scripts-and-fun

Useful stuff.

How to connect to UPB cluster

[email protected] ex: ssh [email protected]

If you want to make an instance for a virtual machine there is a tutorial here.

Then to access it: ssh -i ~/.ssh/openstack.key [email protected]

SCP command

download

scp student@host:host-file-10M.dat .

upload

scp blue-file-10M.dat student@host:\path\to\dir

Other ways to tranfer data

direct

server: opens TCP server that listens on port 12345, it stays open waiting for a client

nc -l 12345 > file-100M-nc.dat

client: make a client and connect to server

/usr/bin/time -v cat file-100M.dat | nc host 12345

Set connectivity between two stations

set ip address

ip address add 192.168.0.1/24 dev veth-red

activate interface

ip link set dev veth-red up

delete configurations:

ip address flush dev INTERFACE

check if config is okay with:

ip address show dev veth-red

ip link show dev veth-red

set default gateway

ip route add default via 10.10.10.1

check if config is okay with:

ip route show

activate routing on host

sysctl -w net.ipv4.ip_forward=1

NAT translation

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

Persistent configurations

For persistent configurations we write the commands in files. To activate de configs the interfaces need to be restarted:

ifdown INTERFACE

ifup INTERFACE

Firewall options using iptables

• telnet => port TCP 23
• SSH => port TCP 22
• FTP => port TCP 21

ex: iptables -A FORWARD -d green -p tcp --dport telnet -j REJECT # block telnet packets with destination = green

ex: iptables -A FORWARD -s red -j REJECT # block all traffic from red

ex: iptables -A FORWARD -d green -p tcp --dport ssh -j DROP # block ssh

ex: iptables -A FORWARD -d green -p tcp --dport ftp -j DROP # block ftp

ex: iptables -A FORWARD -s red -d green -p tcp --dport ssh -j ACCEPT # accept ssh traffic

option:

-A: append, adds at the end of table

-D: delete, deletes from table

-I: insert, inserts in table

choose table:

FORWARD the rules is applied on packets that will be routed

INPUT the rules is applied on packets that will be sent directly to system

OUTPUT the rules is applied on packets that leave the system

matching:

-d green: packets with destination = green

-s red: packets with source = red

-p tcp: TCP packets;

--dport telnet: destination port is telnet port (= 23, you can find it in /etc/services)

action:

-j REJECT: reject packet

-j ACCEPT: accept packet

-j DROP: drop packet

flush table

iptables -F FORWARD

check FORWARD table:

iptables -L FORWARD -v -n

SSH

All public key on a remote station are placed in ~/.ssh/authorized_keys

Generate ssh keys

ssh-keygen -t rsa

Copy .pub key on remote station

ssh-copy-id student@host

Command for corect permission on .ssh:

chmod 755 /home/ana/.ssh/

SSH config

~/.ssh/config

Host r

User student

HostName red