CentOS 6.6自带的是Python 2.6.6，而编译llvm需要Python 2.7以上。
checking for python...
which python
/usr/bin/python
python -V
Python 2.6.6
yum中最新的也是Python 2.6.6，只能下载Python 2.7.12的源代码自己编译安装。
操作步骤如下：
1）安装devtoolset
yum groupinstall "Development tools"
2）安装编译Python需要的包包
yum install zlib-devel bzip2-devel openssl-devel ncurses-devel sqlite-devel
3）下载并解压Python 2.7.12的源代码
cd /opt
wget --no-check-certificate https://www.python.org/ftp/python/2.7.12/Python-2.7.12.tar.xz
wget https://www.python.org/ftp/python/2.7.8/Python-2.7.8.tar.xz
#如果tar版本过低，请使用xz -d xx.tar.xz 然后 tar -xf xxx.tar
tar -xvf Python-2.7.12.tar.xz
cd Python-2.7.12
4）编译与安装Python 2.7.12
./configure --prefix=/opt/python27
make && make altinstall
5）将python命令指向Python 2.7.12
#备份老python
mv /usr/bin/python /usr/bin/python2.6.6
#建立软连接
ln -s /opt/python27/bin/python2.7 /usr/bin/python
升级python以后yum的使用可能会受到影响，需要进行一下设置
vi /usr/bin/yum
找到第一行 #!/usr/bin/python 改为 #!/usr/bin/python2.6.6
至此升级完成！
6）检查Python版本
python -V
Python 2.7.12
make install 的几种情况
Let's take a look at the generated Makefile!
First, the install target:
install: altinstall bininstall maninstall
It does everythingaltinstalldoes, along withbininstallandmaninstall
Here'sbininstall, it just creates thepythonand other symbolic links.
# Install the interpreter by creating a symlink chain:
# $(PYTHON) -> python2 -> python$(VERSION))
# Also create equivalent chains for other installed files
bininstall: altbininstall
-if test -f $(DESTDIR)$(BINDIR)/$(PYTHON) -o -h $(DESTDIR)$(BINDIR)/$(PYTHON); \
then rm -f $(DESTDIR)$(BINDIR)/$(PYTHON); \
else true; \
fi
(cd $(DESTDIR)$(BINDIR); $(LN) -s python2$(EXE) $(PYTHON))
-rm -f $(DESTDIR)$(BINDIR)/python2$(EXE)
(cd $(DESTDIR)$(BINDIR); $(LN) -s python$(VERSION)$(EXE) python2$(EXE))
... (More links created)
And here'smaninstall, it just creates "unversioned" links to the python manual pages.
# Install the unversioned manual pages
maninstall: altmaninstall
-rm -f $(DESTDIR)$(MANDIR)/man1/python2.1
(cd $(DESTDIR)$(MANDIR)/man1; $(LN) -s python$(VERSION).1 python2.1)
-rm -f $(DESTDIR)$(MANDIR)/man1/python.1
(cd $(DESTDIR)$(MANDIR)/man1; $(LN) -s python2.1 python.1)
Tl;dr:altinstallskips creating thepythonlink and the manual pages links,installwill hide the system binaries and manual pages.
