Após atualizar o Ubuntu para a versão 8.04, o servidor do postgre não iniciava mais com o seguinte erro:
* The PostgreSQL server failed to start. Please check the log output: BRT LOG: could not load root certificate file "root.crt": no SSL error reported BRT DETAIL: Will not verify client certificates. BRT FATAL: could not create shared memory segment: Invalid argument BRT DETAIL: Failed system call was shmget(key=5432001, size=34504704, 03600). BRT HINT: This error usually means that PostgreSQL's request for a shared memory segment exceeded your kernel's SHMMAX parameter. You can either reduce the request size or reconfigure the kernel with larger SHMMAX. To reduce the request size (currently 34504704 bytes), reduce PostgreSQL's shared_buffers parameter (currently 3456) and/or its max_connections parameter (currently 103). If the request size is already small, it's possible that it is less than your kernel's SHMMIN parameter, in which case raising the request size or reconfiguring SHMMIN is called for. The PostgreSQL documentation contains more information about shared memory configuration.
Foi necessário alterar o arquivo “/etc/postgresql/8.3/main/postgresql.conf”, trocando o valor da variável “shared_buffers” de “32MB” para “26MB”.