The lsof utility - 'list open files'

Version/Environment (if relevant): Applicable to any Linux-based system including Domino deployments.

Issue:

Administrators and engineers need to identify processes holding file locks, investigate socket activity, or troubleshoot process ID (PID) conflicts on a Linux-based system.

Root Cause:

This is a reference article for the lsof utility.

Resolution:

What is lsof?

lsof lists open files on Linux-based systems. It displays information about file descriptors and the processes that hold them open, including network connections and listening ports. Use lsof to identify processes holding file locks, investigate socket activity, and troubleshoot process ID (PID) conflicts.

⚠️ Prerequisite: lsof may require privilege elevation to access files belonging to other users. Prepend sudo to any command when running as a non-root user.

Basic usage Use the following commands to troubleshoot open files on a Linux system: Find all open files for a user:

lsof -u <username>

Find all open files associated with a particular process using a PID:

lsof -p <PID>

List and locate all open socket files:

lsof +D / -a -d sock

Locate all open files listening on a specific port:

lsof -i :<port number>

Identify all open files linked to an application by program name:

lsof -c <program name>

Advanced usage Use these commands for more targeted investigation across processes, file descriptors, and time intervals: Display the process name, PID, and file name for all open files at a set time interval:

lsof -n -r <time interval> +L -F pn -F f

Locate all open files for a specific process at a set time interval and sort by PID:

lsof -p <PID> -n -r <time interval> +L -s

Find all open files and the command line that opened them:

lsof -c <command name> -a -c <command name> +L1

Find all open files linked to a specific file descriptor:

lsof -a -d <file descriptor>

Notes/Information:

lsof can also help identify processes blocking a filesystem unmount. Running lsof <filesystem_name> will display all open files on the named filesystem.
lsof +L1 can be used to find unlinked open files on local disks — files that have been deleted but are still held open by a process, which can cause unexpected disk usage.

​Issue:

​Root Cause:

​Resolution:

​What is lsof?

​Notes/Information:

Issue:

Root Cause:

Resolution:

What is lsof?

Notes/Information: