LXC Alpinelinux Simple

DRAFT

Linux Containers (LXC) provides containers similar to BSD Jails, Linux VServers and Solaris Zones. It gives the impression of virtualization, but shares the kernel and resources with the "host".

Setup walkthrough

Basic setup that gets you going, you would still need to read main LXC documentations for advanced features.

Objective

1. Install Alpinelinux.
2. Install LXC and its dependencies.
3. Download required files.
4. Start a LXC instance.
5. Test basic networking.

Test bed

WIP

• Describe here the test bed/setup used to run the scripts below.

1. MODEL: Dell Laptop.
2. CPUs
   1. CPU: Intel i5 2nd generation.
   2. CPU: Intel i5 3rd generation with virtualization enabled (2nd setup).
3. RAM: 8GB

Install Alpinelinux

1. Diskless installs (Ram based)
2. SYS installs

Tip: - for further setup to work correctly, its assumed that alpinelinux installed in done for version between v3.21.x and v3.22.x

Install LXC and its dependencies

v3.21.x-v3.22.x

Install the required packages (as root):

apk add lxc lxcfs lxc-templates-legacy-alpine bridge

Setup LXC

-v3.22.x

Get/set required files (as root):

cd ~ wget https://dl-cdn.alpinelinux.org/v3.21/releases/x86_64/alpine-minirootfs-3.21.1-x86_64.tar.gz cd /var/lib/lxc/ mkdir -p guest1/rootfs cd guest1/rootfs tar -zxf ~/alpine-minirootfs-3.21.1-x86_64.tar.gz apk add --root ./ alpine-base

v3.21.x-v3.22.x

Fix some issues (as root),

#### Minor/manual changes #### rm -f /var/lib/lxc/guest1/rootfs/dev/null rm -f /var/lib/lxc/guest1/rootfs/dev/zero

v3.21.x-v3.22.x

Content of /etc/lxc/bridgenat.conf. (Not needed for manual setup)

lxc.net.0.type = veth
lxc.net.0.flags = up
lxc.net.0.link = br0
lxc.net.0.name = eth1
lxc.net.0.ipv4.address = 192.168.10.2/24 192.168.1.255
lxc.net.0.ipv4.gateway = 192.168.10.1
lxc.net.0.veth.pair = veth-if-10

v3.21.x-v3.22.x

Content of guest1/config (need to create once)

# default config file that was generated using
# 'lxc-create -n alpine -f /etc/lxc/bridgenat.conf -t alpine'
# config below was modified to a simpler manual setup

lxc.net.0.type = veth
lxc.net.0.flags = up
lxc.net.0.link = br0
lxc.net.0.name = eth1
  
lxc.net.0.ipv4.address = 192.168.10.10/24 192.168.10.255
lxc.net.0.ipv4.gateway = 192.168.10.1
  
# needs to be uniq per guest
lxc.net.0.veth.pair = veth-if-10
  
lxc.rootfs.path = dir:/var/lib/lxc/guest1/rootfs
  
# Specify container architecture.
lxc.arch = x86_64
  
# Set hostname.
lxc.uts.name = guest1
  
# If something doesn't work, try to comment this out.
lxc.cap.drop = sys_admin
  
# Comment this out if you have to debug processes by tracing.
lxc.cap.drop = sys_ptrace
  
# Comment this out if required by your applications.
lxc.cap.drop = setpcap
  
# Include common configuration.
lxc.include = /usr/share/lxc/config/alpine.common.conf

Start a LXC instance

v3.21.x-v3.22.x

Start these net/services as root

# brctl addbr br0 # need to set this first once

# ln -s lxc /etc/init.d/lxc.guest1 # need to do once

# rc-service lxc.guest1 start

# KNOWN ISSUEs:
   # * /var/lib/lxc/guest1/rootfs is on tmpfs and ALLOW_TMPFS is not set
   # * ERROR: lxc.guest1 failed to start

# To avoid seeing error like above in DISKLESS installs,
# SOLUTION is: move /var/lib/lxc to disk, then create a symlink of lxc

Use LXC

v3.21.x-v3.22.x

Start these net/services as root

# lxc-attach -n guest1 passwd root # add a passwd exit lxc-console -n guest1 # this works !!!, need to create user first then su -l to root # OR use lxc-attach to change passwd of root

Fix some basic networking

v3.21.x-v3.22.x

WIP

Step 1. Bring br0 up (on HOST)

# ifconfig br0 192.168.10.1 netmask 255.255.255.0 up

# brctl show
bridge name	bridge id		STP enabled	interfaces
br0		8000.febdf6e3a9f2	no		veth-if-10

# ifconfig br0
br0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.10.1  netmask 255.255.255.0  broadcast 192.168.10.255
...

Step 2. Bring eth1 up (on GUEST)

• Nothing to be done.

guest1:/tmp# ifconfig 
eth1      Link encap:Ethernet  HWaddr 5E:2A:70:E0:D9:49  
          inet addr:192.168.10.10  Bcast:192.168.10.255  Mask:255.255.255.0
...

Test networking

v3.21.x-v3.22.x

Step 1. Test on HOST - IMPORTANT: remove firewall if any

$ nc -l 1234 > /tmp/filename.out

Step 2. Test on GUEST

# echo -e "aaa\nbbb" > test.txt

# nc 192.168.10.1 1234 < test.txt

Step 3. Test on HOST

$ cat /tmp/filename.out

See also

• Qemu-simple

Resources

1. https://linuxcontainers.org/lxc/manpages/
2. https://manned.org/pkg/alpine-3.22/lxc-doc