Category: Linux

Enable SSL on BitBucket Server

BitBucket Server alloow you to host git repositories. By default bitbucket server have url in following format

http://YOUR_IP_ADDR:7990/login

To install SSL, first point a domain to the server IP.

Install nginx

apt install nginx

Now install LetsEncrypt

wget https://raw.githubusercontent.com/serverok/server-setup/master/install/letsencrypt.sh
bash ./letsencrypt.sh

Get SSL in standalone mode. We use standalone mode because nginx will proxy all request to bitbucket server, so SSL validation will be difficult using nginx.

In this example, i will be using git.serverok.in, you need to replace with your actual domain.

systemctl stop nginx
certbot certonly --standalone -d git.serverok.in

Edit file

vi /usr/serverok/ssl-renew

Find

/usr/bin/certbot renew

Add before

systemctl stop nginx

Create file

vi /etc/nginx/sites-enabled/bitbucket.conf

Add

server {
    listen          443 ssl;
    server_name     git.serverok.in;
    ssl_certificate      	/etc/letsencrypt/live/git.serverok.in/fullchain.pem;
    ssl_certificate_key  	/etc/letsencrypt/live/git.serverok.in/privkey.pem;
    ssl_session_timeout  	5m;
    ssl_protocols  			TLSv1 TLSv1.1 TLSv1.2;
    ssl_ciphers  			HIGH:!aNULL:!MD5;
    ssl_prefer_server_ciphers   on;
    client_max_body_size 1000M;
    proxy_read_timeout 600s;

    location / {
        proxy_pass 			http://localhost:7990;
        proxy_set_header 	X-Forwarded-Host $host;
        proxy_set_header 	X-Forwarded-Server $host;
        proxy_set_header    X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header    X-Real-IP $remote_addr;
        proxy_redirect 		off;
    }
}

server {
    listen 80;
    server_name     git.serverok.in;
    return       301 https://git.serverok.in$request_uri;
}

Restart nginx server

systemctl restart nginx

Edit file

vi /var/atlassian/application-data/bitbucket/shared/bitbucket.properties

At end of the file, add following code

server.port=7990
server.secure=true
server.scheme=https
server.proxy-port=443
server.proxy-name=git.serverok.in

Now login to Bitbucket server, Go to Bitbucket Server administration area and click Server settings, and change Base URL to

https://git.serverok.in

Restart bitbucket server

systemctl stop atlbitbucket.service
systemctl start atlbitbucket.service

August 6, 2020

Configure KVM Bridge Network on Debian 10

Before you configure bridge network, make sure you have bridge-utils installed.

apt install bridge-utils

You may also need ifdown and resolvconf packages installed

apt install ifupdown resolvconf

Here is the default /etc/network/interfaces i had on the server

root@PAR-199235:~# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto enp1s0f0
allow-hotplug enp1s0f0
iface enp1s0f0 inet static
	address 163.172.107.119
	broadcast 163.172.107.255
	netmask 255.255.255.0
	gateway 163.172.107.1
	dns-nameservers 8.8.8.8

root@PAR-199235:~#

enp1s0f0 is name of the network interface card on the server.

To convert it to brudge configuration. You need to replace enp1s0f0 with br0.

Then add following to the file

    bridge_ports enp1s0f0
    bridge_stp off
    bridge_maxwait 5

Remember to replace enp1s0f0 with your actual network card interface name.

Also remove the line

allow-hotplug enp1s0f0

Here is the final /etc/network/interface file i have.

root@PAR-199235:~# cat /etc/network/interface
cat: /etc/network/interface: No such file or directory
root@PAR-199235:~# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface

auto br0
iface br0 inet static
	address 163.172.107.119
	broadcast 163.172.107.255
	netmask 255.255.255.0
	gateway 163.172.107.1
    bridge_ports enp1s0f0
    bridge_stp off
    bridge_maxwait 5
	dns-nameservers 8.8.8.8

root@PAR-199235:~#

August 4, 2020

bridge

Linux KVM Bridge network on Ubuntu
Configure KVM Bridge Network on Debian 10

August 4, 2020
ps
bash: ps: command not found

List process by memory usage
```
ps -eo vsz,pid,cmd | sort -nk 1
```
August 3, 2020
bash: ps: command not found
On a docker image, when i run ps, i get error
```
root@2efea503e8b7:~# ps
bash: ps: command not found
root@2efea503e8b7:~# 
```
To install ps on Debian/Ubuntu, run
```
apt -y install procps
```
August 3, 2020
Bash Script to Monitor Disk Usage
This script will check disk usage on / partition and email you if disk usage is above 80%

We can use df / command to find current disk usage
```
df /
```
As you can see, the result have 2 lines. We don’t need first line. To ignore first line, we can use
```
df / | grep -v 'Filesystem'
```
From the result, we only need the Use% part. In this case 66%, to find this, you can use awk command, that split the line, then prient specified part. In our case, we need 5th part.
```
df / | grep -v 'Filesystem' | awk '{print $5}'
```
To use disk usage % in our script for calculation, we need it converted to number. That is remove %. This can be done with sed command
```
df / | grep -v 'Filesystem' | awk '{print $5}' | sed 's/%//g'
```
Now we have disk usage as a number. We can use it in our script.
```
vi disk-usage-checker
```
Add following content to it
```
#!/bin/bash

CURRENT_USAGE=$(df / | grep -v 'Filesystem' | awk '{print $5}' | sed 's/%//g')
ALERT_ON=80

if [ "$CURRENT_USAGE" -gt "$ALERT_ON" ] ; then
    mail -s 'Disk Usage Warning' YOUR_EMAIL_HERE << EOF
Disk almost full on / partition. Current Useage: $CURRENT_USAGE%
EOF
fi
```
In above script, replace YOUR_EMAIL_HERE with your email address.

You can run the script daily using cronjob. If disk usage ever go above 80%, you will get email alert.

See bash
August 2, 2020
mutt

Read mails in Maildir folder

August 2, 2020
Read mails in Maildir folder
To read mail from Maildir folder, use mutt.

You can run
```
mutt -f /home/user/Maildir
```
To install mutt on Ubuntu/Debian, run
```
apt install mutt
```
August 2, 2020

Unblock an IP from fail2ban

To check if an IP is banned by fail2ban, run

zgrep "Ban" /var/log/fail2ban.log* | grep IP_ADDR_HERE

To unblock an IP, you should find the jail that caused the IP to be blocked.

In the following example, IP 152.67.19.86 is blocked by the sshd jail

2020-07-28 00:47:09,763 fail2ban.actions        [3494]: NOTICE  [sshd] Ban 152.67.19.86
2020-07-28 00:47:11,928 fail2ban.filter         [3494]: INFO    [sshd] Found 152.67.19.86 - 2020-07-28 00:47:11

To unban the IP, run

root@controlpanel:~# fail2ban-client set sshd unbanip 152.67.19.86
152.67.19.86
root@controlpanel:~#

You can see all jails with the command fail2ban-client status

root@controlpanel:/var/log# fail2ban-client status 
Status
|- Number of jail:	4
`- Jail list:	dovecot, postfix, pure-ftpd, sshd
root@controlpanel:/var/log#

See fail2ban

July 27, 2020

Install VirtualBox 6.1 on Ubuntu 18.04

First you need to add VirtualBox repository

sudo echo "deb [arch=amd64] https://download.virtualbox.org/virtualbox/debian bionic contrib" > /etc/apt/sources.list.d/virtualbox.list

Add Keys

wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
wget -q https://www.virtualbox.org/download/oracle_vbox.asc -O- | sudo apt-key add -

Do an apt upgrade

sudo apt-get update

If you have older version of VirtualBox installed, remove it

sudo apt remove virtualbox virtualbox-dkms virtualbox-qt

Install VirtualBox 6.1 with

sudo apt-get install virtualbox-6.1

If you use Vagrant, you may need to install latest version as the vagrant provided by ubuntu won’t work with VirtualBox 6.1

July 26, 2020

Install kvm on Debian 10
To install kvm on Debian 10, run
```
apt install -y qemu-kvm
```
Install libvirt, it is a tool to manage kvm
```
apt install libvirt-clients libvirt-daemon libvirt-daemon-system
```
Set libvirtd to start on boot
```
systemctl enable libvirtd
```
Restart libvirtd
```
systemctl restart libvirtd
```
You can see libvirtd status with
```
systemctl status libvirtd
```
Install virtinst, it is used to create virtual machine.
```
apt install virtinst
```
To see network, run
```
virsh net-list --all
```
Start the “default” network
```
virsh net-start default
```
Set default network to auto start on boot
```
virsh net-autostart default
```
Now you have kvm and libvirtd installed. You can create virtual machine using virtinst or Virt Manager

See KVM
July 25, 2020
chmod
chmod command allow you to change permission for a file or folder.
```
chmod 755 index.php
```
The above command changes the permission of file index.php to 755.
```
chmod -R 755 public_html
```
Above command change permisison of folder public_html and files inside it to 755. -R option is for recursively chmod.

Back to Linux Commands
July 24, 2020