc/udev/rules.d/xend.rules
+
 
+
If installing to another Arch system, make a tarball and copy it over:
+
# cd ..
+
# tar cjf ~/xen-dist-4.2.bz2 dist/
+
+
copy the tarball to the other installation, boot into it
+
use 'tar xjf xen-dist-4.2.bz2 .' to unpack
+
then install packages listed under 'Packages required for host'
+
+
Now change to the 'dist' directory and install
+
# cd dist
+
 
+
Whether installing now, or to another installation, from the ''dist'' directory issue:
+
# ./install.sh
+
 
+
=== Enabling Xen under Systemd ===
+
Add the following files
+
 
+
'''/etc/modules/load/xen.conf'''
+
xen-evtchn
+
xen-gntdev
+
xen-gntalloc
+
xen-blkback
+
xen-netback
+
xen-pciback
+
xen-acpi-processor
+
 
+
n.b The following were included in xencommons, but were not inserted by systemd
+
''evtchn'' ''gntdev'' ''netbk'' ''blkbk'' ''xen-scsibk'' ''usbbk'' ''pciback'' ''blktap2'' ''blktap''.
+
''xen-acpi-processor'' may not work on some machines. Remove this when getting error.
+
 
+
'''/usr/lib/systemd/system/xenstored.service'''
+
[Unit]
+
Description=Xenstored - daemon managing xenstore file system
+
Before=libvirtd.service libvirt-guests.service
+
After=dbus.service
+
RefuseManualStop=true
+
+
[Service]
+
Type=forking
+
PIDFile=/var/run/xenstored.pid
+
ExecStart=/usr/sbin/xenstored --pid-file /var/run/xenstored.pid $XENSTORED_ARGS
+
+
[Install]
+
WantedBy=multi-user.target
+
 
+
'''/usr/lib/systemd/system/xenconsoled.service'''
+
[Unit]
+
Description=Xenconsoled - handles logging from guest consoles and hypervisor
+
After=xenstored.service
+
+
[Service]
+
Type=simple
+
PIDFile=/var/run/xenconsoled.pid
+
ExecStart=/usr/sbin/xenconsoled
+
+
[Install]
+
WantedBy=multi-user.target
+
+
'''/usr/lib/systemd/system/xendomains.service'''
+
[Unit]
+
Description=Xendomains - start and stop guests on boot and shutdown
+
Requires=proc-xen.mount xenstored.service
+
After=proc-xen.mount xenstored.service xenconsoled.service
+
ConditionPathExists=/proc/xen
+
+
[Service]
+
Type=oneshot
+
RemainAfterExit=true
+
ExecStartPre=/usr/bin/grep -q control_d /proc/xen/capabilities
+
ExecStart=/etc/xen/scripts/xendomains start
+
ExecStop=/etc/xen/scripts/xendomains stop
+
+
[Install]
+
WantedBy=multi-user.target
+
 
+
'''/usr/lib/systemd/system/proc-xen.mount'''
+
  [Unit]
+
  Description=Mount /proc/xen files
+
  ConditionPathExists=/proc/xen
+
  RefuseManualStop=true
+
 
+
  [Mount]
+
  What=xenfs
+
  Where=/proc/xen
+
  Type=xenfs
+
 
+
Issue the following so that the services are started at bootup:
+
# systemctl enable xenstored.service
+
# systemctl enable xenconsoled.service
+
# systemctl enable xendomains.service
+
 
+
Add a new Xen menuentry in grub.cfg as described earlier and then '''reboot into the new Xen system''' and check all is well:
+
# xl list
+
+
Name                                        ID  Mem VCPUs State Time(s)
+
Domain-0                                    0  1024    2    r-----      6.1
+
 
+
n.b. ''xencommons'' sets the name "Domain-0" in the xenstored database. The current systemd service files do not do this, so at the moment ''xl list'' displays "(null)" as the name for Dom0.
+
 
+
==Resources==
+
* [http://www.xen.org/ The homepage at xen.org]
+
* [http://wiki.xen.org/wiki/Main_Page The wiki at xen.org ]
+

Revision as of 10:13, 25 June 2013

You can use this page to practise editing the wiki.

Second heading

This is a paragraph

Third heading

This is a para also

Fourth heading

Me too
New line

bold and italics

Bold and italics are in five apostrophes

Fifth Level Heading

no indent

indent
more indent
and more
  • bullet list
  • again
    • indent
      • more indent
  • bullet

Link to pacman pacman Bold textItalic textlink title

strike out

Note: This is a note.
Note: This is another note
template-test