Closing open file without killing the process

I have java(yeah java...) application running on CentOS 7. After a while, there are many "deleted" files that bother me.

for deleted files used(not the issue):

lsof | grep "(deleted)"

I found them in /proc/pid/fd/... and my question is how can I kill/delete them without killing the process(process have to run 24/7).

I saw on google that I can use gdb tool, but I don't know how to use it. Can you please help me(just to write step-by-step manual)?

I will love to hear some other suggestions if you have.

igor

Posted 2015-08-27T13:09:54.210

Reputation: 253

@user20574 If another program was writing to the file, and it lost the handle to it, it's obvious that would cause a file corruption. – Glimpse – 2018-07-27T00:05:07.567

@Glimpse well yes, but only to the file you force-closed. It's not obvious that it will also corrupt other files at random. – user253751 – 2018-07-27T02:14:57.997

I am more curious about how to NOT make this happen in the first place. That is to ask: how to delete files properly in Java so they don't end up appearing as "deleted" but "open" files that you need to "clean up" separately. – jyu – 2019-11-06T23:32:39.030

Answers

use lsof -p $PID and find the file descriptor (4th column)

root@blah:~# lsof -p 1737 | grep "(deleted)" apache2 1737 root 6w REG 0,25 0 207401 (deleted)/var/log/apache2/other_vhosts_access.log

4th column is 6w, meaning file descriptor 6 and it was opened for writing (w).

Then:

gdb -p $PID p close($FD)

eg:

gdb -p 1737 ..... (gdb) p close(6) $1 = 0 ... Quit anyway? (y or n) y Detaching from program: /usr/lib/apache2/mpm-prefork/apache2, process 1737

damolp

Posted 2015-08-27T13:09:54.210

Reputation: 266

THANKS, finally a good working simple answer!! btw, all my processes has 'x'u in 4th column. What does "u" means? – igor – 2015-08-30T06:28:22.763

u means that the file descriptor is opened reading and writing – damolp – 2015-08-31T01:34:18.153

Use the following command to find the deleted files file descriptors and you may truncate them afterwards

find /proc/ -mindepth 3 -maxdepth 3 \ -regex '/proc/[1-9][0-9]/fd/[1-9][0-9]' -type l -lname '*(deleted)' \ -printf '%p\n %l\n' 2>/dev/null

kashminder

Posted 2015-08-27T13:09:54.210

Reputation: 149