如何在Ubuntu上安装密码？
我的Ubuntu的是14.04 LTS。
当我安装密码学时，错误是：
Installing egg-scripts. uses namespace packages but the distribution does not require setuptools. Getting distribution for 'cryptography==0.2.1'. no previously-included directories found matching 'documentation/_build' zip_safe flag not set; analyzing archive contents... six: module references __path__ Installed /tmp/easy_install-oUz7ei/cryptography-0.2.1/.eggs/six-1.10.0-py2.7.egg Searching for cffi>=0.8 Reading https://pypi.python.org/simple/cffi/ Best match: cffi 1.5.0 Downloading https://pypi.python.org/packages/source/c/cffi/cffi-1.5.0.tar.gz#md5=dec8441e67880494ee881305059af656 Processing cffi-1.5.0.tar.gz Writing /tmp/easy_install-oUz7ei/cryptography-0.2.1/temp/easy_install-Yf2Yl3/cffi-1.5.0/setup.cfg Running cffi-1.5.0/setup.py -q bdist_egg --dist-dir /tmp/easy_install-oUz7ei/cryptography-0.2.1/temp/easy_install-Yf2Yl3/cffi-1.5.0/egg-dist-tmp-A2kjMD c/_cffi_backend.c:15:17: fatal error: ffi.h: No such file or directory #include <ffi.h> ^ compilation terminated. error: Setup script exited with error: command 'x86_64-linux-gnu-gcc' failed with exit status 1 An error occurred when trying to install cryptography 0.2.1. Look above this message for any errors that were output by easy_install. While: Installing egg-scripts. Getting distribution for 'cryptography==0.2.1'. Error: Couldn't install: cryptography 0.2.1 我不知道为什么它失败了。 是什么原因。 在Ubuntu系统上安装时是否有必要？
答案就是cryptography 安装部分的文档，这非常符合Angelos的答案：
引用它：
对于Debian和Ubuntu ，以下命令将确保安装所需的依赖关系：
$ sudo apt-get install build-essential libssl-dev libffi-dev python-dev对于Fedora和RHEL衍生产品，以下命令将确保安装所需的依赖关系：
$ sudo yum install gcc libffi-devel python-devel openssl-devel你现在应该可以用通常的方式构build和安装encryption
$ pip install cryptography
当在Ubuntu 14.04上安装encryption模块时，我遇到了同样的问题。 我通过安装libffi-dev解决了这个问题：
apt-get install -y libffi-dev
然后我得到以下错误：
build/temp.linux-x86_64-3.4/_openssl.c:431:25: fatal error: openssl/aes.h: No such file or directory #include <openssl/aes.h> ^ compilation terminated. error: command 'x86_64-linux-gnu-gcc' failed with exit status 1
我通过安装libssl-dev解决了这个问题：
apt-get install -y libssl-dev
