1.establish the situation of vx6
explain:my system is Ubuntu 16.04 x86_64
step 1:sudo apt-get install glibc-devel.i686(maybe this step will fail,but this is no problem)
step2:sudo apt-get qemu(if it is failed,you use "sudo apt-get update",then you can execute it)
step3:
mkdir -p ~/xv6 && cd ~/xv6
git clone git://github.com/mit-pdos/xv6-public.git(I get this from the website:https://pdos.csail.mit.edu/6.828/2014/xv6.html)
step4:cd xv6-public(you can use"ls",find the directory)
step5:make
step6:qemu-system-i386 -serial mon:stdio -hdb fs.img xv6.img -smp 1 -m 512
if you are in the qemu situation,you are success.
tip:you edit"vi ~/.bashrc",write " alias qemu='qemu-system-i386 -serial mon:stdio -hdb fs.img xv6.img -smp 1 -m 512' " in the final row ,for the convinence.
2.program the module system call-date, and use it like date.
https://pdos.csail.mit.edu/6.828/2016/homework/xv6-syscall.html
sudo apt install git; git --version
git clone git://github.com/mit-pdos/xv6-public.git
sudo apt install libsdl1.2-dev
sudo apt install qemu
sudo ln -s /usr/bin/qemu /usr/bin/qemu-system-x86_64
make qemu