I installed debian9 from DVD,and the chinese input fcitx doesn't work ,
and aptitude update doesn't eigher,163 sources,as follows:
忽略 cdrom://[Debian GNU/Linux 9.0.0 _Stretch_ - Official amd64 DVD Binary-1 20170617-13:08] stretch InRelease
错误 cdrom://[Debian GNU/Linux 9.0.0 _Stretch_ - Official amd64 DVD Binary-1 20170617-13:08] stretch Release
请使用 apt-cdrom，通过它可以让 APT 识别该盘片。apt-get upgdate 不能被用来加入新的盘片。
忽略 http://mirrors.163.com/debian stretch InRelease
读取： 1 http://mirrors.163.com/debian stretch-updates InRelease [88.5 kB]
读取： 2 http://mirrors.163.com/debian stretch-backports InRelease [87.3 kB]
读取： 3 http://mirrors.163.com/debian-security stretch/updates InRelease [62.9 kB]
读取： 4 http://mirrors.163.com/debian stretch Release [113 kB]
100% [正在工作]
and 100% for hours.
and how to insert picture?
there is no problem with network

here are some suggestion maybe useful for you:
1.edit /etc/apt/sources.list ,add "non-free contrib" to the end of deb and deb-src line;
2. run command "apt update && apt upgrade"
3.run conmmand "apt install fcitx"
4.install "sougou-pinyin for linux" ，this package canbe download from sohu official website.
5.restart your computor.
now you can use "ctrl+space" to change input-method and try to input chinese in firefox,and try to input chinese in kde(or gnome or other),if it doesn't work in kde,follow 6
6.install "fcitx fcitx-bin fcitx-config-common fcitx-config-gtk fcitx-data fcitx-frontend-all fcitx-frontend-gtk2 fcitx-frontend-gtk3 fcitx-frontend-qt4 fcitx-frontend-qt5:amd64 fcitx-module-cloudpinyin:amd64 fcitx-module-dbus fcitx-module-kimpanel fcitx-module-lua fcitx-module-x11 fcitx-modules fcitx-sunpinyin fcitx-ui-classic libfcitx-config4:amd64 libfcitx-core0:amd64 libfcitx-gclient0:amd64 libfcitx-qt5-1:amd64 libfcitx-utils0:amd64 "

1.编辑 /etc/apt/sources.list ，每行末尾添加 non-free contrib
2.使用命令"apt update && apt upgrade"更新系统
3.使用命令 "apt install fcitx" 安装fcitx，
4安装搜狗拼音输入法，去搜狐官网下载
5.重启电脑
6.使用搜狗输入法，看看能不能输入汉字。有可能在浏览器中能输入汉字，但是kde或者gnome中不能输入汉字，不能输入汉字时，使用软件管理器安装如下依赖（上面以列出）并重启

去网易镜像站点复制源文件把原来源文件覆盖掉