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DK Bose
Asked: 2019-10-23 01:51:15 +0800 CST

Why do lines with "c-n-f Metadata" appear in the output of `sudo apt update`?

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Kubuntu 19.10

I can't say when this began, but the output of sudo apt update has lines with c-n-f Metadata.

...                                                       
Hit:11 http://ppa.launchpad.net/kubuntu-ppa/backports/ubuntu eoan InRelease                                                  
Get:12 http://security.ubuntu.com/ubuntu eoan-security/main amd64 c-n-f Metadata [232 B]               
Get:13 http://security.ubuntu.com/ubuntu eoan-security/universe amd64 Packages [2,404 B]
Get:14 http://security.ubuntu.com/ubuntu eoan-security/universe amd64 c-n-f Metadata [288 B]
Fetched 445 kB in 2s (195 kB/s)                         
Reading package lists... Done
...

I found please add cnf support to debmirror indicating that cnf expands to "Command not found" but after reading that I'm none the wiser in understanding its purpose in sudo apt update. What is it's purpose?

updates apt

1 Answers

  1. The Ubuntu (21.04) package command-not-found contains /etc/apt/apt.conf.d/50command-not-found which makes apt(8) check for the c-n-f Metadata entries in the repositories when updating.

    If this is installed, bash(1) & zsh(1) shells will produce a suggestion along with the error message for missing commands, e.g.:

    user@ubuntu:~$ rogue
Command 'rogue' not found, but can be installed with:
sudo apt install bsdgames-nonfree
user@ubuntu:~$

    Ubuntu's bash(1) global config file /etc/bash.bashrc checks for command-not-found and loads handler routines for it if present.

    The downloaded commands are stored in /var/lib/apt/lists/*_cnf_Commands (as mentioned by kulfy)
    The aggregated data is stored in /var/lib/command-not-found/ in SQLite/json.

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