You must seed RPM with a new source, which is depedendent on your RedHat version:
RHEL/CentOS 5.5
shell> sudo wget -O/etc/yum.repos.d/couchbase.repo \ http://packages.couchbase.com/rpm/couchbase-centos55-i386.repo shell> sudo wget -O/etc/yum.repos.d/couchbase.repo \ http://packages.couchbase.com/rpm/couchbase-centos55-x86_64.repo
RHEL/CentOS 6.2
shell> sudo wget -O/etc/yum.repos.d/couchbase.repo \ http://packages.couchbase.com/rpm/couchbase-centos62-i686.repo shell> sudo wget -O/etc/yum.repos.d/couchbase.repo \ http://packages.couchbase.com/rpm/couchbase-centos62-x86_64.repo
Then to install libcouchbase itself, run:
shell> sudo yum check-update shell> sudo yum install -y libcouchbase2 libcouchbase-devel