Archive for the tag 'sockets'

SB-Shibu
Jan 21st, 2010

fuser - identify processes using files or sockets

fuser - identify processes using files or sockets

In order to look up processes using TCP and UDP sockets, the corresponding name space has to be selected with the -n option. By default fuser will look in both IPv6 and IPv4 sock-ets. To change the default, behavior, use the -4 and -6 options. The socket(s) can be specified by the local and remote port, and the remote address. All fields are optional, but commas in front of missing fields must be present:

[lcl_port][,[rmt_host][,[rmt_port]]]

Either symbolic or numeric values can be used for IP addresses and port numbers.

fuser outputs only the PIDs to stdout, everything else is sent to stderr.

root@dell:~# fuser -nv tcp 25
USER PID ACCESS COMMAND
25/tcp: root 3926 F…. master

FILES

/proc location of the proc file system

EXAMPLES

fuser -km /home kills all processes accessing the file system /home in any way.

if fuser -s /dev/ttyS1; then :; else something; fi invokes something if no other process
is using /dev/ttyS1.

fuser telnet/tcp shows all processes at the (local) TELNET port.

SB-Shibu
Jul 28th, 2009

see all tcp sockets currently open

In order to see all TCP sockets currently open, run (as root).

# lsof -i TCP

If all of the sockets in question on your webserver port (port 80), you should be able to list only those with

# lsof -i TCP:80

lsof is another tool for locating open files. lsof (no options) will list all files opened by any processes currently running. To restrict this to processes owned by username, use

lsof -u username.