Difference between revisions of "Arch VServer"

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[[Category:Virtualization]]
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#REDIRECT [[Virtual Private Server]]
This article aims to provide all necessary information regarding the creation of a vserver host as well as vserver guests running Arch Linux. This will enable you to setup virtual servers that provide different services as if they were on different machines, with a very little overhead. You can get more information about virtual servers [http://en.wikipedia.org/wiki/Virtual_private_server here].
 
 
 
=Preparing the Host=
 
 
 
To prepare the vserver host environment, you will need to install both a vserver patched kernel, the vserver utilities and their dependencies which are located in the [[AUR]]. The required packages are {{AUR|dietlibc}}, {{AUR|beecrypt}}, {{AUR|kernel26-vserver}} (not found or {{AUR|linux-vserver}} orphan), and {{AUR|util-vserver}}
 
 
 
=Paths of Interest=
 
 
 
'''/etc/vservers''' : configuration root ( [http://www.nongnu.org/util-vserver/doc/conf/configuration.html ''reference''] )
 
: '''/etc/vservers/.defaults''' : configuration skeleton used when building new guests
 
:: '''/etc/vservers/.defaults/vdirbase''' : symlink to the folder containing vserver guests. This defaults to /vservers.
 
: '''/etc/vservers/<guest name>''' : guest specific configurations
 
 
 
=Preparing the Guests=
 
 
 
Vserver will launch guests from subfolders of ''/etc/vservers/.defaults/vdirbase''. As such, creating a new guest system is as simple as installing the required packages in a folder of the host. Furthermore, there's nothing stopping you ( and quite a few things encouraging you ) to mount filesystems to the subfolders of ''vdirbase'' and installing your guest in there.
 
 
 
If you plan on doing this often, I highly recommend that you write yourself a little batch script since most of these steps can be automated quite easily.
 
 
 
==Preparing the guest installation media==
 
 
 
'''NOTE''' : This is all heavily inspired from [[Install From Existing Linux]] and will therefore be quite brief when not mentioning Vserver specific steps.
 
 
 
===Optional: Base variables to follow along with the steps===
 
GuestName= # Name of the guest
 
GuestRoot=/etc/vservers/.defaults/vdirbase/$GuestName
 
GuestPackages= # Listing of packages to install via pacman
 
GuestDisk= # Installation target device
 
GuestNetDevice= # ex.: eth0, dummy0, etc...
 
GuestIP= # I think you get it
 
GuestContext= # Unique identifier for the guest, I go with the last part of the IP
 
 
 
===Optional: Preparing the guest disk===
 
# Create a LVM Physical Volume, a Volume Group and a Logical Volume ( [https://wiki.archlinux.org/index.php/Lvm#Create_Logical_Volumes wiki:LVM] )
 
# Create a filesystem on the lvm volume
 
# mkdir $GuestRoot
 
# mount /dev/$GuestDisk $GuestRoot
 
 
 
===Optional: Link the host and guest pacman cache===
 
# mkdir $GuestRoot/var/cache/pacman/pkg
 
# mount -o bind /var/cache/pacman/pkg $GuestRoot/var/cache/pacman/pkg
 
 
 
===Prepare Vserver===
 
# vserver $GuestName -m skeleton --context $GuestContext --interface $GuestNetDevice:$GuestIP --flags lock,virt_mem,virt_uptime,virt_cpu,virt_load,sched_hard,hide_netif --initstyle plain
 
# (optional) cd /etc/vservers/$GuestName/interfaces
 
# (optional) cp -r 0 1
 
# (optional) echo 'lo' > dev
 
# (optional) echo '127.0.0.$GuestContext' > ip
 
 
 
===Prepare the guest's filesystem===
 
# Prepare guest filesystem for the pacman db
 
## mkdir -p /newarch/var/lib/pacman
 
 
 
===Install the base system===
 
'''NOTE : ''' To save some time, it's probably a good idea to create a text file containing all the packages to install and call it via "pacman -S `cat $GuestPackages` -r $GuestRoot" instead of the following :
 
# pacman -S base -r $GuestRoot
 
# Optional: If you want to chroot into the newly created guest so as to install new packages, it might be a good idea to mount a few filesystems required by some packages.
 
## Bind /dev, /proc, /sys to the corresponding directories in $GuestRoot
 
# Modify guest configuration files to enable a smoother boot process
 
## Modify '''/etc/rc.shutdown''' by removing anything hardware/clock/mount related. This includes most everything under ''Saving Random Seed'.
 
## Modify '''/etc/rc.sysinit''' by anything hardware/clock/mount related.
 
## Modify '''/etc/syslog-ng.conf''' by removing file("/proc/kmsg")
 
 
 
=Troubleshooting=
 
==Viewing output from vserver $GuestName start / stop==
 
 
 
'''NOTE : ''' For me, this only worked in the actual consoles, not in X.
 
 
 
# Make sure that the device /dev/console exists in the guest
 
## If it does not, cp -a /dev/console $GuestRoot/dev/
 
 
 
==SSH will not start==
 
I noticed that /dev/null did not always get created properly in my first experimentations. Therefore I did a quick :
 
# cp -a /dev/null $GuestRoot/dev
 
# cp -a /dev/zero $GuestRoot/dev
 
 
 
Furthermore, if you're not using the dummy network driver and are attaching to the host's network interface, you'll want to configure the ListenAddress statement of /etc/ssh/sshd_config so that it binds only to the guest's IP address as opposed to 127.0.0.1.
 
 
 
==SSH immediately terminates the connection==
 
On my machine, SSH used to authenticate me correctly and log me in, but then immediately drop the connection without an explanation. Consulting /var/log/auth.log revealed the following:
 
 
 
sshd[17899]: pam_limits(sshd:session): Could not set limit for 'nice': Operation not permitted
 
 
 
This is easily fixed by commenting all '''nice''' related lines in /etc/security/limits.conf.
 
 
 
=Tips & Trick=
 
==Network via dummy adapters==
 
Here, you're either using the dummy module to create virtual network adapters or created interface aliases via /usr/sbin/ip. I went for the former and configured the host as such :
 
# ''/etc/sysctl.conf'' : net.ipv4.ip_forward=1<br>
 
Modify or add that statement to enable routing on the host
 
# ''/etc/rc.local''<br>
 
modprobe dummy numdummies=$NumberOfGuests<br>
 
ip link set dev dummy$GuestContext name $GuestName
 
 
 
This provides me with dummy interfaces that I can route / firewall that are all named the same as my guests... yay.
 
 
 
=More Resources=
 
[http://linux-vserver.org/Problematic_Programs Problematic Programs]<br>
 
[http://linux-vserver.org/Howto_make_bsd-style_init_sysv-compatible Make BSD style init SYSV compatible]<br>
 
[http://www.cedarcreeksoftware.com/an-even-easier-linux-vserver-tutorial.html Vserver tutorial]<br>
 
[http://linux-vserver.org/Installation_on_ArchLinux linux-vserver.org's Installation on ArchLinux]<br>
 
[http://wiki.linux-vserver.org/Networking_vserver_guests linux-verserver.org's networking tutorial]<br>
 
<!-- vim: set ft=Wikipedia: -->
 

Latest revision as of 02:15, 6 June 2015