Both Xubunut and Kubuntu are ubuntu distributions, but the desktop environment is different, and the source is the same.
1. Backup
sudo cp -p /etc/apt/sources.list /etc/apt/sources.list.bak backup the original sorce file
sudo vi/vim /etc/apt/sources.list Modify sources.list file editor.
2. Add mirror source
sudo vim /etc/apt/sources.list
Add Ali, University of Science and Technology mirror source
# USTC image source deb https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-updates main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-backports main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-security main restricted universe multiverse deb https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse deb-src https://mirrors.ustc.edu.cn/ubuntu/ bionic-proposed main restricted universe multiverse # Ali image source deb http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse deb http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-security main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-updates main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-proposed main restricted universe multiverse deb-src http://mirrors.aliyun.com/ubuntu/ bionic-backports main restricted universe multiverse # Tsinghua mirror source # By default, the source image is commented to improve the speed of apt update, if necessary, you can uncomment it yourself deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-updates main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-backports main restricted universe multiverse deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-security main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-security main restricted universe multiverse # Pre-release software source, not recommended to enable # deb https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse # deb-src https://mirrors.tuna.tsinghua.edu.cn/ubuntu/ trusty-proposed main restricted universe multiverse #Foreign source (source for installing Ubuntu) deb http://archive.ubuntu.com/ubuntu/ bionic main restricted # deb-src http://archive.ubuntu.com/ubuntu/ bionic main restricted .....
Copy the above image source to sources.list and save it.
3, sudo aptitude/apt-get update update source
sudo aptitude/apt-get update sudo aptitude/apt-get upgrade Execute the above two source changes
sudo aptitude/apt-get update
This command will visit each URL in the source list, read the software list, and then save it on the local computer. The software list we see in the Synaptic package manager is updated through the update command.
After the update, you may need to upgrade.
sudo aptitude/apt-get upgrade
This command will compare the locally installed software with the corresponding software in the newly downloaded software list. If the installed software version is found to be too low, it will prompt you to update. If your software is the latest version, it will prompt:
0 packages were upgraded, 0 packages were newly installed, 0 packages were to be uninstalled, and 0 packages were not upgraded.
All in all, update is to update the software list, and upgrade is to update the software.