Master Linux System Inspection: lsmod, lsof, lspci & lsscsi Explained with Real Examples

1. lsmod command

The lsmod command displays information about kernel modules currently loaded into the Linux kernel, listing each module’s name, size, usage count, and dependent modules.

Syntax

lsmod

Example

The output columns represent:

Column 1: module name

Column 2: module size

Column 3: number of dependent modules

Column 4: list of dependent modules

Typical usage includes filtering with lsmod | grep -i ext3 to check for specific modules.

2. lsof command

The lsof command lists open files, the processes that opened them, and associated network ports (TCP/UDP). It can also help recover deleted files and requires root privileges to access kernel memory.

Syntax

lsof(选项)

Options

-a: list processes with open files

-c<process_name>: list files opened by the specified process

-g: display GID details

-d<file_descriptor>: show processes using the given file descriptor

+d<directory>: list files opened under the directory

+D<directory>: recursively list files opened under the directory

-n: list NFS files

-i<criteria>: filter processes by protocol, port, or IP

-p<pid>: list files opened by the specified PID

-u: display UID details

-h: show help

-v: show version

Example

Key columns include COMMAND (process name), PID, PPID, USER, PGID, and FD (file descriptor).

3. lspci command

The lspci command lists all PCI bus devices and their details on the host.

Syntax

lspci(选项)

Options

-n: display numeric vendor and device codes

-t: show devices in a tree hierarchy

-b: bus-centric view

-d: filter by specific vendor/device

-s: show devices on a given bus/slot

-i: use a custom PCI ID list file

-m: machine‑readable output

Example

4. lsscsi command

The lsscsi command displays information about SCSI devices attached to the system.

Parameters

-s: show capacity size

-c: display full information

-d: show major/minor device numbers

-g: show corresponding sg device name

-H: list host controllers (options -Hl, -Hlv)

-l: display related attributes (options -ll, -lll, -L)

-v: show device attribute directories

-x: display LUN in hexadecimal

-p: output DIF/DIX protection types

-P: output valid protection mode information

-i: show udev‑related attributes

-w: display WWN

Example