personal notes

personal_notes.sh

# change all occurances in git repository
git grep -l 'original_text' | xargs sed -i '' 's/original_text/new_text/g'

# For commenting multiple lines in vim:
:66,70s/^/#

# For uncommenting multiple lines in vim:
:66,70s/^#/

# What files changed for 1 commit in git repo
git whatchanged -1 --format=oneline

# About garbage collection
https://www.reddit.com/r/golang/comments/7tlw83/when_does_garbage_collection_occurs/

# Rust alternatives
- https://github.com/sharkdp/bat replacing cat
- https://github.com/sharkdp/fd replacing find
- https://github.com/sharkdp/hyperfine for benchmarking
- https://github.com/BurntSushi/ripgrep replacing grep
- https://github.com/ogham/exa replacing ls

# Ip tables debugging
https://backreference.org/2010/06/11/iptables-debugging/

# Setting alias and autocompletion and setting namespace for context in kubernetes
echo 'alias kc="kubectl"' >> ~/.bashrc && source ~/.bashrc && echo "source <(kubectl completion bash)" >> ~/.bashrc && complete -F __start_kubectl kc
kc config set-context $(kc config current-context) --namespace=default

# Experimenting with Net namespace
ip netns add red
ip netns add blue
ip link add veth-red type veth peer name veth-red-br
ip link add veth-blue type veth peer name veth-blue-br
ip link add v-net-0 type bridge
ip link set veth-red netns red
ip link set veth-blue netns blue
ip link set veth-red-br master v-net-0
ip link set veth-blue-br master v-net-0
ip -n blue link set lo up
ip -n red link set lo up
ip -n red link set veth-red up
ip -n blue link set veth-blue up
ip link set v-net-0 up# My host IP is 147.75.100.73
ip -n red addr add 147.75.100.1/24 dev veth-red
ip -n blue addr add 147.75.100.2/24 dev veth-blue
ip addr add 147.75.100.3/24 dev v-net-0# setup gateway
ip netns exec red ip route add default via 147.75.100.3
ip netns exec blue ip route add default via 147.75.100.3
# to ping outside world
echo 1 > /proc/sys/net/ipv4/ip_forward
iptables -t nat -A POSTROUTING -s 147.75.100.3/24 -j MASQUERADE
# Finally
ip netns exec blue ping 8.8.8.8

# Result of above experimentation:

If you want to extend your home L2 network, the bridge should not have an IP address
(it's just a bridge and does the forwarding based on Ethernet headers),
in that case you should configure the default gateway on the namespaces as it's configured
in your host (probably the IP address of the "box" that the ISP gives you). In this case the masquerading rule is not needed.
If you want to create a different subnet, they you should configure IP addresses for the veth interfaces
that don't overlap with your home network, the gateway on the namespaces would be an address in the host
and you'll need masquerading too.

Btw, having a different subnet is easier to configure.
Just the same you did but setting putting the veth in a non-overlapping network with your home network. 
If you want to extend the L2, IIRC you'd need to connect also the physical interface of your machine to
the bridge and if you still want the host to connect to the internet you'll have to create another veth pair,
one end connected to the bridge and the other end on the host (and assign an IP address to it).
It'll give host access to the internet.

# Dev hints
https://devhints.io/

# rerun the last command with sudo (and shout at your terminal while at it).
sudo !!