Updated from 4:39 p.m. EST

Red Hat ( RHAT) doubled its profit and generated more cash in the fourth quarter than Wall Street expected, the Linux software company reported after Tuesday's closing bell.

But the company's EPS guidance for the first quarter was a penny shy of expectations, and in after-hours trading on Instinet shares were off $1.11, or nearly 4%, to $27.70.

Sales were in line with Wall Street's estimates at $78.7 million, an increase of 37% year over year. Net income was $27.3 million, or 13 cents a share, compared with $11.8 million, or 7 cents a share a year ago. Analysts polled by Thomson First Call were looking for an EPS of 12 cents.

The company did not disclose its bookings, a closely watched metric, for the February quarter, and left it to analysts to derive a number.

Billings (revenue plus the change in deferred revenue) were $102.5 million, up 40% year over year and up 16% sequentially. The number would have been even higher, CEO Mathew J. Szulik said on a call with analysts, if a customer who has signed a "mid-seven-figure" deal had not asked to postpone billing for one quarter.

Cash generated by operating activities was $50 million, down sequentially from $54 million but still more than the $45 million to $50 million analysts had expected.

Operating income increased by 165% to $19.8 million; operating margins improved to 25% from 13% a year ago.

Subscription revenue was up 44% to $66.7 million. The company's total deferred revenue balance was $223.5 million, an increase of 63% over the same quarter last year and up 12% sequentially.

Szulik said that Linux continues to replace Unix deployments, a trend that began some time ago, and is now winning share from Windows, although that trend is still in its early stages.