Build a debian package and upload to Launchpad ppa

  1. Create Launchpad PPA at https://launchpad.net/people/+me/+activate-ppa
  2. Creating your OpenPGP keys with gpg command

    • Open a terminal and type:
      gpg --gen-key
      
    • GPG will now ask you a number of questions about the type of key you want to generate. follow the steps below to select the default option each time.
    • Check that your key has been generated by typing gpg --list-keys and, if successful. pub 1024D/12345678 -> this is the important number
    • Launchpad doesn't store your key directly, so you need to export your public key to a key server, such as keyserver.ubuntu.com:
      gpg --keyserver keyserver.ubuntu.com --send-keys 12345678
      Replace 12345678 with the pub id you noted in step 3.
      
      If successful, GPG will display a message similar to:
      gpg: sending key 12345678 to hkp server keyserver.ubuntu.com
      Importing your key into Launchpad with gpg
      
  3. Add OpenPGP key to Launchpad

    • Launchpad identifies your OpenPGP key by its fingerprint. In your terminal, you can ask GPG for your key's fingerprint by typing:
      gpg --fingerprint
      
      GPG will display a message similar to:
        Key fingerprint = 0464 39CD 2486 190A 2C5A  0739 0E68 04DC 16E7 CB72
      copy only the numeric fingerprint: 0464 39CD 2486 190A 2C5A 0739 0E68 04DC 16E7 CB72.
      
    • Visit your OpenPGP key page at https://launchpad.net/people/+me/+editpgpkeys
    • Paste the fingerprint that you copied in step 1 into the Fingerprint text-box, then click the Import Key button. Launchpad will use the fingerprint to check the Ubuntu key server for your key and, if successful, send you an encrypted email asking you to confirm the key import. (Note : this is a brief ... from launchpad process..... both process take a while so just take your time...)
  4. set ~/.devscripts

    DEBUILD_DPKG_BUILDPACKAGE_OPTS="-us -I -i"
    DEBUILD_LINTIAN_OPTS="-i -I --show-overrides"
    
  5. get source

    apt-get build-dep lshw
    bzr lp:ubuntu/trusty/lshw
    dch -v X.XtestVersion -D trusty
    debuild -S
    
  6. upload changes to launchpad's ppa and push code

    dput ppa:swem/ppa xxxxxxxxxxxxxxxxxx_source.changes
    bzr push lp:~swem/totem/trunk
    

Extra: Build debian package on your own machine

pbuilder-dist trusty amd64 create
pbuilder-dist trusty amd64 build xxxxxxxxxxxxxxxxxx_source.dsc

Check ~/pbuilder/trusty_result/, the xxxxxxxxxxxxxxxxxx.deb should be there.

Ref:

An expert is a person who has made all the mistakes that can be made in a very narrow field

Brendan Gregg,是一位 Computer performance analyst,前幾個月很有名的那張 Linux Performance Observability Tools 就是他作的。(Linux Performance Tools at LinuxCon North America 2014)

今天在網路上看到他的書裡的一段話,滿受到激勵的。資訊技術發展到現在已是博大精深,每個系統深入下去了解都有很大的學問,學習的過程難免遇到挫折、犯錯,但這些累積,就是成為專家的過程。

For a beginner, feeling lost when you’re studying a performance issue can be discouraging. This feeling, too, is normal: you will feel lost, you will make mistakes, and you will often be wrong.
Quoting Niels Bohr, a Danish physicist:
An expert is a person who has made all the mistakes that can be made in a very narrow field.
By telling you stories like this one, I hope to reassure you that mistakes and wrong turns are normal (even for the best of us) and to show you some techniques and methodologies to help you find your way.”

Brendan,Gregg. “Systems Performance: Enterprise and the Cloud.” Pearson Education, 2013-10-07。

Xvfb (X virtual framebuffer)

最近才知道原來有 X virtual framebuffer 這種東西,可以在 Linux Server 端先把畫面 render 好,而 Client 端只要準備好 VNC Client,就可以連過去使用。啟動 X virtual framebuffer 與 x11vnc,並且開啟 window manager 與簡單的 gnome-panel 範例如下,初步試了一下滿順暢的(我跟server之間的 Round-trip time 約 38 ms):

(以下範例的 vnc port 為6000,登入密碼為 pass)

Xvfb :33 -screen 0 800x600x16 &
x11vnc -storepasswd pass ~/.vnc/passwd
x11vnc -display :33 -geometry 800x600 -rfbauth ~/.vnc/passwd -forever -rfbport 6000 -httpport 6001 &
export DISPLAY=:33
openbox-session &
gnome-panel &

Ref.

  1. fcwu/docker-ubuntu-vnc-desktop
  2. Xvfb - Wikipedia

使用 qemu (or KVM) 建立 debian VM

有很多工具可以用來建立 Virtual Machine ,例如 VirtualBox, VMware, LXC, Qemu, Qemu with KVM, Xen 等等。

QEMU - Debian Wiki 簡單的介紹了如何使用 Qemu 來運行虛擬環境

使用現有 Image

Debian developer Aurelien Jarno 提供了數個預先建立的 Image https://people.debian.org/~aurel32/qemu/,這邊我使用 amd64 的架構做示範幾種啟動虛擬環境的方式:

  • 開啟 QEMU,預設使用 SDL 顯示 guest OS 的畫面

    qemu-system-x86_64 -hda debian_wheezy_amd64_standard.qcow2 -m 256
    
  • 開啟 QEMU,使用 terminal 操作虛擬環境 (一般PC上開機約180秒)

    qemu-system-x86_64 -hda debian_wheezy_amd64_standard.qcow2 -m 256 -curses
    
  • 開啟QEMU,並將 host OS port 5555 的封包轉送給 Guest OS 的 port 80

    qemu-system-x86_64 -hda debian_wheezy_amd64_standard.qcow2 -m 256 -curses -redir tcp:5555::80
    
  • 開啟QEMU,並且開啟 kvm full virtualization support。如果 kernel,processor 有支援,將大大提昇虛擬環境運行速度。這項操作需 root 權限。 (一般PC上開機約30秒,可大大看出 -enable-kvm 的差異)

    qemu-system-x86_64 -hda debian_wheezy_amd64_standard.qcow2 -m 256 -curses -enable-kvm
    

特別注意的是我這邊沒有特別對網路做設定,根據 Documentation ,TCP, UDP可以運作,但ICMP 不會。我實際測試的結果確實是如此。(Note - if you are using the (default) SLiRP user networking, then ping (ICMP) will not work, though TCP and UDP will. Don't try to use ping to test your QEMU network configuration!)

自已建立 qemu image

  1. 建立虛擬硬碟
    dd if=/dev/zero of=rootfs.img bs=1G count=2
    
  2. 格式化虛擬硬碟為 ext4
    mkfs.ext4 rootfs.img
    
  3. mount 虛擬硬碟 (需要 root 權限)
    mount -o loop rootfs.img /mnt
    
  4. 執行 debootstrap (需要 root 權限)
    debootstrap --no-check-gpg --arch=amd64 wheezy /mnt/ http://debian.nctu.edu.tw/debian/
    
  5. 查詢虛擬硬碟的 UUID,我這邊是"4cc6834a-df20-4cb3-ad55-79433346e000"
    blkid rootfs.img
    

rootfs.img: UUID="4cc6834a-df20-4cb3-ad55-79433346e000" TYPE="ext4"

  1. 填寫 /etc/fstab,讓虛擬機開機時就會 mount 虛擬硬碟
    echo "UUID=4cc6834a-df20-4cb3-ad55-79433346e000 / ext4 0 1" >> /mnt/etc/fstab
    
  2. chroot 進 /mnt,安裝 linux kernel,安裝並設定 grub bootloader。結束後退出 chroot 環境。(需root權限)
    chroot /mnt
    apt-get update
    apt-get install -y linux-image-amd64
    apt-get install -y grub-pc
    grub-install /dev/hda
    update-grub
    exit
    
  3. umount 虛擬硬碟 (需 root 權限)
    umount /mnt
    

至此,rootfs.img裡面就是一個完整的 debian OS 了。可以用前面所說的方法,以 qemu 開啟。也可以將這個虛擬硬碟轉換為 qcow2 格式,可以佔用較小空間(但虛擬作業系統跑起來的時候則需多花一些計算效能)。

qemu-img convert -f raw -O qcow2 rootfs.img mydebian.qcow2

Ref:

Update:
Linaro 有提供 Debian Jessie 8.0 的 image: http://images.validation.linaro.org/kvm/jessie.img.gz

在 Archlinux 上啟動Avahi-daemon

這篇回覆介紹了如何在 Archlinux 上使用 systemd 來開啟 avahi-daemon,使得區域網路內的電腦可以用 .local 來連線到其它電腦。

  1. pacman -S avahi nss-mdns Installs the Avahi services daemon and the Multicast DNS resolver. nano /etc/nsswitch.conf This file tells the C library how to obtain name-service information.
  2. Change the line hosts: files dns myhostname to hosts: files mdns_minimal [NOTFOUND=return] dns myhostname, save and exit.
  3. systemctl start avahi-daemon Starts the Avahi service manually since we're already booted.look for errors)
  4. systemctl enable avahi-daemon Enables the Avahi service on boot.

How do I get to use .local hostnames with Arch Linux?

用python fcntl 取得 file lock

在 Stack Overflow 上看到的問答。稍微修改了一下為可執行的版本,下面的Python程式碼可以對一個檔案做lock。同時執行2個這樣的 python script,先取得 file lock 的 process 可以順利印出 "No error",沒取得 file lock 的 process 則會得到 IOError, 印出 "can't immediately lock the file" 後結束程式。

#!/usr/bin/env python

# -*- coding: utf-8 -*-

import fcntl
import time
f = open('/tmp/locktest', 'r')
try:
    fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
except IOError:
    print("can't immediately lock the file")
else:
    print("No error")
    time.sleep(10)
f.close()

先取得 file lock 的 process:

# python test.py

No error

沒取得 file lock 的 process:

# python test.py

can't immediately lock the file

離 Python System Programming 更近一步了!

Ref: Python fcntl does not lock as expected

Setup Domain Controller on Ubuntu 14.04

在ubuntu 14.04 上架設 Samba Domain Controller 的步驟:

  1. 安裝 samba libpam-smbpass

    sudo apt-get install samba libpam-smbpass
    

    samba 版本目前是4.1.6 (4.0以上的 Samba 才有提供 Domain Controller 的功能)

    samba -V
    Version 4.1.6-Ubuntu
    
  2. 使用 samba-tool 一步一步設定,這裡我規劃 samba domain 的網域為 mysamba.test.io

    samba-tool domain provision --use-rfc2307 --interactive
    

設定成功,過程的設定記錄如下:

vagrant@vagrant-ubuntu-trusty-64:~$ sudo samba-tool domain provision --use-rfc2307 --interactive                                                   
Realm: mysamba.test.io
 Domain [mysamba]: 
 Server Role (dc, member, standalone) [dc]: 
 DNS backend (SAMBA_INTERNAL, BIND9_FLATFILE, BIND9_DLZ, NONE) [SAMBA_INTERNAL]: 
 DNS forwarder IP address (write 'none' to disable forwarding) [192.168.1.253]: 192.168.1.253
Administrator password: 
Retype password: 
Looking up IPv4 addresses
More than one IPv4 address found. Using 192.168.1.2
Looking up IPv6 addresses
No IPv6 address will be assigned
Setting up secrets.ldb
Setting up the registry
Setting up the privileges database
Setting up idmap db
Setting up SAM db
Setting up sam.ldb partitions and settings
Setting up sam.ldb rootDSE
Pre-loading the Samba 4 and AD schema
Adding DomainDN: DC=mysamba,DC=test,DC=io
Adding configuration container
Setting up sam.ldb schema
Setting up sam.ldb configuration data
Setting up display specifiers
Modifying display specifiers
Adding users container
Modifying users container
Adding computers container
Modifying computers container
Setting up sam.ldb data
Setting up well known security principals
Setting up sam.ldb users and groups
Setting up self join
Adding DNS accounts
Creating CN=MicrosoftDNS,CN=System,DC=mysamba,DC=test,DC=io
Creating DomainDnsZones and ForestDnsZones partitions
Populating DomainDnsZones and ForestDnsZones partitions
Setting up sam.ldb rootDSE marking as synchronized
Fixing provision GUIDs
A Kerberos configuration suitable for Samba 4 has been generated at /var/lib/samba/private/krb5.conf
Setting up fake yp server settings
Once the above files are installed, your Samba4 server will be ready to use
Server Role:           active directory domain controller
Hostname:              vagrant-ubuntu-trusty-64
NetBIOS Domain:        MYSAMBA
DNS Domain:            mysamba.test.io
DOMAIN SID:            S-1-5-21-711469164-2329730621-2401598146

附註:在使用 samba-tool 的過程式如果有設定錯誤,想再進行一行 samba-tool 操作,會出現錯誤訊息,提示你必須把 /var/lib/samba/private/sam.ldb /etc/samba/smb.conf 刪除,讓 samba-tool 來重新建立

sudo rm /var/lib/samba/private/sam.ldb
sudo rm /etc/samba/smb.conf

Ref: Samba AD DC HOWTO

編譯 Upstart 1.13.2

編譯 Upstart 1.13.2:

sudo apt-get install libnih-dbus-dev libjson-c-dev
cd upstart 1.13.2/
./configure
make

編譯完成後,會得到以下的執行檔,這樣就得到一組 userspace 上開關機所需要的 utility 了

init/init
util/initctl
util/reboot
util/runlevel
shutdown
telinit
upstart-event-bridge
upstart--bridge
upstart-dbus-bridge
upstart-socket-bridge
upstart-local-bridge