Changing the CHOST Wernfried Haas Chris White This document explains how to change the CHOST of an existing system. As this is a fundamental change to your system and can seriously damage your system, it is vital to follow these instructions very closely. 1.0 2006-09-13 Introduction

Changing the CHOST is a big issue that can seriously screw up your system - so why is there a guide for that it at all?

There are certain situations where changing the CHOST is inevitable, e.g. if you want to upgrade to glibc 2.4 which only supports nptl and you find out that your CHOST is i386, which makes it impossible to use nptl. In this case, you don't have a lot of options, and changing CHOST is one of them.

Even if following these instructions problems may arise, so please make sure to read and execute them very carefully. In this example the CHOST will be changed from i386 to i686, it is likely you do another change, please change the commands accordingly.

Changing the CHOST
Building The Packages

To start out with the CHOST change, edit the file /etc/make.conf and change CHOST value to suit your needs. Then, rebuild the following packages in this order: 

# emerge -av1 binutils gcc glibc
Verifying Things Work

Now it is time to make sure that your gcc-config/binutils-config settings are sane and you dont have any leftovers left behind in /etc/env.d/.

The output of gcc-config and binutils-config should look like this (may differ according to your gcc version and chost, gcc 4.1.1 and i686 here): 

# gcc-config -l
 [1] i686-pc-linux-gnu-4.1.1 *
# gcc-config -c
i686-pc-linux-gnu-4.1.1

# binutils-config -l
 [1] i686-pc-linux-gnu-2.16.1 *
# binutils-config -c
i686-pc-linux-gnu-2.16.1

# (Now take a look around /etc/env.d/)
# cd /etc/env.d/

Next, check to see if there are references to the old CHOST: 

# grep 386 *
05gcc-i386-pc-linux-gnu:PATH="/usr/i386-pc-linux-gnu/gcc-bin/4.1.1"
05gcc-i386-pc-linux-gnu:ROOTPATH="/usr/i386-pc-linux-gnu/gcc-bin/4.1.1"
This may not happen to you, but in this case 05gcc-i386-pc-linux-gnu contains references to the old CHOST. Things may look differently on your system depending on which CHOST you are changing to/from, or even be just fine. The name may also be 05gcc-your_new_CHOST-pc-linux-gnu.

Before deleting the file, let's check for files with the updated CHOST: 

# grep 686 * 
05binutils:MANPATH=/usr/share/binutils-data/i686-pc-linux-gnu/2.16.1/man
05binutils:INFOPATH=/usr/share/binutils-data/i686-pc-linux-gnu/2.16.1/info
05binutils:LDPATH=/usr/i686-pc-linux-gnu/lib
05gcc:PATH="/usr/i686-pc-linux-gnu/gcc-bin/4.1.1"
05gcc:ROOTPATH="/usr/i686-pc-linux-gnu/gcc-bin/4.1.1"
05gcc:MANPATH="/usr/share/gcc-data/i686-pc-linux-gnu/4.1.1/man"
05gcc:INFOPATH="/usr/share/gcc-data/i686-pc-linux-gnu/4.1.1/info"
05gcc:LDPATH="/usr/lib/gcc/i686-pc-linux-gnu/4.1.1"

This one looks good as there should always be only one file for gcc in /etc/env.d/ (05gcc in this example), so let's delete the one with the wrong references: 

# rm 05gcc-i386-pc-linux-gnu

The same also applies to binutils - if there's an extra one, see which is the outdated one and delete it. Next, check your /etc/env.d/binutils/ 

# cd /etc/env.d/binutils/
# ls -la
total 8
-rw-r--r-- 1 root root  15 Sep  3 13:48 config-i686-pc-linux-gnu
-rw-r--r-- 1 root root 126 Sep  3 13:48 i686-pc-linux-gnu-2.16.1

# cat config-i686-pc-linux-gnu
CURRENT=2.16.1
# cat i686-pc-linux-gnu-2.16.1
TARGET="i686-pc-linux-gnu"
VER="2.16.1"
LIBPATH="/usr/lib/binutils/i686-pc-linux-gnu/2.16.1"
FAKE_TARGETS="i686-pc-linux-gnu"

That one looks good, those two files actually should be there. Time to move on to the gcc directory. 

# cd /etc/env.d/gcc
# ls -la
total 12
-rw-r--r-- 1 root root  32 Sep  3 16:43 config
-rw-r--r-- 1 root root  32 Aug  3 14:25 config-i386-pc-linux-gnu
-rw-r--r-- 1 root root 292 Sep  3 16:43 i686-pc-linux-gnu-4.1.1

# cat config
CURRENT=i686-pc-linux-gnu-4.1.1

# cat config-i386-pc-linux-gnu
CURRENT=i386-pc-linux-gnu-4.1.1

# cat i686-pc-linux-gnu-4.1.1
PATH="/usr/i686-pc-linux-gnu/gcc-bin/4.1.1"
ROOTPATH="/usr/i686-pc-linux-gnu/gcc-bin/4.1.1"
LDPATH="/usr/lib/gcc/i686-pc-linux-gnu/4.1.1"
GCCBITS="32"
MANPATH="/usr/share/gcc-data/i686-pc-linux-gnu/4.1.1/man"
INFOPATH="/usr/share/gcc-data/i686-pc-linux-gnu/4.1.1/info"
STDCXX_INCDIR="g++-v4"

config and i686-pc-linux-gnu-4.1.1 are fine, but config-i386-pc-linux-gnu is another leftover that needs removal.

Again, the name of the file containing references to an outdated gcc version may have a different name, e.g. config-i686-pc-linux-gnu even though you are changing to i686. It is important you identify the file on its content, not only the name. 
# rm config-i386-pc-linux-gnu

now run: 

# env-update && source /etc/profile

Then verify everything is fixed: 

# grep -r 386 /etc/env.d/

If you still find something, you must have missed some file, try to track it down before going on.

Finishing The Change

Now it is necessary to re-emerge libtool and run fix_libtool_files.sh. Make sure to use the correct gcc version (your current one, 4.1.1 here, and the old architecture (i386 here)). 

# emerge -av1 libtool
# fix_libtool_files.sh 4.1.1 --oldarch i386-pc-linux-gnu

You may want to run: 

# emerge -e world

Now, in theory it should not be necessary to do so, but it can not be 100% guaranteed that this is actually the case. ;-) If you do not recompile the world target, i've been told at least some packages need recompiling, so you should do: 

# emerge -av1 python

All packages using perl install to the CHOST directory and hence need remerging. In case you haven't installed qfile, you will need to install app-portage/portage-utils first

# emerge -av portage-utils
# emerge -av1 `qfile /usr/lib/perl* -Cq | sort -u`

A bunch of programs have been said to need recompiling as well, such as groff, courier, telnet and others. 

error while loading shared libraries: libstdc++.so.5: cannot open shared object file: No such file or directory
This is not related to changing the CHOST, but a consequence of upgrading gcc. Please read the gcc upgrade guide and rebuild the packages accordingly.

If you encounter other packages that need recompiling, please let me know at the the email below.

That should be all, feedback (both if it worked, failed or other problems were encountered) is welcome, please send an email to amne@gentoo.org or post to this forums thread. Much in this howto comes from vapier, thanks for your help!