github上的开源项目，在ubuntu系统中无法进行clone，通过在网站上注册账户，用命令生成ssh 公钥和私钥，把公钥添加到网站账户中可解决这个问题
1.产生ssh key
ssh-keygen -t rsa -b 4096 -C "xuyuan_77@163.com"
2.复制产生的pub key
若没有安装xclip的话，先安装。命令如下
sudo apt-get install xclip
用命令复制：
xclip -sel clip root/.ssh/id_rsa.pub
然后再去github 网站上添加，网站上有帮助，就不细讲了。
3.进行验证
ssh -vT git@github.com
4.把私钥加入ssh
ssh-add ~/.ssh/id_rsa
完整过程如下：
root@ubuntu:~/.ssh# ssh-keygen -t rsa -b 4096 -C "xuyuan_77@163.com"
Generating public/private rsa key pair.
Enter file in which to save the key (/root/.ssh/id_rsa): /root/.ssh/id_rsa 注意：此处不要更改其默认目录，不然验证的时候找不到private key，以至于验证通不过。至少我碰到了这个问题
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.
The key fingerprint is:
SHA256:rp5yIWGjih6xdd9Eo775MkVgFrCAQENWoFikQ25FsWw xuyuan_77@163.com
The key's randomart image is:
+---[RSA 4096]----+
|=OB*..... |
|*++ o .+ |
|=o E .o .o |
|... + o.. |
| . + + .S. |
| = o +.o. |
|.+ . +o. |
|o . . .=o |
|.. ++o+. |
+----[SHA256]-----+
root@ubuntu:~/.ssh# xclip -sel clip /root/.ssh/id_rsa.pub
root@ubuntu:~/.ssh# ssh -vT git@github.com
OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g 1 Mar 2016
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug1: Connecting to github.com [192.30.255.112] port 22.
......
debug1: Sending env LC_TIME = zh_CN.UTF-8
debug1: Sending env LC_NAME = zh_CN.UTF-8
debug1: client_input_channel_req: channel 0 rtype exit-status reply 0
Hi xuyuan77! You've successfully authenticated, but GitHub does not provide shell access.
debug1: channel 0: free: client-session, nchannels 1
Transferred: sent 3880, received 2104 bytes, in 0.4 seconds
Bytes per second: sent 9333.9, received 5061.5
debug1: Exit status 1
root@ubuntu:~/.ssh# ssh-add ~/.ssh/id_rsa
Identity added: /root/.ssh/id_rsa (/root/.ssh/id_rsa)