When I try to compile bitcoind on a Ubuntu 10.04 machine I do:

make -f makefile.unix 

but get errors such as:

In file included from db.cpp:6:
db.h:14:20: warning: db_cxx.h: No such file or directory
In file included from db.cpp:6:
db.h:42: error: 'DbEnv' does not name a type

I wonder what could be the error. In mac os x, I could compile it wothout problem.