作者：hankf，Xilinx Employee
在Ubuntu 16.04下，安装petalinux需要的软件包遇到错误，“requested an impossible situation”。安装Ubuntu 16.04时，选择的地区是上海。据说选择香港不会有这个问题。
user@:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 16.04.6 LTS Release: 16.04 Codename: xenial $ uname -a Linux 4.15.0-48-generic #51~16.04.1-Ubuntu SMP Fri Apr 5 12:01:12 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux user@:~$ sudo apt install zlib1g:i386 Reading package lists... Done Building dependency tree Reading state information... Done Some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: mount : PreDepends: libblkid1 (>= 2.17.2) but it is not going to be installed PreDepends: libmount1 (>= 2.25) but it is not going to be installed zlib1g:i386 : Depends: libc6:i386 (>= 2.4) but it is not going to be installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.
在网页 https://blog.csdn.net/H_O_W_E/article/details/81879319 提到，用香港的源可以解决问题。我在/etc/apt/source.list里使用香港源(hk.archive.ubuntu.com)或者新加坡源(sg.archive.ubuntu.com)，依然遇到同样问题。
deb http://hk.archive.ubuntu.com/ubuntu/ xenial main restricted # deb http://sg.archive.ubuntu.com/ubuntu/ xenial main restricted # deb http://cn.archive.ubuntu.com/ubuntu/ xenial main restricted deb http://hk.archive.ubuntu.com/ubuntu/ xenial universe # deb http://sg.archive.ubuntu.com/ubuntu/ xenial universe # deb http://cn.archive.ubuntu.com/ubuntu/ xenial universe deb http://hk.archive.ubuntu.com/ubuntu/ xenial multiverse deb http://sg.archive.ubuntu.com/ubuntu/ xenial multiverse # deb http://cn.archive.ubuntu.com/ubuntu/ xenial multiverse
更改为清华的源后，可以正常安装。在文件/etc/apt/source.list里增加下列行。
# deb cdrom:[Ubuntu 16.04 LTS _Xenial Xerus_ - Release amd64 (20160420.1)]/ xenial main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-updates multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-backports main restricted universe multiverse deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security main restricted deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security universe deb http://mirrors.tuna.tsinghua.edu.cn/ubuntu/ xenial-security multiverse
然后执行sudo apt-get update，再重新安装，可以正常安装petalinux需要的软件包。
下面是Ubutnu 16.04下安装petalinux的所有软件包的命令。
sudo apt-get install -y tofrodos iproute2 gawk xvfb gcc-4.8 wget \ build-essential checkinstall libreadline-gplv2-dev \ libncursesw5-dev libssl-dev libsqlite3-dev tk-dev \ libgdbm-dev libc6-dev libbz2-dev git make net-tools libncurses5-dev \ tftpd zlib1g-dev libssl-dev flex bison libselinux1 gnupg diffstat \ chrpath socat xterm autoconf libtool tar unzip texinfo \ gcc-multilib libsdl1.2-dev libglib2.0-dev screen pax gzip \ language-pack-en libtool-bin cpio lib32z1 lsb-release zlib1g:i386 \ vim-common libgtk2.0-dev libstdc++6:i386 libc6:i386
