Wandering Thoughts archives

In praise of Solaris's pfiles command

I'm sure that at one point I was introduced to pfiles through a description that called it the Solaris version of lsof for a single process. This is true as far as it goes and I'm certain that I used pfiles as nothing more than this for a long time, but it understates what pfiles can do for you. This is because pfiles will give you a fair amount more information than lsof will, and much of that information is useful stuff to know.

Like lsof, pfiles will generally report what a file descriptor maps to (file, device, network connection, and Solaris IPC 'doors', often with information about what process is on the other end of the door). Unlike on some systems, the pfiles information is good enough to let you track down who is on the other end of Unix domain sockets and pipes. Sockets endpoints are usually reported directly; pipe information generally takes cross-correlating with other processes to see who else has an S_IFIFO with the specific ino open.

(You would think that getting information on the destination of Unix domain sockets would be basic information, but on some systems it can take terrible hacks.)

Pfiles will also report some socket state information for sockets, like the socket flags and the send and receive buffers. Personally I don't find this deeply useful and I wish that pfiles also showed things like the TCP window and ACK state. Fortunately you can get this protocol information with 'netstat -f inet -P tcp' or 'netstat -v -f inet -P tcp' (if you want lots of details).

Going beyond this lsof-like information, pfiles will also report various fcntl() and open() flags for the file descriptor. This will give you basic information like the FD's read/write status, but it goes beyond this; for example, you can immediately see whether or not a process has its sockets open in non-blocking mode (which can be important). This is often stuff that is not reported by other tools and having it handy can save you from needing deep dives with DTrace, a debugger, or the program source code.

(I'm sensitive to several of these issues because my recent Amanda troubleshooting left me needing to chart out the flow of pipes and to know whether some sockets were nonblocking or not. I could also have done with information on TCP window sizes at the time, but I didn't find the netstat stuff until just now. That's how it goes sometimes.)