Raspberry Pi Kernel Compilation 内核编译官方文档
elinux.org/Raspberry_Pi_Kernel_Compilation#Use_the_provided_compiler
Software & Distributions:
Software - an overview.
Distributions - operating systems and development environments for the Raspberry Pi.
Kernel Compilation - advice on compiling a kernel.
Performance - measures of the Raspberry Pi's performance.
Programming - programming languages that might be used on the Raspberry Pi.
Important note
The instructions provided below appears to outdated, are inconsistent and fail for the current version of the reffered repositories. Consider http://www.raspberrypi.org/documentation/linux/kernel/building.md, for which the cross-compilation instructions is confirmed to work. (19 March 2015, tools: 783eb21c, linux: c4ba28133).
Overview
This page explains how to rebuild the kernel image for the Raspberry Pi. There are two possible routes available:
- Compile on the Raspberry Pi itself
- Cross compile on another Linux system
Both of these routes are covered below, however, you are strongly recommended to follow the cross-compilation route. The low processing power of the Raspberry Pi means that a local compile will take many hours. A compilation of the latest kernel and modules took about 752 minutes (12h30m)!
If you want to compile an upstream kernel, rather than the Raspberry Pi Foundation's downstream kernel, please see RPi_Upstream_Kernel_Compilation for a few tips.
Example Checklist/Roadmap
This section serves to hold a new user's hand just a bit more than some of the other more generic information below in the document. To get more information on the steps in the roadmap, search this page for additional details. It assumes you can navigate filesystems, move files across systems, and have a general understanding of compiling linux kernels, filesystems, partitions, and block devices.
This series of steps yielded a successful custom/updated hardfp kernel to a stock Raspbian installation, cross compiled from an AMD 64-bit Debian system without regression on any kernel configuration options or requiring modified boot parameters. Be aware that in the worst case, you may need to overlay a stock set of kernel/modules/firmware on the Raspberry Pi if something fails. If you do not know how to do this, then a reimage of the SD card may be necessary. Assuming this is not an issue for your configuration, continue onward:
- Get the latest Raspberry Pi kernel source (https://github.com/raspberrypi/linux)
- Set an environment variable KERNEL_SRC to point to the location of the source (for example, KERNEL_SRC=/home/me/linux/ )
- Get the latest Raspberry Pi compiler (git clone https://github.com/raspberrypi/tools)
- Set an environment variable CCPREFIX to point to the location of tools (for example, CCPREFIX=/home/me/tools/arm-bcm2708/arm-bcm2708-linux-gnueabi/bin/arm-bcm2708-linux-gnueabi- )
- From the kernel clone location, clean the kernel source with "make mrproper"
- Pull the /proc/config.gz from the running Raspbian installation
- Prime the kernel with the old configuration by running "ARCH=arm CROSS_COMPILE=${CCPREFIX} make oldconfig"
- Modify the kernel configuration by either modifying the .config file or using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make menuconfig"
- Build the new kernel by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} make"
- Set an environment variable, MODULES_TEMP, to point to the location of the source (for example, MODULES_TEMP=/home/me/modules/ )
- Set aside the new kernel modules by using "ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} make modules_install"
- From the tools clone location, in the mkimage directory, run "./imagetool-uncompressed.py ${KERNEL_SRC}/arch/arm/boot/zImage"
- Move the resulting kernel.img to the Raspberry Pi's /boot/ directory
- Package up the modules into an archive such that at the top level, the structure looks like this:
- ./firmware
- ./firmware/brcm
- ./firmware/edgeport
- ./firmware/emi26
- ...
- ./modules
- ./modules/3.6.11+
- ./modules/3.6.11+/kernel
- ./modules/3.6.11+/kernel/lib
- ./modules/3.6.11+/kernel/fs
- ...
- Move the modules archive to the Raspberry Pi and extract them such that the aforementioned firmware and modules directories overwrite /lib/firmware and /lib/modules
- Get the latest Raspberry Pi firmware (git://github.com/raspberrypi/firmware.git)
- Transfer the following files from the firmware/boot directory to the Raspberry Pi /boot directory:
- bootcode.bin
- fixup.dat
- start.elf
- Transfer the firmware/hardfp/opt directory to the Raspberry Pi /opt directory
- Reboot the Raspberry Pi
The Raspberry Pi should now boot with the newly configured/recompiled kernel.
Get the kernel source
The kernel source should be downloaded from the Raspberry Pi Linux section on GitHub. Although you could just compile the vanilla kernel from Kernel.org, it will not have the necessary drivers and modules for the Broadcom SoC on the Raspberry Pi. You can however apply patches from the vanilla kernel to the Raspberry Pi one - be prepared for potential compiler grumbles though!
On Jan 2014, the current is rpi-3.10.y. You can check this and other available versions by browsing Raspberry Pi Linux section on GitHub
You can download the source directly using Git. For the 3.10 branch:
git init
git clone --depth 1 git://github.com/raspberrypi/linux.git
And for the other stable code branch, change the numbers in the following to suit:
git init
git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
git checkout rpi-3.6.y
Or you can download a tarball from the same website:
Get a compiler
Next, you will need to get a version of GCC in order to build the kernel.
1. On the Raspberry Pi
Arch Linux
pacman -Syu
pacman -S gcc make
Funtoo or Gentoo Linux
emerge make bc screen
openSUSE Linux
Detailed openSUSE Raspberry Pi 12.3 Image 20130407 + 3.8.8 kernel hack tutorial witten (2013-04-22 updated) see: http://www.raspberrypi.org/phpBB3/viewtopic.php?f=87&t=40664&p=331953#p331953 The kernel compile takes about 22 hours on Raspberry Pi Model B due massive module compiles. Include all IP_VS, ARPD, Fuse-zfs, Zram and more :-)
This works as well for Debian, Fedora Remix and others (just the package install command differs):
zypper install u-boot-tools sudo gcc automake autoconf bison gettext flex libncurses5 ncurses-devel
Raspbian and PiBang
apt-get update
apt-get -y dist-upgrade
apt-get -y install gcc make bc screen ncurses-dev
cd /usr/src
mkdir GIT; cd GIT; git init; D=`date +"%m-%d-%Y"`
git fetch git://github.com/raspberrypi/linux.git rpi-3.8.y:refs/remotes/origin/rpi-3.8.y
git checkout rpi-3.8.y
tar cpf rpi-3.8.y.$D.tar rpi-3.8.y cd /usr/src
tar xpf GIT/rpi-3.8.y.$D.tar
rm linux
ln -s linux-rpi-3.8.y linux cd /usr/src/linux
kversion=$(make -s kernelrelease)
cp linux/.config .config_$kversion cd /usr/src/
# Get config-3.8.7.ipvs+krb5+arpd.tar.bz2 from the tutorial:
wget http://www.raspberrypi.org/phpBB3/download/file.php?id=3174
# Copy the .config file to /usr/src/linux:
tar xpfj config-3.8.7.ipvs+krb5+arpd.tar.bz2 #Make the kernel and go sleep :-)
cd linux
make oldconfig
nohup make zImage dep modules & #The next day: Install it.
cd /usr/src/linux
kversion=$(make -s kernelrelease)
echo $kversion
mkdir -p /boot/$kversion
make ARCH=arm INSTALL_PATH=/boot/ install
cp System.map /boot/System.map-$kversion
cp System.map-$kversion /boot/System.map
make ARCH=arm modules_install INSTALL_MOD_PATH=/
make ARCH=arm INSTALL_PATH=/boot/ zinstall
cp .config /boot/config-$kversion
cp ./Module.symvers /boot/symvers-$kversion
cp arch/arm/boot/Image /boot/kernel.img
2. Cross compiling from Linux
Please note that when cross-compiling, your compiler may not target the correct ARM processor by default. This will at best reduce performance, or worse, compile for a much newer processor resulting in illegal instructions in your code. The pre-built compiler or a custom-built compiler are recommended because of this. (For example, the latest GCC Linaro binary targets armv7-a by default, whereas the Raspberry Pi requires armv6kz). It is possible to add extra compiler options to the HOSTCFLAGS line in Makefile. The correct flags are shown on the software page - note that you may also need to add -marm if your compiler produces Thumb code by default.
Use the provided compiler
Download the pre-built bmc2708 compiler from the Raspberry Pi tools section on GitHub.
git clone git://github.com/raspberrypi/tools.git --depth 1
Or you can download a tarball from the website using this link.
Custom-built Linaro GCC
Ubuntu
apt-get install gcc-arm-linux-gnueabi make ncurses-dev
Funtoo or Gentoo Linux
crossdev -S -v -t arm-unknown-linux-gnueabi
Crossdev should create a cross-toolchain using the latest stable versions of the required packages. If it fails, you can specify exact versions by removing the "-S" flag and adding the "--b", "--g", "--k" and "--l" flags. On 2012-05-06, cross -S -v -A gnueabi arm works just fine.
Arch Linux
yaourt -S arm-linux-gnueabi-gcc
Cross compiling from OS X
Macports
The kernel source requires a case-sensitive filesystem. If you do not have a HFS+ case-sensitive partition that can be used, create a disk image with the appropriate format. Ensure the latest versin of Xcode and command line tools are installed from Apple Developer Connection Install macports
port install arm-none-eabi-gcc
port install arm-none-eabi-binutils
If you get an error message that elf.h is missing
sudo port install libelf && sudo ln -s /opt/local/include/libelf /usr/include/libelf
From opensource.apple.com, download and copy elf.h and elftypes.h to /usr/include
Edit elf.h and add
#define EM_S390 22
#define R_386_NONE 0
#define R_386_32 1
#define R_386_PC32 2
#define R_ARM_NONE 0
#define R_ARM_PC24 1
#define R_ARM_ABS32 2
#define R_MIPS_NONE 0
#define R_MIPS_16 1
#define R_MIPS_32 2
#define R_MIPS_REL32 3
#define R_MIPS_26 4
#define R_MIPS_HI16 5
#define R_MIPS_LO16 6
#define EM_S390 22
#define R_MIPS_64 18
#define R_390_64 22
#define R_X86_64_64 1
#define R_SPARC_64 32
#define R_SH_DIR32 1
#define R_PPC_ADDR32 1
#define R_PPC64_ADDR64 38
#define R_IA64_IMM64 0x23
If you get a "SEGMENT_SIZE is undeclared" error open the Makefile and change the line:
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include)
to
NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) -Dlinux
Complete script requires raspberrypi.config to be in the same folder that you execute from.
sudo port install arm-none-eabi-gcc
sudo port install arm-none-eabi-binutils
sudo port install libelf && sudo ln -s /opt/local/include/libelf /usr/include/libelf
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elftypes.h?txt -o /usr/include/elftypes.h
sudo curl http://opensource.apple.com/source/dtrace/dtrace-48/sys/elf.h?txt -o /usr/include/elf.h
#code to append to elf.h
echo "
#define EM_S390 22
#define R_386_NONE 0
#define R_386_32 1
#define R_386_PC32 2
#define R_ARM_NONE 0
#define R_ARM_PC24 1
#define R_ARM_ABS32 2
#define R_MIPS_NONE 0
#define R_MIPS_16 1
#define R_MIPS_32 2
#define R_MIPS_REL32 3
#define R_MIPS_26 4
#define R_MIPS_HI16 5
#define R_MIPS_LO16 6
#define EM_S390 22
#define R_MIPS_64 18
#define R_390_64 22
#define R_X86_64_64 1
#define R_SPARC_64 32
#define R_SH_DIR32 1
#define R_PPC_ADDR32 1
#define R_PPC64_ADDR64 38
#define R_IA64_IMM64 0x23" > elf-append.h
sudo -s 'cat elf-append.h >> /usr/include/elf.h' #Make a case sensitive 3 GB disk image, raspberrypi-kernel, and attach it:
hdiutil create -size 10g -type SPARSEBUNDLE -nospotlight -volname raspberrypi-kernel -fs "Case-sensitive Journaled HFS+" -attach ./raspberrypi-kernel.dmg
cp raspberrypi.config /Volumes/raspberrypi-kernel/
mkdir /Volumes/raspberrypi-kernel/src
cd /Volumes/raspberrypi-kernel/src #Get source, either 1. from a ZIP file (faster), or 2. from Git
#1. From a ZIP file
curl https://codeload.github.com/raspberrypi/linux/zip/rpi-3.6.y -o ./rpi-3.6.y.zip
unzip rpi-3.6.y.zip
#2. From Git (disabled)
#git init
#git fetch git://github.com/raspberrypi/linux.git rpi-3.6.y:refs/remotes/origin/rpi-3.6.y
#git checkout rpi-3.6.y cpu=$(sysctl hw.ncpu | awk '{print $2}')
cpup1=$((cpu+1)) cd /Volumes/raspberrypi-kernel/src/linux-rpi-3.6.y/
export CCPREFIX=/opt/local/bin/arm-none-eabi-
make mrproper
cp /Volumes/raspberrypi-kernel/raspberrypi.config .config
#Answer yes to all config options
#yes "" | make ARCH=arm CROSS_COMPILE=${CCPREFIX} oldconfig
make ARCH=arm CROSS_COMPILE=${CCPREFIX} -j$cpup1
#make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules -j$cpup1
Yagarto
Download and install from here.
Perform the compilation
Firstly, ensure your build directory is clean:
make mrproper
Next, in all cases, you will want to get a working kernel configuration to start from. You can get the one running on the Raspberry Pi by typing the following (on the Raspberry Pi):
zcat /proc/config.gz > .config
Then copy .config into your build directory.
Alternatively, the default configuration is available in the downloaded kernel source in arch/arm/configs/bcmrpi_defconfig. Just copy this to .config in the build directory.
From this point on, if you are cross-compiling, set an environment variable CCPREFIX that points to the prefix of your compiler binary as each compiler will be named slightly differently.
export CCPREFIX=/path/to/your/compiler/binary/prefix-of-binary-
If you are building on the Raspberry Pi, remove ARCH=arm CROSS_COMPILE=${CCPREFIX} from each command.
Ensure that your configuration file is up-to-date:
make ARCH=arm CROSS_COMPILE=${CCPREFIX} oldconfig
If any configuration options have been added, you will be asked what set each option to. If you don't know the answer, just press enter to accept the default.
Optionally, if you want to make changes to the configuration, run this next:
make ARCH=arm CROSS_COMPILE=${CCPREFIX} menuconfig
Now you are ready to build:
(On the Raspberry Pi, type 'screen' to open a virtual screen. If you use
it you can disconnect from the Raspberry Pi and compile overnight...)
make ARCH=arm CROSS_COMPILE=${CCPREFIX}
If you are on a multi-core system, you can make the build faster by appending -j<N> where <N> is the number of cores on your system plus one (that is, -j3 for two cores).
Find something else to get on with while the compilation takes place. On an average PC with the default configuration, this should take about 15 minutes.
The modules will be build with the following command.
make ARCH=arm CROSS_COMPILE=${CCPREFIX} modules
Transfer the build
The fully built kernel will be arch/arm/boot/Image. Copy your new kernel file into the Raspberry Pi boot partition, though preferably as a new file (such as kernel_new.img) just in case it doesn't work. If you're building on the Raspberry Pi, just copy the file to /boot. If you use a different filename, edit config.txt change the kernel line:
kernel=kernel_new.img
#kernel=kernel.img
Now you need to transfer the modules. Set an environment variable that points to a temporary module path.
export MODULES_TEMP=~/modules
In the build directory, run the following command:
make ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} modules_install
The contents of this directory, a single
lib
directory, should then be copied into the Raspberry Pi root directory, merging or overwriting
/lib
NOTE: If you have rebuilt the new kernel with exactly the same version as the one that's running, you'll need to remove the old modules first. Ideally this should be done offline by mounting the SD card on another system.
NOTE: The lib directory will have symlinks back to the kernel sources (lib/modules/<kernel-version>/source and lib/modules/<kernel-version>/build). If you have limited space on the SD card and don't intend to compile modules on the Raspberry Pi itself, you will probably want to remove those links before you transfer the lib directory. The size difference can be many hundreds of MB.
Your Raspberry Pi should now be ready to boot the new kernel. However, at this point it's recommended that you update your GPU firmware and libraries. This is required if you've just moved from 3.2 to 3.6 as the firmware interface has changed.
Get the firmware
The firmware and boot files should be updated at the same time to ensure that your new kernel works properly. Again, two branches are available:
- master - This is the version of firmware currently used in Raspbian (that is, it works with the 3.2 kernel).
- next - This is a development branch which provides a newer GPU firmware to work with the updated drivers in the 3.6 kernel.
You can either download the source directly using Git: You can download the firmware directly using Git. For the master branch:
git clone git://github.com/raspberrypi/firmware.git
And for the next branch:
git fetch git://github.com/raspberrypi/firmware.git next:refs/remotes/origin/next
Or you can download a tarball from the website using these links: master next
Transfer the firmware
Firstly, update the required boot files in the Raspberry Pi boot directory with those you've downloaded. These are:
- bootcode.bin
- fixup.dat
- start.elf
Next, you need to copy the VC libraries over. There are two copies of this: one for hard float and one for soft float. To find the correct one, run the following command:
${CCPREFIX}gcc -v 2>&1 | grep hard
If something prints out, and you can see --with-float=hard, you need the hard float ones. NOTE: The current version of Raspbian uses hard float.
Remove the /opt/vc directory from the Raspberry Pi root, then:
- For hard float, copy vc from the hardfp/opt directory into /opt in the Raspberry Pi root directory
- Otherwise copy vc from the top-level opt directory into /opt in the Raspberry Pi root directory.
Note: The hard float vs soft float here refers only to the kernel itself, not the functionality it provides. Your applications will still be able to use hard floats. The kernel doesn't use floats anyway, so it is not something to worry about as long as you select the correct vc directory to copy.
Test your build
Power cycle your Raspberry Pi and check the following:
- If you have the serial port on the GPIO expander wired up, you should see the kernel booting.
- The screen works - the kernel boots and you get a login prompt.
- The VC interface is working - if the 'OK' LED flashes regularly eight or so times every few seconds once the OS has booted, it's not. You can also test this by running vcgencmd measure_temp. If it prints "VCHI initialization failed", you have the a mismatch between the firmware, the VC libraries, and the kernel driver.
- Run uname -a and check that your new kernel is the one that's running.
- Make sure you don't have any odd error messages during boot that may indicate a module isn't working properly. If you see missed completion of cmd 18 regarding DMA transfers to the SD card, you can safely ignore it.
Build modules for the running kernel
You need the kernel sources for the currently running kernel to successfully build kernel modules for the Raspberry Pi. More specifically, only parts of the complete source, the so called kernel headers are needed. There are two ways to arrive at a state from which you can build kernel modules on the Raspberry Pi.
1. is most suitable if you have been using Kernel sources from raspberrypi.org
2. is using only mainline kernel stuff
1. Using rpi-source
rpi-source downloads a matching source for the running kernel.
It supports rpi-update kernels and Raspian kernels.
Examples: https://github.com/notro/rpi-source/wiki/Examples-on-how-to-build-various-modules
2. Manually
If you have used or want to stick with a vanilla (mainline) kernel, there is a different way
You have been following the RPi_Upstream_Kernel_Compilation
guide, correct? Great, let's move on: That guide is not using modules,
so enable modules in make menuconfig first. Then execute
$ ARCH=arm CROSS_COMPILE=${CCPREFIX} chrt -i 0 make -j 8
$ ARCH=arm CROSS_COMPILE=${CCPREFIX} INSTALL_MOD_PATH=${MODULES_TEMP} make modules_install
The second line will create the .ko files and it will create the necessary folder structure (/usr/src/linux/lib/modules/`uname -r`/[build|kernel|source]. build and source are symlinks to the kernel sources. kernel contains the module files (under some subdirectories).
Now you can continue with RPi_Upstream_Kernel_Compilation compiling the bootloader and so on. Finally also copy the used kernel sources onto the SD card, e.g. under /home/pi/linux
$ cp -av /usr/src/linux/ <sdcard-ext4-root>/home/pi/
Boot the Raspberry Pi, then execute
$ cd /home/pi
$ sudo chown -R pi:pi linux/
to change back ownership to you (this is necessary unless your username on your build machine is also "pi"...). Now copy /home/pi/linux/lib/modules/* to the correct
$ sudo cp -R /home/pi/linux/lib/modules/`uname -r`/ /lib/modules/
Correct the symlinks:
$ sudo cd /lib/modules/`uname -r`/
$ sudo rm build source
$ ln -s /home/pi/linux build
$ ln -s /home/pi/linux source
Now, we need to fix one more problem: During the cross-compilation build, a couple scripts were compiled for the host. We also need them for the Raspberry Pi. Still on the Pi, this can be checked with e.g.
$ file /home/pi/linux/scripts/recordmcount (returns something with x86-64)
$ cd /home/pi/linux/
$ make scripts
$ file /home/pi/linux/scripts/recordmcount (now returns something with 32-bit and ARM)
Raspberry Pi Kernel Compilation 内核编译官方文档的更多相关文章
- The Linux Kernel 4.15.0官方文档内核语言风格解读(留)
https://www.kernel.org/doc/html/v4.15/translations/zh_CN/coding-style.html 1.缩进 制表符是 8 个字符,所以缩进也是 8 ...
- 从LFS官方文档构建完整Linux系统
从LFS官方文档构建完整Linux系统 http://www.cnblogs.com/sonofdark/p/4962609.html 这不是新手教程!!! Parallels Desktop (为防 ...
- [dpdk] 读官方文档(1)
前提:已读了这本书<<深入浅出dpdk(朱清河等著)>>. 目标:读官方文档,同时跟着文档进行安装编译等工作. http://dpdk.org/doc/guides/index ...
- Cuda 9.2 CuDnn7.0 官方文档解读
目录 Cuda 9.2 CuDnn7.0 官方文档解读 准备工作(下载) 显卡驱动重装 CUDA安装 系统要求 处理之前安装的cuda文件 下载的deb安装过程 下载的runfile的安装过程 安装完 ...
- Google Android官方文档进程与线程(Processes and Threads)翻译
android的多线程在开发中已经有使用过了,想再系统地学习一下,找到了android的官方文档,介绍进程与线程的介绍,试着翻译一下. 原文地址:http://developer.android.co ...
- 五个新知识:微软SHA2补丁,亚信专业工具,微软官方文档,使用过期签名(附官方推荐链接),注意使用具有UAC的CMD
五个新知识:微软SHA2补丁,亚信专业工具,微软官方文档,使用过期签名 不支持SHA2算法的计算机更新补丁:https://technet.microsoft.com/zh-CN/library/se ...
- centos7安装oracle11g(根据oracle官方文档安装,解决图形界面安装问题)
一.系统及安装包 操作系统:centos 7.4 oracle版本:oracle 11g r2 二.centos环境配置 安装数据库所需要的软件包 [root@localhost data]# yum ...
- Akka Typed 官方文档之随手记
️ 引言 近两年,一直在折腾用FP与OO共存的编程语言Scala,采取以函数式编程为主的方式,结合TDD和BDD的手段,采用Domain Driven Design的方法学,去构造DDDD应用(Dom ...
- Kotlin开发语言文档(官方文档)-- 目录
开始阅读Kotlin官方文档.先上文档目录.有些内容还未阅读,有些目录标目翻译还需琢磨琢磨.后续再将具体内容的链接逐步加上. 文档链接:https://kotlinlang.org/docs/kotl ...
随机推荐
- utf8转为gb2312的函数
from:http://blog.csdn.net/qianguozheng/article/details/46429245 // 代码转换操作类 class CodeConverter { pri ...
- ci 多个文件同时上传
// 单个文件请手册,这里多个文件中,参数设置可参考手册 view 视图 <form...> <input type="file" name="user ...
- html5 canvas绘制圆形印章,以及与页面交互
<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title> ...
- 让你的 Node.js 应用跑得更快的 10 个技巧
Node.js 受益于它的事件驱动和异步的特征,已经很快了.但是,在现代网络中只是快是不行的.如果你打算用 Node.js 开发你的下一个Web 应用的话,那么你就应该无所不用其极,让你的应用更快,异 ...
- mysql中char与varchar的区别
在建立数据库表结构的时候,为了给一个String类型的数据定义一个数据库的数据库类型,一般参考的都是char或者varchar,这两种选择有时候让人很纠结,今天想总结一下它们两者的区别,明确一下选择塔 ...
- sudo: unable to resolve host XXX 解决方法
执行sudo命令时候,总是提示sudo: unable to resolve host xxx 解决方法: 法1. 在/etc/hosts/添加hosts映射, 如127.0.0.1 xxx 法2. ...
- yii学习随感
最近我们公司信易网络在用yii开发一个项目自己临时学习了一下yii 把学习感悟和大家一起分享一下 Yii Framework是一个基于组件.用于开发大型 Web 应用的高性能 PHP 框架.Yii提供 ...
- web2py相关-------------------------------(一)初遇
在第一次换工作的时候,希望转行 做编程,就面试了很多家,很多人问我 懂不懂html 书写,我非常诚实的告诉他们不会. 当然那时我很天真的认为,只要自己愿意学习这些都不是问题,事实证明人的学习能力是很快 ...
- cygwin下的第一次编程记录
今天在window7上安装了cygwin,体验了一把unix,编了个小c,c++程序 先把过程记录下来 1.先删除以前建立的source文件夹 rm -rf source linux删除目录很简单,很 ...
- poj 1144 Network
Network 题意:输入n(n < 100)个点,不一定是连通图,问有多少个割点? 割点:删除某个点之后,图的联通分量增加. 思路:dfs利用时间戳dfs_clock的特性,点u的low函数l ...