Linux utils

Utils

Set date

sudo date --set "25 Sep 2013 15:00:00"

check disks on ubuntu

sudo lsblk

check that a node is pingable in bash

while ! ping -c1 bjjc_spec_22.ubuntu14 &>/dev/null; do :; done ;

how to tell if port 80 is listening?

telnet?

how do I know if the system trusts the certificate?

you use curl.

how to tell if port 80 is listening? What is listening on a particular port?

netstat -plnt

ubuntu vpn

https://hide.me/en/vpnsetup/ubuntu/openvpn/

Find large files

find / -xdev -type f -size +100M

see timestamps in history

echo 'export HISTTIMEFORMAT="%d/%m/%y %T "' >> ~/.bashrc ; source ~/.bashrc

• Generate large random file

dd if=/dev/urandom of=/var/log/mongodb/randomFile bs=1M count=200

• Add ssh key to a server

cat ~/.ssh/id_rsa.pub | ssh user@hostname 'cat >> .ssh/authorized_keys'

• Add identity to a server

ssh-copy-id -i ~.ssh/key_name.pub user@host

• Create a user

su - <username>
sudo visudo -f /etc/sudoers
sudo adduser --disabled-password <username>
(and there is deluser)
(I don't think I need this: usermod -aG sudo username ) - for making him a sudoer

• Establish a simple ssh port forward

10.0.0.x is public, 10.0.1.x is private. Do:

sudo sysctl net.ipv4.ip_forward=1
sudo iptables -t nat -A PREROUTING -p tcp -d 10.0.0.229 --dport 2270 -j DNAT --to-destination 10.0.1.224:22
sudo iptables -t nat -A POSTROUTING -j MASQUERADE

• Reset Chef UI Password

sudo -u opscode-pgsql  /opt/chef-server/embedded/bin/psql opscode_chef
update osc_users set hashed_password = '$2a$12$y31Wno2MKiGXS3FSgVg5UunKG48gJz0pRV//RMy1osDxVbrb0On4W' , salt ='$2a$12$y31Wno2MKiGXS3FSgVg5Uu' where username ='admin';

and login with user 'admin' and password 'password'.