Linux Containers(LXC) allow running multiple isolated Linux instances (containers) on the same host. Containers share the same kernel with anything else that is running on it, but can be constrained to only use a defined amount of resources such as CPU, memory or I/O. A container is a way to isolate a group of processes from the others on a running Linux system.

1. Linux Containers

2. What's Linux Containers?
Linux Containers(LXC) allow running multiple isolated Linux instances
(containers) on the same host.
Containers share the same kernel with anything else that is running on it, but
can be constrained to only use a defined amount of resources such as CPU,
memory or I/O.
A container is a way to isolate a group of processes from the others on a
running Linux system.

3. Why Linux Containers?
 Provision in seconds / milliseconds
 Near bare metal runtime performance
 VM-like agility – it’s still “virtualization”
 Flexibility
• Containerize a “system”
• Containerize “application(s)”
 Lightweight
• Just enough Operating System (JeOS)
• Minimal per container penalty
Growing in popularity

4. Virtual Network Types
LXC containers support the following networking types:
• empty - creates only loopback interface and assigns it to the container.
• vlan - a vlan interface is linked with the interface specified in container's
configuration and is assigned to a the container.
• phys - an already existing interface is assigned to the container. This is useful
when you want to assign a physical network interface to a LXC container.
• none - will cause container to use host's network namespace.

5. Terminology in LXC
• Chroot :
A change root (chroot, or change root jail) is a section in the file system which
is isolated from the rest of the file system. For this purpose, the chroot command is used
to change the root of the file system.
• Cgroups :
Kernel Control Groups (commonly referred to as just “cgroups”) are a Kernel
feature that allows aggregating or partitioning tasks (processes) and all their children into
hierarchical organized groups to isolate resources.
• Container :
A “virtual machine” on the host server that can run any Linux system, for
example openSUSE, SUSE Linux Enterprise Desktop, or SUSE Linux Enterprise Server.

6. Terminology Continued...
• Container Name :
A name that refers to a container. The name is used by the lxc commands.
• Kernel Namespaces :
A Kernel feature to isolate some resources like network, users, and others for a
group of processes.
• LXC Host Server :
The system that contains the LXC system and provides the containers and
management control capabilities through cgroups.

7. Hypervisors vs. Linux
Containers
Hardware
Operating System
Hypervisor
Virtual Machine
Operating
System
Bins / libs
Ap
p
Ap
p
Virtual Machine
Operating
System
Bins / libs
Ap
p
Ap
p
Hardware
Hypervisor
Virtual Machine
Operating
System
Bins / libs
Ap
p
Ap
p
Virtual Machine
Operating
System
Bins / libs
Ap
p
Ap
p
Hardware
Operating System
Container
Bins / libs
Ap
p
Ap
p
Container
Bins / libs
Ap
p
Ap
p
Type 1 Hypervisor Type 2 Hypervisor Linux Containers
Containers are isolated,
but share OS and,
where appropriate, libs /
bins.

8. Docker vs. LXC vs. Hypervisor

9. Docker: LXC Virtualization?
Docker decouples the LXC provider from the operations
• LXC provider agnostic
Docker “images” run anywhere docker is supported
• Portability

10. Who’s Using LXC
Google app engine & infra is said to be using some form of LXC
RedHat OpenShift
dotCloud (now docker inc)
CloudFoundry (early versions)
Rackspace Cloud Databases
Parallels Virtuozzo (commercial product)

11. LXC Gaps
There are gaps…
•Lack of industry tooling / support
•Full orchestration across resources (compute / storage / networking)
•Fears of security
•Not a well known technology… yet
•Integration with existing virtualization and Cloud tooling
•Not much / any industry standards
•Missing skillset
•Slower upstream support due to kernel dev process

12. LXC: Use Cases For Traditional VMs
There are still use cases where traditional VMs are warranted.
•Virtualization of non Linux based OSs
•Windows
•AIX
•LXC not supported on host
•VM requires unique kernel setup which is not applicable to other VMs on
the host (i.e. per VM kernel config)

13. Features Of Linux Containers
Lightweight and resource – friendly
Comprehensive process and resource isolation
Run multiple versions of an operating system on a single server
Rapid and Easy deployment

14. Advantages
Easier maintenance and backup of individual virtual machines than one 'big'
linux server
Running different 'servers' on one physical computer saves hardware and
power costs
Security separation, hardware access from inside a vm may be restricted

15. Disadvantages
Speed issues if too many vm's are using the same hardware at the same time
(especially hard drive access, recommend a SSD).
If hardware breaks, all virtual machines machines are affected.
Might have problems accessing hardware, as access to that hardware might
be restricted.