How do I get the arm64 man pages locally?

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Summary

A developer requested how to access ldr manual pages locally on an ARM64 system, similar to the online version, or via Vim’s K key. The root cause was the missing ldr binary and its corresponding manual page on the host system. The solution involves either installing the specific package containing the tool, creating a custom local man page, or configuring Vim to use a web-based fallback for documentation lookups. This highlights that local man and Vim’s K command rely entirely on local filesystem resources.

Root Cause

The immediate failure stems from two dependencies not being met on the user’s system:

  • Missing Binary: The command ldr is not standard in most Linux distributions. It typically belongs to specific toolchains (e.g., binutils or vendor SDKs). If the binary isn’t installed, the system has no context for its documentation.
  • Missing Man Page Database: man looks for pre-formatted pages (usually in /usr/share/man/). If the package for the tool isn’t installed, the associated .gz man page file does not exist.
  • Vim Configuration: Vim’s K (keyword lookup) defaults to man or :help. If K is unconfigured or the word under the cursor has no local entry, it fails.

Why This Happens in Real Systems

  • Decentralized Installation: ARM64 environments vary wildly (Android, Ubuntu Server, embedded Linux). Tools like ldr are often proprietary or part of vendor-specific SDKs that do not automatically populate the global man database.
  • Minimal Containers: In DevOps/CI pipelines, images are stripped down to essentials. If binutils or documentation packages are excluded to save space, man lookups will fail for even standard tools.
  • Vim Defaults: Vim is conservative. It does not automatically route documentation requests to the web because that requires network access and specific browser integration, which might be unavailable or insecure in restricted environments.

Real-World Impact

  • Decreased Developer Velocity: Developers waste time searching the web instead of getting immediate context, breaking their flow state.
  • Offline Inaccessibility: Engineers working in secure, air-gapped, or offline environments cannot access critical documentation if it is not cached locally.
  • Tooling Friction: “Magic” editor features (like K) failing leads to frustration and a perception that the environment is “broken” or unstable.

Example or Code

If you need to provide documentation for a custom or missing tool immediately, you can generate a local man page source file and view it. Save the following content as ldr.1:

.TH LDR 1 "October 2023" "Version 1.0" "User Commands"
.SH NAME
ldr \- Linker Description Resource utility
.SH SYNOPSIS
.B ldr
[\fIOPTION\fR]... \fIFILE\fR...
.SH DESCRIPTION
Parse and link resource files for the ARM64 architecture.
.SH OPTIONS
.TP
.B \-v
Output version information and exit.
.TP
.B \-h
Display help message.
.SH SEE ALSO
.BR ld (1),
.BR gcc (1)
.SH AUTHOR
Written by the DevOps Team.

To view it immediately (assuming the file is in the current directory):

mkdir -p ~/man/man1
cp ldr.1 ~/man/man1/
export MANPATH=~/man:$MANPATH
man ldr

To make Vim’s K use a web fallback (requires lynx or similar):

:set keywordprg=:!lynx\ https://docs.example.com/search?q=

How Senior Engineers Fix It

Senior engineers prioritize immediate workflow restoration and long-term consistency:

  • Immediate Fix (Editor): Modify Vim configuration (~/.vimrc) to map K to a shell command that opens the specific URL in a browser or fetches text via curl. 
    " In ~/.vimrc
set keywordprg=:!open_browser.sh\ https://kernel.org/search?q=
  • Systemic Fix (OS): Identify the package containing the tool and install it, then verify the MANPATH. 
    # Example for Debian/Ubuntu if ldr was part of binutils
sudo apt update && sudo apt install binutils
man -f ldr
  • Documentation Fix: If the tool is internal, create a man page source, check it into version control, and ensure the CI/CD pipeline installs it to /usr/share/man/ on all developer images.

Why Juniors Miss It

  • Assumption of Standardization: Juniors often assume that every Linux command is standard and should be available everywhere.
  • Lack of Awareness of man Internals: They don’t realize that man is just a file viewer looking for files in specific directories defined by $MANPATH.
  • Search-First Mentality: They immediately reach for a browser rather than checking the local filesystem (which ldr, ls /usr/bin/ldr) first.
  • Editor Configuration Gaps: Juniors are often users of their editor, not configurators. They don’t know that keywordprg exists or how to modify ~/.vimrc to change the behavior of K.