每次我通过终端在 KDE neon 中安装新软件包时都会收到此消息，这是否正常，我应该忽略它还是应该解决这个问题？
Reading package lists... Done
Building dependency tree
Reading state information... Done
Starting pkgProblemResolver with broken count: 0
Starting 2 pkgProblemResolver with broken count: 0
Done
The following NEW packages will be installed:
tree
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/43.0 kB of archives.
After this operation, 115 kB of additional disk space will be used.
Selecting previously unselected package tree.
(Reading database ... 280095 files and directories currently installed.)
Preparing to unpack .../tree_1.8.0-1_amd64.deb ...
Unpacking tree (1.8.0-1) ...
Setting up tree (1.8.0-1) ...
Processing triggers for man-db (2.9.1-1) ...
Not building database; man-db/auto-update is not 'true'.
答案1
警告只是警告；这意味着mandb安装相关软件包时不会运行它，其结果是手册页索引缓存不会更新。
警告的技术原因是缺少/var/lib/man-db/auto-update.我不确定是什么原因造成的。要恢复man-db触发器，请恢复该文件：
sudo touch /var/lib/man-db/auto-update
您将不再看到警告，并且缓存将被更新。您可以自己更新缓存：
sudo mandb -pq
答案2
删除旧的 mandb 索引：
sudo rm -rf /var/cache/man/*
重新生成它：
sudo mandb -c
或者将您的设备连接到交流电源然后运行（需要几分钟）：
sudo systemctl restart man-db.service
然后检查man-db.service
systemctl status man-db.service
答案3
检查你的 debconf 设置：
bash# debconf-show man-db
* man-db/install-setuid: false
man-db/auto-update: false
更改设置并重新配置包：
echo "set man-db/auto-update true" | sudo debconf-communicate
sudo dpkg-reconfigure man-db