GNU cfengine
3.10.2 Too many open files
In long recursive copies, where you descend into many levels of diretories,
you can quickly run out of file descriptors. The number of file descriptors
is a resource which you can often set in the shell. It is a good idea
to set this limit to a large number on a host which will be copying
a lot of files. For instance, in the C shell you would write,
Most systems should have adequate defaults for this parameter, but
on some systems it appears to be set to a low value such as 64, which is
not sufficient for large recursive tree searches.