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I am installing hadoop on my Ubuntu system. When I start it, it reports that port 9000 is busy.

I used:

netstat -nlp|grep 9000

to see if such a port exists and I got this:

   tcp        0      0 127.0.0.1:9000          0.0.0.0:*               LISTEN

But how can I get the PID of the process which is holding it?

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643

Your existing command doesn't work because Linux requires you to either be root or the owner of the process to get the information you desire.

On modern systems, ss is the appropriate tool to use to get this information:

$ sudo ss -lptn 'sport = :80'
State   Local Address:Port  Peer Address:Port              
LISTEN  127.0.0.1:80        *:*                users:(("nginx",pid=125004,fd=12))
LISTEN  ::1:80              :::*               users:(("nginx",pid=125004,fd=11))

You can also use the same invocation you're currently using, but you must first elevate with sudo:

$ sudo netstat -nlp | grep :80
tcp  0  0  0.0.0.0:80  0.0.0.0:*  LISTEN  125004/nginx

You can also use lsof:

$ sudo lsof -n -i :80 | grep LISTEN
nginx   125004 nginx    3u  IPv4   6645      0t0  TCP 0.0.0.0:80 (LISTEN)
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    Note: under OSX, the -p option is for protocol rather than process. See this question – Bryan P Apr 10 '16 at 16:51
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    @BryanP the OP asked for Ubuntu so that's kinda irrelevant... – Adam B Sep 21 '16 at 14:26
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    @AdamB Unless a Mac user arrived here searching for Finding the PID of the process using a specific port – mraaroncruz Oct 10 '16 at 11:05
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    This answer would probably be improved by putting the need to sudo at the top. – Nacht Jan 6 '17 at 1:10
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    @MrOnyancha Use the terse (-t) options - lsof -ti tcp:80 – Mohnish Jul 19 '17 at 13:58
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Also you can use lsof utility. Need to be root.

# lsof -i :25
COMMAND  PID        USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
exim4   2799 Debian-exim    3u  IPv4   6645      0t0  TCP localhost:smtp (LISTEN)
exim4   2799 Debian-exim    4u  IPv6   6646      0t0  TCP localhost:smtp (LISTEN)
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    This command will also give you processes with established connections, not just processes that are listening. – firelynx Aug 18 '15 at 10:10
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    Not necessarily to be root. And, for those who want to get PID only, you can lsof -i :25 -Fp, which produces output like p1234. – Robert Mar 9 '17 at 10:27
  • Important to note that you may need to run as sudo as some processes may be inaccessible to the user. – Harley Lang Mar 25 at 1:18
  • For more information on lsof: tecmint.com/10-lsof-command-examples-in-linux – Genius Apr 26 at 12:43
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I am using "CentOS 7 minimal" which has nor netstat neither lsof. But a lot of linux distributions have the socket statistics command (i.e. ss).

Here is an example of execution:

# ss -tanp | grep 6379
LISTEN   0    128  127.0.0.1:6379   *:*   users:(("redis-server",pid=2531,fd=4))
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Running the command with sudo would give you the PID. On my development machine I get:

$ netstat -nlp | grep 8080
tcp6       0      0 :::8080      :::*       LISTEN      -

$ sudo netstat -nlp | grep 8080
tcp6       0      0 :::8080      :::*       LISTEN      16449/java

And as mentioned in other answers you can also use the ss or the lsof commands.

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  • running command as sudo display process ID – Eugen Konkov May 10 '18 at 8:10
  • But what if sudo netstat -nlp | grep 34157 still display - instead of PID? – Eugen Konkov May 10 '18 at 8:16
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Also you can use fuser:

fuser -v -n tcp 22

The output :

                     USER        PID ACCESS COMMAND
22/tcp:              root        598 F.... sshd
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  • It doesn't working fuser -v -n tcp 80, even I try with sudo – SuperKrish Dec 2 '16 at 5:42
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    Note: This requires sudo if the offending process was also started with sudo – laggingreflex Jan 21 '17 at 8:14
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    This is a good thing to remember generally. Commands in Linux generally won't give information on processes started by root/sudo unless the command is run with Sudo. This is true even when the command does not normally need sudo to run correctly. – njfife Jul 6 '17 at 21:15
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I'm working on a Yocto Linux system that has a limited set of available Linux tools. I managed to find the process of a running port using the following commands (where I find the process using port 1883):

root@root:~# netstat -lt
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       
tcp        0      0 0.0.0.0:hostmon         0.0.0.0:*               LISTEN      
tcp        0      0 localhost.localdomain:domain 0.0.0.0:*               LISTEN      
tcp        0      0 0.0.0.0:9080            0.0.0.0:*               LISTEN      
tcp        0      0 0.0.0.0:1883            0.0.0.0:*               LISTEN      
tcp        0      0 :::hostmon              :::*                    LISTEN      
tcp        0      0 localhost:domain        :::*                    LISTEN      
tcp        0      0 :::ssh                  :::*                    LISTEN      
tcp        0      0 :::1883                 :::*                    LISTEN      
root@root:~# fuser 1883/tcp
290 
root@root:~# ps | grep 290
  290 mosquitt 25508 S    /usr/sbin/mosquitto -c /etc/mosquitto/mosquitto.conf
12141 root      8444 S    grep 290

As we can see above, it's the program /usr/sbin/mosquitto that's using port 1883.

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