Some novel data structure

Fountain-Coded Broadcast Distribution

Some common-sense rules or laws in the world

Schneiers Law
https://www.schneier.com/blog/archives/2011/04/schneiers_law.html

Be pythonic

The Zen of Python

    Beautiful is better than ugly.
    Explicit is better than implicit.
    Simple is better than complex.
    Complex is better than complicated.
    Flat is better than nested.
    Sparse is better than dense.
    Readability counts.
    Special cases aren't special enough to break the rules.
    Although practicality beats purity.
    Errors should never pass silently.
    Unless explicitly silenced.
    In the face of ambiguity, refuse the temptation to guess.
    There should be one-- and preferably only one --obvious way to do it.
    Although that way may not be obvious at first unless you're Dutch.
    Now is better than never.
    Although never is often better than *right* now.
    If the implementation is hard to explain, it's a bad idea.
    If the implementation is easy to explain, it may be a good idea.
    Namespaces are one honking great idea -- let's do more of those!

See https://legacy.python.org/dev/peps/pep-0020/

Python Code Style

https://docs.python-guide.org/writing/style/

Pytonic

"Pythonic" means something like "idiomatic Python"

The sense of how to use Python the right way. 

The idiom the Python language encourages.

To be Pythonic is to use the Python constructs and datastructures with clean, readable idioms.

Exploiting the features of the Python language to produce code that is clear, concise and maintainable.

https://blog.startifact.com/posts/older/what-is-pythonic.html

piVC Serversetup

piVC is a logic verfication program by Stanford University. To serve the class CS458, it requires a piVC server set up for students to use Java piVC client.

To provide better portability, the piVC server is set up in a Virtual Machine (VM) on KVM virtualization.

VM name: piVC
VM credentials: GDC convention
VM ip: 128.153.145.236

Below are the instructions on HOWTO install piVC server:

1. check out the piVC source code:

https://github.com/jgalenson/piVC

1) install svn
sudo apt-get install subversion
2) checkout source code
svn  checkout svn://www.jasonland.com/piVC
3) download yices
http://yices.csl.sri.com/download.shtml

cp   yices-1.0.40/bin/yices  ../../piVC/bin

4) install build tool
sudo apt-get install build-essential
sudo apt-get install ocaml

5) install java for the client
sudo apt-get install openjdk-7-jdk

6）compile the source code

cd piVC/src
make

7) Configure the server
check the machine ip:  ifconfig

specify the local machine static ip in piVC/conf/piVC_server.conf
dp_server_address =  xxx.xxx.xxx.xxx:4243

8) Run the service
cd piVC/bin
./both_servers

9) Config the piVC client
Download the client from here
http://cs.stanford.edu/people/jasonaue/pivc/

Run the client by
java -jar  PiVC.jar

Change the server address
Settings->Change Server Address -> xxx.xxx.xxx.xxx:4242

Run the program
Compile

Samba Server on Centos HOWTO

TDB database
root: > smbd -b | grep PRIVATE_DIR
/etc/samba

root: >smbd -b | grep LOCKDIR
/var/cache/samba

use tdbbackup utility to backup those tdb files

mkdir a directory and change its ownship
chown account.group /path/to/directory

Samba Configruation File
root: >smbd -b | grep smb.conf
/etc/samba/smb.conf

Dry run Samba Configurations
root: >testparm /etc/samba/smb.conf
root: >smbclient -L xxx.xxx.xxx.xxx(SambaServerIP) -U%

Samba valid user setup
root: >smbpasswd -a csguest
New SMB password:
Retype new SMB password:
startsmbfilepwent_internal: file /etc/samba/smbpasswd did not exist. File successfully created.
Added user csguest.

chown user.group /path/to/sambashare

Run/start/stop/restart Samba Server
root: >service smb reload
root: >service smb start
root: >service smb stop
root: >service smb condrestart

Mount Samba Share in Linux
root: >apt-get install smbfs
root: >smbmount //SambaServerIP/SambaShare /mnt/Dir -o username=account, password=pwd

Access Samba Share in WindowsXP
Control Panel -> User Accounts -> yourUserAccount
Click Manage my network passwords
Add button to enter Server, User name and Password
Server: xxx.xxx.xxx.xxx(SambaServerIP)
Username: xxx.xxx.xxx.xxx\AccountName
Password:******

My Computer -> Tools -> Map Network Drive
Folder: //SambaServerIP/SambaShare

Centos: nilfs compiling from src

Download source:
2.6.18 centos kernel source code (kernel-devel-2.6.18-128.el5.centos.plus.i686.rpm)
http://rpm.pbone.net/index.php3/stat/4/idpl/12390365/com/kernel-devel-2.6.18-128.el5.centos.plus.i686.rpm.html
kernel module source code
http://www.nilfs.org/download/nilfs-2.0.12.tar.bz2
patch for Centos
http://www.nilfs.org/pub/centos/5/SRPMS/nilfs-kmod-2.0.12-r.src.rpm
userland utilities source code
http://www.nilfs.org/download/nilfs-utils-2.0.12.tar.bz2

Required packages:
gcc
yum install gcc
e2fsprogs-devel
yum install e2fsprogs-devel

default installed: make binutils

Installation Instructions:
I. use Centos rpm installer to unpackage the kernel source code
The source code will be in the directory :
/usr/src/kernels/2.6.18-128.1.6.el5-i686

2. untar the nilfs kernel module source code and userland utilities source code
kernel module is in the directory: nilfs-2.0.12
utilities is in the directory: nilfs-utils-2.0.12

3. uncompress the nilfs-kmod-2.0.12-r.src.rpm package and copy the patch file nilfs-rhel5-kern-feature.patch to the kernel module src directory nilfs-2.0.12
_______________________________________________________

--- a/fs/kern_feature.h 2008-02-12 08:38:22.000000000 -0000
+++ b/fs/kern_feature.h 2009-04-09 12:27:24.000000000 -0000
@@ -30,6 +30,25 @@
/*
* Please define as 0/1 here if you want to override
*/
+/* for Red Hat Enterprise Linux / CentOS 5.x */
+#if defined(RHEL_MAJOR) && (RHEL_MAJOR == 5)
+# define NEED_MOUNT_SEMAPHORE 1
+# define NEED_INODE_GENERIC_IP 0
+# define NEED_INODE_BLKSIZE 0
+# define HAVE_PAGE_MKWRITE 1
+# if (RHEL_MINOR < 1)
+# define PageChecked PageFsMisc
+# define SetPageChecked SetPageFsMisc
+# define ClearPageChecked ClearPageFsMisc
+# endif
+# if (RHEL_MINOR > 0)
+# define NEED_INC_NLINK 0
+# if (RHEL_MINOR > 2)
+# define NEED_DROP_NLINK 0
+# define HAVE_LE32_64_ADD_CPU 1
+# endif
+# endif
+#endif

/*
* defaults dependent to kernel versions
_______________________________________________________

4. apply the patch to the kernel module source code
root: ~> patch -p1 < nilfs-rehel-kern-feature.patch

5. compile the kernel module source code root: ~> make
root: ~> make install

6. compile the utils source code
root: ~> make
root: ~> make install

Userful resource:
http://www.nilfs.org/download/READMEv2
http://www.cyberciti.biz/faq/appy-patch-file-using-patch-command/
http://rpm.pbone.net/index.php3/stat/4/idpl/12390365/com/kernel-devel-2.6.18-128.el5.centos.plus.i686.rpm.html
http://www.nilfs.org/en/faq.html
http://www.nilfs.org/en/pkg_centos.html

NilFS: tutorial

Nilfs is a LFS that NTT(Nippon Telegraph and Telephone Corp.) Group distributed to the Linux world. 

It has been merged into Linux mainline 2.6.30 rc-1

Below is the tutorial of how to set up a LFS partition in a VMware VM.

1. Attach multiple virtual disks to the VM in VMware

Editing virutal machine settings ->  add -> add a hard disk

 2. Install a CentOS5.1 distro in the VM and run the more than 260 updates 

(It is said CentOS5.1/5.2 are both OK. But CentOS5.0 needs to be patched.)

root : centos

3. Download the NilFS kmod and utils rpms from nilfs.org site.

i386 utilities package: http://www.nilfs.org/pub/centos/5/RPMS/i386/

i386 kernel module package: http://www.nilfs.org/pub/centos/5/RPMS/i686/

Look for the nilfs utilities : nilfs-utils-2.0.12-1.i386.rpm 

Look for the exact kernel version 2.8.18_128 : kmod-nilfs-2.0.12-2.2.6.18_128.1.6.el5.i686.rpm

the utilities and the kernel module version should match the same nilfs version and also the centos kernel version.

(It also includes PAE and Xen rpm packages in the same directory)

4. Install the NilFS rpm package

root: ~>rpm -Uvh  kmod-nilfs-2.0.12-2.6.18_128.1.6.el5.i686.rpm

5. Format the virtual disk as nilFS and mount to the system.

(The extra disk is /dev/hda)

Format the disk by mkfs command

root: ~>mkfs -t nilfs2  /dev/hda

mount the LFS disk by mount command

root: ~>mount -t nilfs2   /dev/hda      /root/nilfs

6. Use the nilFS to recover the data

Before you make some changes, you can set a checkpoint by mkcp

root: ~>mkcp

root: ~>lscp   (lscp will show what checkpoints you have)

After you make the changes, you sjhould  make the previous checkpoint to be a snapshot and then mount that previous snapshot to a new spot

root: ~>chcp  ss  5

root: ~>mount -t  nilfs2 -r -0 cp=5   /dev/hda   /root/nilfs-cp

 

nilfs.org website instructions are at the link  http://www.nilfs.org/en/about_nilfs.html (how to use nilfs --incomplete)

7. Umount nilFS disk

root: ~>umount     /root/nilfs-cp

root: ~>umount    /root/nilfs

Next --> Setup NilFS in a Xen Guest