对于一些停止维护的debian版本网络软件包资源大多停止维护，此时可以通过挂载ISO安装光盘实现本地软件包安装
apt-cdrom add
系统会提示将你要添加为源的光盘放入光驱
然后enter继续，就自动添加好了
root@214:~# apt-cdrom add
Using CD-ROM mount point /media/cdrom/
Unmounting CD-ROM...
Waiting for disc...
Please insert a Disc in the drive and press [Enter]
Mounting CD-ROM...
Identifying... [3499991a1c974d34b1f07cea4df324ac-2]
Scanning disc for index files...
Found 2 package indexes, 0 source indexes, 2 translation indexes and 0 signatures
This disc is called:
'Debian GNU/Linux 9.13.0 Stretch - Official amd64 DVD Binary-1 20200718-11:07'
Reading Package Indexes... Done
Reading Translation Indexes... Done
Writing new source list
Source list entries for this disc are:
deb cdrom:[Debian GNU/Linux 9.13.0 Stretch - Official amd64 DVD Binary-1 20200718-11:07]/ stretch contrib main
Unmounting CD-ROM...
Repeat this process for the rest of the CDs in your set.
