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 here.
- 1 Preparing the Host
- 2 Paths of Interest
- 3 Preparing the Guests
- 4 Troubleshooting
- 5 Tips & Trick
- 6 More Resources
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, AUR, AUR (not found or AUR orphan), and AUR
Paths of Interest
/etc/vservers : configuration root ( 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 ( 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
- 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")
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 $GuestRoot/dev
Furthermore, if you're not using the dummy network driver and are attaching to the host's network interface, you'll want to configure the ListenAddress statement of /etc/ssh/sshd_config so that it binds only to the guest's IP address as opposed to 127.0.0.1.
SSH immediately terminates the connection
On my machine, SSH used to authenticate me correctly and log me in, but then immediately drop the connection without an explanation. Consulting /var/log/auth.log revealed the following:
sshd: pam_limits(sshd:session): Could not set limit for 'nice': Operation not permitted
This is easily fixed by commenting all nice related lines in /etc/security/limits.conf.
Tips & Trick
Network via dummy adapters
Here, you're either using the dummy module to create virtual network adapters or created interface aliases via /usr/sbin/ip. I went for the former and configured the host as such :
- /etc/sysctl.d/99-sysctl.conf : net.ipv4.ip_forward=1
Modify or add that statement to enable routing on the host
modprobe dummy numdummies=$NumberOfGuests
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.