2018 Top 10的Snap 套件

即將邁入2019，回顧一下2018 前10名最受喜愛的snap套件是哪些呢？

剛看了一下敝公司的官方網頁，以下有Top10的排行榜唷～ :D
https://blog.ubuntu.com/2018/12/27/top-snaps-in-2018

不過說真的，我個人蠻常用的Skype, mailspring, simplenote現在都用snap來安裝，並且會自動定時更新，超方便的呀～

不知道何時會有line for snap?

How can I setup an IPv6 router via radvd on Ubuntu 18.04 LTS?

What's radvd?
Router advertisement daemon.

Reference:
https://zh.wikipedia.org/wiki/Radvd
http://www.litech.org/radvd/

一般來說 IPv6 Client決定Global IPv6的方式有兩種，分別是Stateless與Stateful，預設radvd是採用stateless IPv6，不過透過更改某個參數(M flag)，就可以轉換成stateful，但是此時網路上必須有對應的DHCPv6 server來負責管理與分配IPv6 address。

網路上可以找到很多先進寫的資料關於Stateless與Stateful的差異，我也就不班門弄斧了，廢話不多說，直接進入主題，如何架設radvd在Canonical/Ubuntu 18.04 LTS。

Steps:

Step1. Install radvd package.

$ sudo apt-get install radvd

Step2. Copy example file of radvid.conf from /usr/share/doc/radvd/examples/ to /etc.

$ sudo cp /usr/share/doc/radvd/examples/radvd.conf.example /etc/radvd.conf

Step3. Open/Edit radvd.conf

根據你的需求，去配置相關的參數，最重要的應該是prefix，更多詳細的參數可以參考man page。

https://www.systutorials.com/docs/linux/man/5-radvd.conf/

Step4. Restart radvd

$ sudo systemctl restart radvd; sudo systemctl enable radvd

以上一個簡單的IPv6 stateless的Router已經架設完成，IPv6 client現在自己可以搭配prefix自動產生host ID。

How can I configure Ubuntu 16 to start teamviewer automatically?

Steps:

1. Opened /etc/init.d/rc.local

$ sudo vi /etc/init.d/rc.local

2. Added teamviewer's command and parameter below in file rc.local:

teamviewer passwd ubuntu

3. Restart system

4. Examine if teamviewer daemon can work as expected:

$ systemctl status teamviewerd
● teamviewerd.service - TeamViewer remote control daemon
   Loaded: loaded (/etc/systemd/system/teamviewerd.service; enabled; vendor preset: enabled)
   Active: active (running) since 三 2018-08-15 11:00:14 CST; 1min 25s ago
  Process: 1555 ExecStart=/opt/teamviewer/tv_bin/teamviewerd -d (code=exited, status=0/SUCCESS)
 Main PID: 1567 (teamviewerd)
   CGroup: /system.slice/teamviewerd.service
           └─1567 /opt/teamviewer/tv_bin/teamviewerd -d

$ ps aux | grep -i teamviewer
root      1567  0.3  0.3 1181612 12212 ?       Sl   11:00   0:00 /opt/teamviewer/tv_bin/teamviewerd -d
u         1890  0.3  2.2 1990224 88556 ?       Sl   11:00   0:00 /opt/teamviewer/tv_bin/TeamViewer

Afterwards, you can remote control host via Partner ID and password which is ubuntu in this example.

How can I create a multiboot USB stick from Linux?

You can refer to https://www.pendrivelinux.com/multiboot-create-a-multiboot-usb-from-linux/

It works for me!

Above you can see that I am able to boot Ubuntu 16.03 as well as 18.04 with one USB stick w/o problem.

But somehow you've to disable security boot in BIOS.

Enjoy~

How can I setup a proxy server in Ubuntu 16.04?

Step1. Install package squid

# sudo apt-get install -y squid

Step2. To setup common proxy settings:

# sudo vi /etc/squid/squid.conf

To add some lines below:

# line 977

acl lan src 192.168.1.0/24

(where 192.168.1.0 means network you would like to allow client to access your proxy server)

# line 1189

http_access allow lan

(Allow lan here)

# line 1602

http_port 3128

(To modify default proxy port if needed)

Step3. Restart squid

# sudo systemctl restart squid

Step4. Examine squid service

# sudo systemctl status squid

● squid.service - LSB: Squid HTTP Proxy version 3.x

Loaded: loaded (/etc/init.d/squid; bad; vendor preset: enabled)

Active: active (running) since 四 2018-04-26 15:24:04 CST; 1min 56s ago

Docs: man:systemd-sysv-generator(8)

Process: 3088 ExecStop=/etc/init.d/squid stop (code=exited, status=0/SUCCESS)

Process: 3119 ExecStart=/etc/init.d/squid start (code=exited, status=0/SUCCESS)

CGroup: /system.slice/squid.service

├─3159 /usr/sbin/squid -YC -f /etc/squid/squid.conf

├─3161 (squid-1) -YC -f /etc/squid/squid.conf

├─3162 (logfile-daemon) /var/log/squid/access.log

└─3163 (pinger)

四 26 15:24:04 uc16-VirtualBox systemd[1]: Starting LSB: Squid HTTP Proxy version 3.x...

四 26 15:24:04 uc16-VirtualBox squid[3119]: * Starting Squid HTTP Proxy squid

四 26 15:24:04 uc16-VirtualBox squid[3159]: Squid Parent: will start 1 kids

四 26 15:24:04 uc16-VirtualBox squid[3119]: ...done.

四 26 15:24:04 uc16-VirtualBox systemd[1]: Started LSB: Squid HTTP Proxy version 3.x.

四 26 15:24:04 uc16-VirtualBox squid[3159]: Squid Parent: (squid-1) process 3161 started

# netstat -tupln | grep 3128

tcp6 0 0 :::3128 :::* LISTEN 3161/(squid-1)

Done ~

In proxy client side:

You can use tcpdump or wireshark to ensure that http request will go to proxy server after you configured http proxy server within browser.

root@server1:~$ sudo tcpdump -n -v -i any port 3128

tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size 262144 bytes

15:29:06.382845 IP (tos 0x0, ttl 64, id 2257, offset 0, flags [DF], proto TCP (6), length 145)

192.168.1.211.40994 > 192.168.1.254.3128: Flags [P.], cksum 0x85a5 (incorrect -> 0x9ba8), seq 670754847:670754940, ack 314235908, win 237, options [nop,nop,TS val 1731217504 ecr 1884649606], length 93

15:29:06.383195 IP (tos 0x0, ttl 64, id 35299, offset 0, flags [DF], proto TCP (6), length 212)

192.168.1.254.3128 > 192.168.1.211.40998: Flags [P.], cksum 0xbf6c (correct), seq 2355697405:2355697565, ack 1986317666, win 486, options [nop,nop,TS val 1884649610 ecr 1731217476], length 160

15:29:06.383264 IP (tos 0x0, ttl 64, id 17423, offset 0, flags [DF], proto TCP (6), length 52)

192.168.1.254.3128 > 192.168.1.211.40994: Flags [.], cksum 0xaba6 (correct), ack 93, win 503, options [nop,nop,TS val 1884649610 ecr 1731217501], length 0

15:29:06.383359 IP (tos 0x0, ttl 64, id 2258, offset 0, flags [DF], proto TCP (6), length 1353)

192.168.1.211.40994 > 192.168.1.254.3128: Flags [P.], cksum 0x8a5d (incorrect -> 0x8fe0), seq 93:1394, ack 1, win 237, options [nop,nop,TS val 1731217505 ecr 1884649610], length 1301

15:29:06.384198 IP (tos 0x0, ttl 64, id 9911, offset 0, flags [DF], proto TCP (6), length 268)

How can I setup a Linux NAT Router in Ubuntu?

Steps:

1. Enable packet forwarding for IPv4 between NICs:

• Open and edit /etc/sysctl.conf
• Ucomment net.ipv4.ip_forward=1
• To execute command sysctl -p

2. Create a postrouting rule within iptables:

• iptables -t nat -A POSTROUTING -o enp0s8 -s 192.168.1.0/24 -j MASQUERADE
• Where enp0s8 is WAN and 192.168.1.0/24 is LAN, please modify those parameters depend on your environment.

3. Save and restore iptables rule after reboot:

• Save rules: iptables-save > /etc/iptables.save
• Restore rules:
• Open and edit /etc/network/interfaces to add pre-up.....

# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto enp0s3
iface enp0s3 inet static
address 192.168.1.254
netmask 255.255.255.0
pre-up iptables-restore < /etc/iptables.save

Done~

如何在Ubuntu 16.04 desktop 透過PXE安裝Ubuntu?

在開始之前，請先準備與安裝相關的service在Ubuntu desktop 16.04 LTS:

準備：
1. Download Ubuntu desktop ISO
2. Download PXE bootloader

安裝：
1. DHCP Server

$ sudo apt-get install isc-dhcp-server

2. TFTP Server

$ sudo apt-get install tftpd-hpa inetutils-inetd

3. NFS Server

$ sudo apt-get install nfs-kernel-server

配置：
1. DHCP Server:

$ sudo vi /etc/dhcp/dhcpd.conf

 subnet 192.168.1.0 netmask 255.255.255.0 {
 range 192.168.1.200 192.168.1.253;
 option domain-name-servers 8.8.8.8;
 option routers 192.168.1.1;
 option broadcast-address 192.168.1.255;
 default-lease-time 600;
 max-lease-time 7200;
 next-server 192.168.1.254;
 filename "pxelinux.0";
 }

 $ sudo systemctl restart isc-dhcp-server

 2. TFTP Server:

$ sudo vi /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/var/lib/tftpboot"TFTP_ADDRESS=":69"
TFTP_OPTIONS="--secure"
RUN_DAEMON="yes"
OPTIONS="-l -s /var/lib/tftpboot"

$ sudo vi /etc/xinetd.conf

tftp    dgram   udp    wait    root    /usr/sbin/in.tftpd /usr/sbin/in.tftpd -s /var/lib/tftpboot

$ sudo systemctl restart tftpd-hpa 

3. PXE bootloader:

$ tar -xJf syslinux-6.03.tar.xz
$ cd syslinux-6.03
$ sudo cp bios/core/pxelinux.0 /var/lib/tftpboot
$ sudo cp bios/com32/lib/libcom32.c32 /var/lib/tftpboot
$ sudo cp bios/com32/libutil/libutil.c32 /var/lib/tftpboot
$ sudo cp bios/com32/elflink/ldlinux/ldlinux.c32 /var/lib/tftpboot
$ sudo cp bios/com32/menu/vesamenu.c32 /var/lib/tftpboot
$ mkdir /var/lib/tftpboot/pxelinux.cfg
$ sudo vi /var/lib/tftpboot/
pxelinux.cfg/default 

DEFAULT vesamenu.c32
MENU TITLE Network boot
LABEL ubuntu-mate-16.04.2-desktop-amd64
  MENU LABEL ubuntu-mate-16.04.2-desktop-amd64
  KERNEL vmlinuz.efi
  APPEND initrd=initrd.lz root=/dev/nfs boot=casper netboot=nfs nfsroot=192.168.1.254:/var/nfs/ubuntu_desktop splash -- 

* Remember to copy vmlinuz.efi and initrd.lz to the folder /var/lib/tftpboot from Ubuntu ISO.
* 補充: 針對18.04要修改一下設定檔如下:
  APPEND initrd=./u18/initrd_ubuntu18.04.lz root=/dev/nfs boot=casper netboot=nfs nfsroot=192.168.1.254:/var/nfs/ubuntu18.04 splash toram --

4. NFS file Server:

$ sudo mount -o loop ubuntu-16.04.3-desktop-amd64.iso /mnt/
$ sudo mkdir -p /var/nfs/ubuntu_desktop
$ sudo cp -rf /mnt/* /var/nfs/ubuntu_desktop/
$ sudo vi /etc/exports
/var/nfs/ubuntu_desktop *(ro,sync)

$ sudo systemctl restart nfs-kernel-server

$ showmount -e localhost 

Export list for localhost:
/var/nfs/ubuntu_desktop *

Boot from Network boot:

Done!

How can I move Launcher from left to the buttom on Ubuntu 16.04?

It's very simple, and it works for me even if I reboot or re-login the system b/c Ubuntu will remember it.

Steps:
1. Open a terminal

2. To execute "gsettings set com.canonical.Unity.Launcher launcher-position Bottom"

Done~

How can I get detail information of USB device?

The command lsusb, which able to list all USB devices of machine below:

lawrence@Lawrence-ThinkPad-X200:~$ lsusb
Bus 002 Device 004: ID 7392:7711 Edimax Technology Co., Ltd EW-7711UTn nLite Wireless Adapter [Ralink RT2870]
Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 008 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 007 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 006 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 003: ID 17ef:480c Lenovo Integrated Webcam
Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 002: ID 08ff:2810 AuthenTec, Inc. AES2810
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

However, I would like to know more informations. For example, speed, vendor, manufacturer......, etc. And there is a command usb-devices, which can help me.

lawrence@Lawrence-ThinkPad-X200:~$ usb-devices 

T:  Bus=02 Lev=01 Prnt=01 Port=00 Cnt=01 Dev#=  4 Spd=480 MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=7392 ProdID=7711 Rev=01.01
S:  Manufacturer=RalinkS:  Product=802.11 n WLAN
S:  SerialNumber=1.0
C:  #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=450mA
I:  If#= 0 Alt= 0 #EPs= 7 Cls=ff(vend.) Sub=ff Prot=ff Driver=rt2800usb

T:  Bus=04 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=5000 MxCh= 2
D:  Ver= 3.00 Cls=09(hub  ) Sub=00 Prot=03 MxPS= 9 #Cfgs=  1
P:  Vendor=1d6b ProdID=0003 Rev=04.13
S:  Manufacturer=Linux 4.13.0-32-generic xhci-hcd
S:  Product=xHCI Host Controller
S:  SerialNumber=0000:0d:00.0
C:  #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub

Above you can see the Spd=480/USB 2.0, and Spd=5000/USB 3.0.

[Shell script] Find user in system

The first way:

#!/bin/bash

if [ $# -eq 0 ]
then
 echo "Usage: $0 lawrence"
else
  grep "\<$1\>" /etc/passwd > /dev/null
  RETVAL=$?
  if [ $RETVAL -eq 0 ]
  then
   echo "Username $1 was found in the system"
  else
   echo "Cannot find username $1"
 fi
fi

The second way:

[ $# -eq 0 ] &&  { echo "Usage: $0 lawrence" ; exit 1; }

grep "\<$1\>" /etc/passwd > /dev/null
RETVAL=$?

[ $RETVAL -eq 0 ] && echo "Username $1 was found in the system" || echo "Cannot find username $1"

How can I add EPEL reop on CentOS 7.x?

It's quite simple, just two commands below:

# yum install epel-release

# yum repolist

Sample output: