python rrdtool install

when issue about pango,cario and libxml2 and something else
I use the following lib to fixed

https://ubuntuforums.org/showthread.php?t=1112365

that is

Install these packages:

libcairo2-dev
libpango1.0-dev
libxml2-dev 

how to use git ssh to clone a repository (permission deny )

this message us useful

when using the ssh to clone a repository, it first need to establish the rsa key pair ,that is you need to generate a key public and add this key on the remote website,
as you can see in the following instruction  "rnu  cd ~/.ssh && ssh-keygen"

and add this key on website,
after  when git clone ssh  it can verify your identification, resolving the permission deny problem

another easy to solve is use https to git clone a repository

First start by setting up your own public/private key pair set. This can use either DSA or RSA, so basically any key you setup will work. On most systems you can use ssh-keygen.

• First you'll want to cd into your .ssh directory. Open up the terminal and run:

  cd ~/.ssh && ssh-keygen

• Next you need to copy this to your clipboard.
  • On OS X run: cat id_rsa.pub | pbcopy
  • On Linux run: cat id_rsa.pub | xclip
  • On Windows (via Cygwin/Git Bash) run: cat id_rsa.pub | clip
• Add your key to your account via the website.
• Finally setup your .gitconfig.
  • git config --global user.name "bob"
  • git config --global user.email bob@... (don't forget to restart your command line to make sure the config is reloaded)

Thats it you should be good to clone and checkout.

the above message copies from

http://stackoverflow.com/questions/2643502/git-permission-denied-publickey

how to make a bootable USB which windows system installed

http://kmwoley.com/blog/creating-bootable-vista-windows-7-usb-flash-drive/  

about how to use the dd command to clone a harddisk

as the titile

this websites describes lots of things


https://wiki.archlinux.org/index.php/disk_cloning

linux bash shell export

export JJJ=1234

這就是我們要把 JJJ設定成為一個環境變數值為1234 的變數

我們發現 JJJ 要在append 新的值

可以這樣

export JJJ=$JJJ:ABCD

此時 我們的 JJJ 會變成 1234:ABCD

用 env | grep "JJJ" 可以查看一下



最後 因為 JJJ一看就是測試用的
要把它清除 可以 用 unset JJJ

Linux bash shell : set declare unset

這裡實例說明一下 set declare  unset 的功用

declare VAR=Test

設定一個變數 叫做 VAR 她的值 等於 Test
利用 set  | vim -
檢查一下目前全部的變數清單中 是否有 VAR

set -a VAR



透過 set 把 VAR 變數 定成環境變數

ene | grep "VAR"

可以利用 env 來檢查是否有設定到

如果我不想要這個變數了

unset VAR

則  env | grep "VAR" 和 set | grep "VAR"
都會被 VAR 給消除了




export 是開大絕
直接把變數丟到環境變數裡面

shell 打印訊息與錯誤訊息

./stdtest > std.log 2>&1 

以上會把  執行 stdtest 所產生的  訊息 和錯誤訊息 都印到 std.log 上面