Overview
fuser outputs the PIDs of processes that are using a specified file, directory, or network port. This allows you to easily identify which processes are occupying specific resources and, if necessary, terminate those processes.
Key Features
- Identify processes using files/directories
- Identify processes using network ports (TCP/UDP)
- Provides functionality to forcefully terminate identified processes
- Check for processes using a mount point before unmounting
Key Options
The main options of the fuser command help to configure various aspects of process identification and control.
Basic Operations
Output Formats
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Description:
`fuser` Executes the command.
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Usage Examples
Effectively manage processes using file and network resources with various usage examples of the fuser command.
Find processes using a specific file
fuser /var/log/syslogFind the PIDs of processes using the `/var/log/syslog` file.
Find processes using a mount point
fuser -m /mnt/usb_driveFind all processes using the `/mnt/usb_drive` mount point.
Find processes using a specific TCP port
fuser -n tcp 80Find the PIDs of processes using TCP port 80 (HTTP).
View detailed information with user names
fuser -uv /home/user/document.txtDisplay detailed PIDs and usernames of processes using the `/home/user/document.txt` file.
Forcefully terminate processes using a file
sudo fuser -k /tmp/locked_file.txtForcefully terminate all processes using the `/tmp/locked_file.txt` file. (Caution: Using this on critical processes may lead to system instability)
Terminate processes using a specific UDP port
sudo fuser -k -n udp 53Forcefully terminate processes using UDP port 53 (DNS).
Installation
fuser is typically installed by default as part of the `psmisc` package on most Linux distributions. If fuser is not present on your system, you can install it using the following commands.
Debian/Ubuntu
sudo apt update && sudo apt install psmiscInstall using the apt package manager.
CentOS/RHEL/Fedora
sudo yum install psmisc
# or
sudo dnf install psmiscInstall using the yum or dnf package manager.
Tips & Precautions
Useful tips and precautions when using the fuser command.
Caution when using fuser -k
The `-k` option forcefully terminates processes. Using it on critical system processes can lead to system instability or data loss. Carefully check which processes will be terminated before using it.
- Recommendation: First, run `fuser` without the `-k` option to see which processes are affected, and then use the `-k` option only if necessary.
Comparison with lsof
Both fuser and lsof are used to find processes using open files and sockets, but they differ in their purpose and output format.
- fuser: Primarily specialized for quickly finding the PIDs of processes using specific files/sockets.
- lsof: Provides much more detailed information about open files and has a wide range of filtering and output options.
Permission Issues
You may need `sudo` privileges to check or terminate system files, other users' processes, or specific network ports.
- Permissions: In most cases, it is recommended to run `fuser` using `sudo`.