Updating installing-rust.md - add ldconfig workaround on install

[j1n3l0]

Add a workaround for the error (I twice personally have) observed when following the installation instructions:

nelo@HP-EliteBook-8540w:~$ curl -sf -L https://static.rust-lang.org/rustup.sh | sudo sh
[sudo] password for nelo: 
rustup: gpg available. signatures will be verified
rustup: downloading manifest for 'beta'
gpg: WARNING: unsafe ownership on configuration file `/home/nelo/.gnupg/gpg.conf'
rustup: downloading toolchain for 'beta'
######################################################################## 100.0%
gpg: WARNING: unsafe ownership on configuration file `/home/nelo/.gnupg/gpg.conf'
gpg: WARNING: unsafe ownership on configuration file `/home/nelo/.gnupg/gpg.conf'
gpg: Signature made Fri 17 Apr 2015 04:07:37 BST using RSA key ID 7B3B09DC
gpg: Good signature from "Rust Language (Tag and Release Signing Key) <rust-key@rust-lang.org>"
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: 108F 6620 5EAE B0AA A8DD  5E1C 85AB 96E6 FA1B E5FE
     Subkey fingerprint: C134 66B7 E169 A085 1886  3216 5CB4 A934 7B3B 09DC
rustup: extracting installer
rustup: installing toolchain for 'beta'
install: creating uninstall script at /usr/local/lib/rustlib/uninstall.sh
install: installing component 'rustc'
install: installing component 'cargo'
install: installing component 'rust-docs'

    Rust is ready to roll.

nelo@HP-EliteBook-8540w:~$ rustc --version
rustc: error while loading shared libraries: librustc_driver-4e7c5e5c.so: cannot open shared object file: No such file or directory
nelo@HP-EliteBook-8540w:~$ sudo ldconfig
nelo@HP-EliteBook-8540w:~$ rustc --version
rustc 1.0.0-beta.2 (e9080ec39 2015-04-16) (built 2015-04-16)
nelo@HP-EliteBook-8540w:~$ uname -a
Linux HP-EliteBook-8540w 3.13.0-49-generic #83-Ubuntu SMP Fri Apr 10 20:11:33 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

A better fix would be to work out why we appear to need to run ldconfig before the install works. If you agree then perhaps this can be changed into an issue and the docs left alone?

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @pcwalton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. The way Github handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see CONTRIBUTING.md for more information.

[alexcrichton]

r? @brson

[brson]

This must be a bug in rust-installer, since it is supposed to be running ldconfig, and I would much prefer to fix it. What Linux distro and version are you running?

[steveklabnik]

We've gotten lots of people in IRC over the last two or three weeks I'd say who needed to run ldconfig to get their install working.

[brson]

Yuck. I will investigate this problem very soon.

[brson]

There's a related issue where Fedora does not configure the dynamic linker to look in /usr/local/lib so ldconfig doesn't work, but that doesn't seem to be case here since a subsequent invocation does work: rust-lang/rust-installer#30

[j1n3l0]

@brson

• my work laptop (as in the comment above):

Linux HP-EliteBook-8540w 3.13.0-49-generic #83-Ubuntu SMP Fri Apr 10 20:11:33 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

• my home laptop:

Linux j1n3l0-Ideapad-Z570 3.11.0-18-generic #32-Ubuntu SMP Tue Feb 18 21:13:28 UTC 2014 i686 i686 i686 GNU/Linux

Both have Ubuntu 14.04 running on them.

[mdinger]

This looks pretty similar to rust-lang/rustup#3

[brson]

The underlying issue has been fixed in rustup rust-lang/rustup@fa82250. Thanks for the patch and report.

[j1n3l0]

I can confirm it works. Thanks.