10+ “lsof” Command Usage Examples in Linux

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This tutorial explains Linux “lsof” command, options and its usage with examples.

lsof – list open files

Description :

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lsof is a command meaning “list open files”, which is used in many Unix-like systems to report a list of all open files and the processes that opened them.

Usage :

lsof [OPTIONS]

Options :

-u s
This option selects the listing of files for the user whose login names or user ID numbers are in the comma-separated set s – e.g., “abe”, or “548,root”. (There should be no spaces in the set.)
-a
The -a option may be used to AND the selections.
-c c
This option selects the listing of files for processes executing the command that begins with the characters of c. Multiple commands may be specified, using multiple -c options. They are joined in a single ORed set before participating in AND option selection.
+D D
This option causes lsof to search for all open instances of directory D and all the files and directories it contains to its complete depth. Symbolic links within directory D are ignored – i.e, not followed.
-i [i]
This option selects the listing of files any of whose Internet address matches the address specified in i. If no address is specified, this option selects the listing of all Internet and x.25 (HP-UX) network files.
If -i4 or -i6 is specified with no following address, only files of the indicated IP version, IPv4 or IPv6, are displayed.
-p s
This option selects the listing of files for the processes whose ID numbers are in the comma-separated set s – e.g., “123” or “123,456”. (There should be no spaces in the set.)
Multiple process ID numbers are joined in a single ORed set before participating in AND option selection.
+|-r [t]
This option puts lsof in repeat mode. There lsof lists open files as selected by other options, delays t seconds (default fifteen), then repeats the listing, delaying and listing repetitively until stopped by a condition defined by the prefix to the option.
If the prefix is a `-‘, repeat mode is endless. Lsof must be terminated with an interrupt or quit signal.
If the prefix is `+’, repeat mode will end the first cycle no open files are listed – and of course when lsof is stopped with an interrupt or quit signal. When repeat mode ends because no files are listed, the process exit code will be zero if any open files were ever listed; one, if none were ever listed.

Examples :

1. List all Open Files with lsof Command

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# lsof
 
COMMAND    PID      USER   FD      TYPE     DEVICE  SIZE/OFF       NODE NAME
init         1      root  cwd      DIR      253,0      4096          2 /
init         1      root  rtd      DIR      253,0      4096          2 /
init         1      root  txt      REG      253,0    145180     147164 /sbin/init
init         1      root  mem      REG      253,0   1889704     190149 /lib/libc-2.12.so
init         1      root   0u      CHR        1,3       0t0       3764 /dev/null
init         1      root   1u      CHR        1,3       0t0       3764 /dev/null
init         1      root   2u      CHR        1,3       0t0       3764 /dev/null
init         1      root   3r     FIFO        0,8       0t0       8449 pipe
init         1      root   4w     FIFO       0,8       0t0       8449 pipe
init         1      root   5r      DIR       0,10         0          1 inotify
init         1      root   6r      DIR       0,10         0          1 inotify
init         1      root   7u     unix 0xc1513880       0t0       8450 socket

We’ll review FD & TYPE columns more precisely:

FD – stands for File descriptor and may seen some of the values as:
cwd current working directory
rtd root directory
txt program text (code and data)
mem memory-mapped file
Also in FD column numbers like 1u is actual file descriptor and followed by u,r,w of it’s mode as:
r for read access.
w for write access.
u for read and write access.

TYPE – of files and it’s identification.
DIR – Directory
REG – Regular file
CHR – Character special file.
FIFO – First In First Out

2. List User Specific Opened Files

The below command will display the list of all opened files of user abc.

# lsof -u abc
 
COMMAND  PID    USER   FD   TYPE     DEVICE SIZE/OFF   NODE NAME
sshd    1838 abc  cwd    DIR      253,0     4096      2 /
sshd    1838 abc  rtd    DIR      253,0     4096      2 /
sshd    1838 abc  txt    REG      253,0   532336 188129 /usr/sbin/sshd
sshd    1838 abc  mem    REG      253,0    19784 190237 /lib/libdl-2.12.so
sshd    1838 abc  mem    REG      253,0   122436 190247 /lib/libselinux.so.1
sshd    1838 abc  mem    REG      253,0   255968 190256 /lib/libgssapi_krb5.so.2.2
sshd    1838 abc  mem    REG      253,0   874580 190255 /lib/libkrb5.so.3.3

3. Find Processes running on Specific Port

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To find out all the running process of specific port, just use the following command with option -i. The below example will list all running process of port 22.

# lsof -i TCP:22
 
COMMAND  PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
sshd    1471    root    3u  IPv4  12683      0t0  TCP *:ssh (LISTEN)
sshd    1471    root    4u  IPv6  12685      0t0  TCP *:ssh (LISTEN)

4. List Only IPv4 & IPv6 Open Files

In below example shows only IPv4 and IPv6 network files open with separate commands.

# lsof -i 4
 
COMMAND    PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind   1203     rpc    6u  IPv4  11326      0t0  UDP *:sunrpc
rpcbind   1203     rpc    7u  IPv4  11330      0t0  UDP *:954
rpcbind   1203     rpc    8u  IPv4  11331      0t0  TCP *:sunrpc (LISTEN)
avahi-dae 1241   avahi   13u  IPv4  11579      0t0  UDP *:mdns
avahi-dae 1241   avahi   14u  IPv4  11580      0t0  UDP *:58600
 
# lsof -i 6
 
COMMAND    PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind   1203     rpc    9u  IPv6  11333      0t0  UDP *:sunrpc
rpcbind   1203     rpc   10u  IPv6  11335      0t0  UDP *:954
rpcbind   1203     rpc   11u  IPv6  11336      0t0  TCP *:sunrpc (LISTEN)
rpc.statd 1277 rpcuser   10u  IPv6  11858      0t0  UDP *:55800
rpc.statd 1277 rpcuser   11u  IPv6  11862      0t0  TCP *:56428 (LISTEN)
cupsd     1346    root    6u  IPv6  12112      0t0  TCP localhost:ipp (LISTEN)

5. List Open Files of TCP Port ranges 1-1024

To list all the running process of open files of TCP Port ranges from 1-1024.

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# lsof -i TCP:1-1024
 
COMMAND  PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind 1203     rpc   11u  IPv6  11336      0t0  TCP *:sunrpc (LISTEN)
cupsd   1346    root    7u  IPv4  12113      0t0  TCP localhost:ipp (LISTEN)
sshd    1471    root    4u  IPv6  12685      0t0  TCP *:ssh (LISTEN)
master  1551    root   13u  IPv6  12898      0t0  TCP localhost:smtp (LISTEN)
sshd    1834    root    3r  IPv4  15101      0t0  TCP 192.168.0.2:ssh->192.168.0.1:conclave-cpp (ESTABLISHED)
sshd    1838 tecmint    3u  IPv4  15101      0t0  TCP 192.168.0.2:ssh->192.168.0.1:conclave-cpp (ESTABLISHED)
sshd    1871    root    3r  IPv4  15842      0t0  TCP 192.168.0.2:ssh->192.168.0.1:groove (ESTABLISHED)
httpd   1918    root    5u  IPv6  15991      0t0  TCP *:http (LISTEN)
httpd   1918    root    7u  IPv6  15995      0t0  TCP *:https (LISTEN)

6. Exclude User with ‘^’ Character

Here, we have excluded root user. You can exclude a particular user using ‘^’ with command as shown above.

# lsof -i -u^root
 
COMMAND    PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind   1203     rpc    6u  IPv4  11326      0t0  UDP *:sunrpc
rpcbind   1203     rpc    7u  IPv4  11330      0t0  UDP *:954
rpcbind   1203     rpc    8u  IPv4  11331      0t0  TCP *:sunrpc (LISTEN)
rpcbind   1203     rpc    9u  IPv6  11333      0t0  UDP *:sunrpc
rpcbind   1203     rpc   10u  IPv6  11335      0t0  UDP *:954
rpcbind   1203     rpc   11u  IPv6  11336      0t0  TCP *:sunrpc (LISTEN)
avahi-dae 1241   avahi   13u  IPv4  11579      0t0  UDP *:mdns
avahi-dae 1241   avahi   14u  IPv4  11580      0t0  UDP *:58600
rpc.statd 1277 rpcuser    5r  IPv4  11836      0t0  UDP *:soap-beep
rpc.statd 1277 rpcuser    8u  IPv4  11850      0t0  UDP *:55146
rpc.statd 1277 rpcuser    9u  IPv4  11854      0t0  TCP *:32981 (LISTEN)
rpc.statd 1277 rpcuser   10u  IPv6  11858      0t0  UDP *:55800
rpc.statd 1277 rpcuser   11u  IPv6  11862      0t0  TCP *:56428 (LISTEN)

7. Find Out who’s Looking What Files and Commands?

Below example shows user abc is using command like ping and /etc directory .

# lsof -i -u abc
 
COMMAND  PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
bash    1839 abc  cwd    DIR  253,0    12288   15 /etc
ping    2525 abc  cwd    DIR  253,0    12288   15 /etc

8. List all Network Connections

The following command with option ‘-i’ shows the list of all network connections ‘LISTENING & ESTABLISHED’.

# lsof -i
 
COMMAND    PID    USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
rpcbind   1203     rpc    6u  IPv4  11326      0t0  UDP *:sunrpc
rpcbind   1203     rpc    7u  IPv4  11330      0t0  UDP *:954
rpcbind   1203     rpc   11u  IPv6  11336      0t0  TCP *:sunrpc (LISTEN)
avahi-dae 1241   avahi   13u  IPv4  11579      0t0  UDP *:mdns
avahi-dae 1241   avahi   14u  IPv4  11580      0t0  UDP *:58600
rpc.statd 1277 rpcuser   11u  IPv6  11862      0t0  TCP *:56428 (LISTEN)
cupsd     1346    root    6u  IPv6  12112      0t0  TCP localhost:ipp (LISTEN)
cupsd     1346    root    7u  IPv4  12113      0t0  TCP localhost:ipp (LISTEN)
sshd      1471    root    3u  IPv4  12683      0t0  TCP *:ssh (LISTEN)
master    1551    root   12u  IPv4  12896      0t0  TCP localhost:smtp (LISTEN)
master    1551    root   13u  IPv6  12898      0t0  TCP localhost:smtp (LISTEN)
sshd      1834    root    3r  IPv4  15101      0t0  TCP 192.168.0.2:ssh->192.168.0.1:conclave-cpp (ESTABLISHED)
httpd     1918    root    5u  IPv6  15991      0t0  TCP *:http (LISTEN)
httpd     1918    root    7u  IPv6  15995      0t0  TCP *:https (LISTEN)
clock-app 2362   narad   21u  IPv4  22591      0t0  TCP 192.168.0.2:45284->www.gov.com:http (CLOSE_WAIT)
chrome    2377   narad   61u  IPv4  25862      0t0  TCP 192.168.0.2:33358->maa03s04-in-f3.1e100.net:http (ESTABLISHED)
chrome    2377   narad   80u  IPv4  25866      0t0  TCP 192.168.0.2:36405->bom03s01-in-f15.1e100.net:http (ESTABLISHED)

9. Search by PID

The below example only shows whose PID is 1 [One].

# lsof -p 1
 
COMMAND PID USER   FD   TYPE     DEVICE SIZE/OFF   NODE NAME
init      1 root  cwd    DIR      253,0     4096      2 /
init      1 root  rtd    DIR      253,0     4096      2 /
init      1 root  txt    REG      253,0   145180 147164 /sbin/init
init      1 root  mem    REG      253,0  1889704 190149 /lib/libc-2.12.so
init      1 root  mem    REG      253,0   142472 189970 /lib/ld-2.12.so

10. List processes which opened a specific file

You can list only the processes which opened a specific file, by providing the filename as arguments.

# lsof /var/log/syslog
 
COMMAND  PID   USER   FD   TYPE DEVICE SIZE/OFF   NODE NAME
rsyslogd 488 syslog    1w   REG    8,1     1151 268940 /var/log/syslog

11. List opened files under a directory

You can list the processes which opened files under a specified directory using ‘+D’ option. +D will recurse the sub directories also. If you don’t want lsof to recurse, then use ‘+d’ option.

# lsof +D /var/log/
 
COMMAND   PID   USER  FD   TYPE DEVICE SIZE/OFF   NODE NAME
rsyslogd  488 syslog   1w   REG    8,1     1151 268940 /var/log/syslog
rsyslogd  488 syslog   2w   REG    8,1     2405 269616 /var/log/auth.log
console-k 144   root   9w   REG    8,1    10871 269369 /var/log/ConsoleKit/history

12. List opened files based on process names starting with

You can list the files opened by process names starting with a string, using ‘-c’ option. -c followed by the process name will list the files opened by the process starting with that processes name. You can give multiple -c switch on a single command line.

# lsof -c ssh -c init
 
COMMAND    PID   USER   FD   TYPE DEVICE SIZE/OFF   NODE NAME
init         1       root  txt    REG        8,1   124704  917562 /sbin/init
init         1       root  mem    REG        8,1  1434180 1442625 /lib/i386-linux-gnu/libc-2.13.so
init         1       root  mem    REG        8,1    30684 1442694 /lib/i386-linux-gnu/librt-2.13.so
...
ssh-agent 1528 abc           1u   CHR        1,3      0t0    4369 /dev/null
ssh-agent 1528 abc           2u   CHR        1,3      0t0    4369 /dev/null
ssh-agent 1528 abc           3u  unix 0xdf70e240      0t0   10464 /tmp/ssh-sUymKXxw1495/agent.1495

13. Kill all process that belongs to a particular user

When you want to kill all the processes which has files opened by a specific user, you can use ‘-t’ option to list output only the process id of the process, and pass it to kill as follows

# kill -9 `lsof -t -u abc1`

The above command will kill all process belonging to user ‘abc1’, which has files opened.

14. Execute lsof in repeat mode

lsof also support Repeat mode. It will first list files based on the given parameters, and delay for specified seconds and again list files based on the given parameters. It can be interrupted by a signal.

Repeat mode can be enabled by using ‘-r’ or ‘+r’. If ‘+r’ is used then, the repeat mode will end when no open files are found. ‘-r’ will continue to list,delay,list until a interrupt is given irrespective of files are opened or not.

Each cycle output will be separated by using ‘=======’. You also also specify the time delay as ‘-r’ | ‘+r’.

# lsof -u abc -c init -a -r5
 
=======
=======
COMMAND   PID USER   FD   TYPE DEVICE SIZE/OFF    NODE NAME
inita.sh 2971 abc  cwd    DIR    8,1     4096  393218 /home/abc
inita.sh 2971 abc  rtd    DIR    8,1     4096       2 /
inita.sh 2971 abc  txt    REG    8,1    83848  524315 /bin/dash
inita.sh 2971 abc  mem    REG    8,1  1434180 1442625 /lib/i386-linux-gnu/libc-2.13.so
inita.sh 2971 abc  mem    REG    8,1   117960 1442612 /lib/i386-linux-gnu/ld-2.13.so
inita.sh 2971 abc    0u   CHR  136,4      0t0       7 /dev/pts/4
inita.sh 2971 abc    1u   CHR  136,4      0t0       7 /dev/pts/4
inita.sh 2971 abc    2u   CHR  136,4      0t0       7 /dev/pts/4
inita.sh 2971 abc   10r   REG    8,1       20  393578 /home/abc/inita.sh
=======

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He is Linux Kernel Developer & SAN Architect and is passionate about competency developments in these areas. He lives in Bangalore and delivers focused training sessions to IT professionals in Linux Kernel, Linux Debugging, Linux Device Drivers, Linux Networking, Linux Storage, Advanced C Programming, SAN Storage Technologies, SCSI Internals & Storage Protocols such as iSCSI & Fiber Channel. Stay connected with him @ LinkedIn