lsof

The lsof and fuser commands make it easy to identify the processes that are preventing you from unmounting a file system.

Depending on the operating system, lsof might be able to grab the name of the file from kernel memory.

As a systems administrator, lsof lets you peer into kernel memory to find out how the system is currently using these files.

If you suspect an application is running out of file descriptors, you can use lsof to count the number of files open to verify.

The utility to do so is called lsof, which means "list open files. "

You can use lsof to show all open files on a file system by specifying the name of the mount point.

Completes or hangs. If it hangs, then lsof will probably hang, too, and you should try to discover why ls hangs.

Listing 2 contains a script that uses lsof and netstat to show the system's current port usage in an easily readable format.

The simplest uses of lsof tell you which process has what files open and which files are opened by what process.

The rest of this article focuses on using lsof to display only the information you need and how to interpret it properly.

See Resources for information about obtaining lsof for your system.

You later discovered that lsof shows the file descriptor of a process and the associated file name.

If you're interested in knowing what files the processes owned by a particular login name have open, lsof can help.

Earlier I showed you how simply running lsof without any parameters dumps information about every open file belonging to every process.

To solve this, you need to use a command called lsof, which may need to be installed separately.

Using lsof can help you further determine which threads are accessing which files.

lsof - list open files, network connections and much more.

The lsof utility uses this information and other knowledge about the kernel's internals to produce its output.

Nmap, netstat, and lsof are the most helpful tools.

Network connections are also files, which means that lsof can also get information about them.

For information about obtaining lsof, see the Resources section.

The following appendices describe the lsof options in detail.

Listing 2 specifies three parameters to lsof.

In addition to seeing what daemons are listening, lsof can also spy on what connections are happening, again using the -i parameter.

If possible you should have a spare set of common programs such as ps, ls, if config, perhaps lsof, etc. , on a secure host.

Listing 17 provides an example of lsof, an external command.

Lsof needs a recompile to work with linux 2. 2.

You may want to consider upgrading other software such as openssl, openssh, lsof, etc at this stage.

Listing 1. Sample output of lsof