When attempting to install 32-bit libraries on a 64-bit CentOS 6.4 system using yum install libgcc.i686, you encountered the "protected multilib versions" error. This occurs when:

• Different architecture versions of the same package have version mismatches
• Dependency requirements conflict between packages
• System tries to maintain parallel installations of i686 and x86_64 packages

The error message clearly shows:

Protected multilib versions: libgcc-4.4.7-4.el6.i686 != libgcc-4.4.7-3.el6.x86_64

This indicates you have:

• libgcc-4.4.7-3.el6.x86_64 (64-bit version) installed
• Package manager trying to install libgcc-4.4.7-4.el6.i686 (newer 32-bit version)

1. First Attempt: Clean Update

Try updating all packages first:

yum update

Then retry the installation:

yum install libgcc.i686

2. Manual Version Synchronization

If the conflict persists, manually align versions:

yum downgrade libgcc.x86_64

Or alternatively:

yum update libgcc.x86_64

3. Advanced Resolution: Temporary Architecture Exclusion

When version alignment isn't possible:

yum install libgcc.i686 --exclude=libgcc.x86_64

Then verify the installation:

rpm -qa | grep libgcc

Create a temporary yum configuration:

echo "[main]" > /etc/yum.conf.tmp
echo "protected_multilib=false" >> /etc/yum.conf.tmp
yum -c /etc/yum.conf.tmp install libgcc.i686

Warning: This bypasses important safety checks - only use when absolutely necessary.

After successful installation, verify both architectures:

rpm -q --queryformat "%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n" libgcc

Example output should show both versions:

libgcc-4.4.7-4.el6.i686
libgcc-4.4.7-4.el6.x86_64

---

When working with CentOS 6.4, you might encounter multilib conflicts when trying to install 32-bit libraries alongside 64-bit versions. The specific error occurs when running:

yum install libgcc.i686

The error indicates three potential scenarios:

1. Missing dependencies for a libgcc upgrade
2. Multiple architectures installed with incomplete updates
3. Duplicate versions of libgcc already present

Solution 1: Diagnostic Approach

yum install libgcc.i686 --exclude libgcc.x86_64
yum check
rpm -qa | grep libgcc

Solution 2: Version Synchronization

yum update libgcc.x86_64
yum install libgcc.i686

Solution 3: Clean Installation

yum remove libgcc
yum install libgcc.i686 libgcc.x86_64

For persistent issues, examine package dependencies:

repoquery --requires libgcc.i686
yum deplist libgcc.i686

Verify repository consistency:

yum clean all
yum makecache

Manual RPM installation (if absolutely necessary):

rpm -ivh --nodeps http://vault.centos.org/6.4/os/x86_64/Packages/libgcc-4.4.7-4.el6.i686.rpm

Remember that disabling multilib protection is rarely advisable:

# Not recommended unless absolutely necessary
yum --setopt=protected_multilib=false install libgcc.i686

When developing cross-platform C++ applications, you might need both architectures:

# Compile 32-bit version
g++ -m32 hello.cpp -o hello32
# Requires libgcc.i686