Category: Linux

Install ShadowSocks server on Debian 10

To install ShadowSocks server on Debian 10, run

apt install -y shadowsocks

Create config file

vi /etc/shadowsocks/config.json

Add following

{
    "server":"SERVER_IP",
    "server_port":8044,
    "local_port":0,
    "password":"PASSWOARD_HERE",
    "timeout":600,
    "method":"aes-256-cfb"
}

You can change server_port if required.

To enable service, run

systemctl enable shadowsocks-server@config

To start shadowsocks proxy, run

systemctl start shadowsocks-server@config

For status/restart

systemctl status shadowsocks-server@config
systemctl restart shadowsocks-server@config

August 25, 2019

Install nslookup on ArchLinux
To install nslookup on ArchLinux, run
```
pacman -S dnsutils
```
August 20, 2019
Setting up MineCraft Server in Ubuntu
To setup MineCraft server on Ubuntu, first you need to install Java.
```
apt install openjdk-8-jre -y
```
Create a user to run minecraft
```
useradd -m --shell /bin/bash minecraft
```
You can set a password if you want direct SSH login to this user or login as root, then “su – minecraft”.
```
passwd minecraft
```
Login as user minecraft with SSH or “su”.

Download minecraft server .jar file from

https://www.minecraft.net/en-us/download/server/

At the time of writing, i downloaded
```
wget https://launcher.mojang.com/v1/objects/3dc3d84a581f14691199cf6831b71ed1296a9fdf/server.jar
```
Don’t use above link as it can get older, always go to minecraft site and get new link, so you get latest minecraft server jar file.

You can start minecraft server with command
```
java -Xmx1024M -Xms1024M -jar server.jar nogui
```
First time when you run, it exit with some error related to EULA.

You need to edit file
```
vi eula.txt
```
Set
```
eula=true
```
Now minecraft will run. You can create a run.sh file with following command for starting minecrat easily.
```
vi ~/start.sh
```
Paste following content
```
#!/bin/bash

java -Xmx1024M -Xms1024M -jar server.jar nogui
```
To make the file executable, chmod it 755
```
chmod 755 ~/start.sh
```
When you start minecraft from terminal/ssh, it get closed when you disconnect. To keep minecraft server running after you disconnect, use tmux or screen.
August 20, 2019
networking
On Ubuntu 19.04, networking service is provided by package ifupdown
```
apt install -y ifupdown
```
By default this package is not installed. So if you add network interface configuration in /etc/network/interfaces, it won’t work.

Ubuntu 18.04 + use netplan instead of ifupdown/networking service to configure network interfaces.

Linux KVM Bridge network on Ubuntu

Configure OVH Bridge Network from command line
August 18, 2019

Ubuntu Configure systemd-resolved

Latest Ubuntu/Debian use systemd-resolved for DNS resolution. On a fresh Ubuntu 19.04 install DNS failed to resolve.

root@ubuntu19:/# ping serverok.in
ping: serverok.in: Temporary failure in name resolution
root@ubuntu19:/#

To fix this, create file

mkdir /etc/systemd/resolved.conf.d/
vi /etc/systemd/resolved.conf.d/dns_servers.conf

Add content

[Resolve]
DNS=8.8.8.8 1.1.1.1

Restart systemd-resolved

systemctl restart systemd-resolved

You can find systemd-resolvd status with command

resolvectl status
systemd-resolve --status

To resolve a domain, use

resolvectl query serverok.in

August 18, 2019

Configure OVH Bridge Network from command line
If you have a Proxmox or VmWare ESXi server on OVH network, you need to configure network interface once virtual machine is created.

First login to OVH, go to IP page. Find the IP address you need to assign to this new VM, create a Virtual MAC. OVH allow 2 type of MAC. If you are using Proxmox, use OVH Mac. For VMWare ESXi, use vmware vmac.

Once you have Virual Mac. you need to configure it in your VM network interface settings. For Vmware ESXi

Now login to Virtial Machine, run following commands
```
ip link set NETWORK_INTERFACE_HERE up
ip addr add FO_IP_HERE dev NETWORK_INTERFACE_HERE
ip route add GW_IP_HERE dev NETWORK_INTERFACE_HERE
ip route add default via GW_IP_HERE dev NETWORK_INTERFACE_HERE
```
In above, replace

NETWORK_INTERFACE_HERE = name of your network interface. This can be found with command “ip link”. Normally it is eth0 or ensXXX.

FO_IP_HERE = this is the Failover IP you will be using for this Virtual Machine.

GW_IP_HERE = This is gateway IP. For OVH network, it will be your servers MAIN IP address with last number replaced with 254.

Here is an actial example.
```
ip link set ens192 up
ip addr add 178.33.35.183 dev ens192
ip route add 149.202.199.254 dev ens192
ip route add default via 149.202.199.254 dev ens192
```
This settings will be lost when you reboot OS. For configuring network interface permanantly, you can do
August 18, 2019

Install iperf3 on ArchLinux

To install iperf3 on ArchLinux, run

pacman -S iperf3

To do speed test

[root@tvmovies1 ~]# iperf3 -c ping.online.net -p 5209
Connecting to host ping.online.net, port 5209
[  5] local 163.172.50.206 port 50430 connected to 62.210.18.40 port 5209
[ ID] Interval           Transfer     Bitrate         Retr  Cwnd
[  5]   0.00-1.00   sec   282 MBytes  2.36 Gbits/sec    0    720 KBytes       
[  5]   1.00-2.00   sec   280 MBytes  2.35 Gbits/sec    0    755 KBytes       
[  5]   2.00-3.00   sec   281 MBytes  2.36 Gbits/sec   11    755 KBytes       
[  5]   3.00-4.00   sec   280 MBytes  2.35 Gbits/sec    0    758 KBytes       
[  5]   4.00-5.00   sec   281 MBytes  2.36 Gbits/sec    0    758 KBytes       
[  5]   5.00-6.00   sec   256 MBytes  2.15 Gbits/sec  1507   42.4 KBytes       
[  5]   6.00-7.00   sec   115 MBytes   965 Mbits/sec  6917    130 KBytes       
[  5]   7.00-8.00   sec   114 MBytes   954 Mbits/sec  6643   48.1 KBytes       
[  5]   8.00-9.00   sec   114 MBytes   954 Mbits/sec  6749    119 KBytes       
[  5]   9.00-10.00  sec   112 MBytes   944 Mbits/sec  6923   38.2 KBytes       
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval           Transfer     Bitrate         Retr
[  5]   0.00-10.00  sec  2.07 GBytes  1.77 Gbits/sec  28750             sender
[  5]   0.00-10.00  sec  2.06 GBytes  1.77 Gbits/sec                  receiver

iperf Done.
[root@tvmovies1 ~]#

Here we do speed test with http://ping.online.net, they run iperf3 server on port 5209

August 17, 2019

Install netdata on ArchLinux
First update the packages with
```
pacman -Syu
```
Install netdata
```
pacman -S netdata
```
Enable and start netdata
```
systemctl enable netdata
systemctl start netdata
```
August 17, 2019
Ubuntu remove SSH welcome message
When you login to an Ubuntu server using SSH, you get welcome message like

On most Linux systems, this is generated by /etc/motd. On Ubuntu, MOTD (message of the day) generated dynamically with some scripts. I don’t want to see all the marketing message from Ubuntu everyday.

To disable MOTD on Ubuntu, just delete the scripts from /etc/update-motd.d/
```
rm -f /etc/update-motd.d/*
```
If you want a differnt motd, you can put a shell script in this folder.

Method 2

Another way to disable motd is by disabling pam_motd.so module.

Edit files
```
/etc/pam.d/login
/etc/pam.d/sshd
```
Comment out the lines related to pam_motd.so
```
session    optional     pam_motd.so  motd=/run/motd.dynamic
session    optional     pam_motd.so noupdate
```
August 17, 2019
nmtui
nmtui allow you to configure network interface if you are using network manager.

On Debian/Ubuntu, it is part of network-manager package
```
apt install network-manager
```
August 16, 2019

Install Linux Kernel 5.0 on Ubuntu 18.04 LTS

Ubuntu 18.04 was released with Linux kernel 4.15

root@DUS-147022:~# hostnamectl
   Static hostname: DUS-147022.op-net.com
         Icon name: computer-desktop
           Chassis: desktop
        Machine ID: 1fcb383ac03e4299a3b994dca4c51a10
           Boot ID: 66d616e9b11145c38387d71f9c48a4bd
  Operating System: Ubuntu 18.04.3 LTS
            Kernel: Linux 4.15.0-58-generic
      Architecture: x86-64
root@DUS-147022:~#

On 8 Aug 2019, Cannonical released Ubuntu 18.04.3 LTS with Linux Kernel 5.0.

If you are using older Ubuntu 18.04 point release, you won’t get newer kernel when you do software upgrade.

To get newer Linux kernal installed, you need to install Hardware enablement (HWE) stack, this provide newer kernel that provide support for latest hardware.

To install Hardware enablement (HWE) stack, run

apt install linux-generic-hwe-18.04

if this is Desktop computer, you may need to run

apt install linux-generic-hwe-18.04 xserver-xorg-hwe-18.04

after installing, reboot

reboot

after reboot, you will see latest Linux Kernel.

boby@sok-01:~$ hostnamectl
   Static hostname: sok-01
         Icon name: computer-desktop
           Chassis: desktop
        Machine ID: 70486772aac1410c9a8031851ab60a0d
           Boot ID: 6c946c08f95d4c6b883e6790ab83e728
  Operating System: Ubuntu 18.04.3 LTS
            Kernel: Linux 5.0.0-25-generic
      Architecture: x86-64
boby@sok-01:~$

August 16, 2019

ping: unknown host localhost

On a server, ping localhost did not work

root@cloud1:~# ping localhost
ping: unknown host localhost
root@cloud1:~#

/etc/hosts files was proper, had entry for localhost.

root@cloud1:~# cat /etc/hosts | grep localhost
127.0.0.1 localhost
::1 ip6-localhost ip6-loopback
root@cloud1:~#

problem was due to /etc/nsswitch.conf file missing in the server. To fix create file

vi /etc/nsswitch.conf

Add

# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd:         compat systemd
group:          compat systemd
shadow:         compat
gshadow:        files

hosts:          files mdns4_minimal [NOTFOUND=return] dns myhostname
networks:       files

protocols:      db files
services:       db files
ethers:         db files
rpc:            db files

netgroup:       nis

Set permission for the file

chmod 644 /etc/nsswitch.conf

August 10, 2019

Category: Linux

Method 2