如何找出linux进程的打开文件描述？

Question

在运行我的go程序时，我在日志中发现了很多错误，例如“打开的文件太多”，我只是想找出哪个进程用完了fds，然后我运行了这个命令：

lsof -n |awk '{print $2}'|sort|uniq -c |sort -nr

返回结果如

279605 20341 62748 19861 10310 19712 5434 21318 3484 27344 2842 19781 2400 20372 2346 24153 2123 5214 1540 21123

pid 为 20341 的进程是 mongod 进程，对此我感到很惊讶。所以我尝试了另一种方式：

lsof -p 20341 | wc -l

但让我烦恼的是它的结果是：567。

然后，我尝试另一种方式：ll /proc/20341/fd | wc -l 结果是 496。

我现在很困惑，哪个是对的，它们之间有什么不同？

谢谢。

---

更新于：2018-05-31 10:35:33

• 获取 mongodb PID [root@node26 10:34:54 ~]$ps aux | grep mongo mongodb 20341 2.4 1.9 25419812 1257420 ? Sl May28 107:58 /usr/bin/mongod --quiet -f /etc/mongod.conf run

• 命令lsof -p [root@node26 10:36:12 ~]$lsof -p 20341 | wc -l 570

• 目录 [root@node26 10:36:33 ~]$ll /proc/20341/fd/ | wc -l 499

• 命令lsof + grep [root@node26 10:37:33 ~]$lsof | grep 20341 | wc -l 282223

  • 前10 mongod 20341 mongodb cwd DIR 9,127 4096 2 / mongod 20341 mongodb rtd DIR 9,127 4096 2 / mongod 20341 mongodb txt REG 9,127 12238320 2499177 /usr/bin/mongod mongod 20341 mongodb mem REG 9,127 67108864 1969114 /var/lib/mongodb/a_dev.0 mongod 20341 mongodb mem REG 9,127 536870912 1968852 /var/lib/mongodb/a_dev.ns mongod 20341 mongodb mem REG 9,127 67108864 1968447 /var/lib/mongodb/a.0 mongod 20341 mongodb mem REG 9,127 536870912 1968347 /var/lib/mongodb/a.ns mongod 20341 mongodb mem REG 9,127 67108864 1968453 /var/lib/mongodb/b.0 mongod 20341 mongodb mem REG 9,127 536870912 1968449 /var/lib/mongodb/b.ns mongod 20341 mongodb mem REG 9,127 67108864 1968590 /var/lib/mongodb/c.0
  • 中间10 mongod 20341 27018 mongodb 490u IPv4 143223380 0t0 TCP node26:27017->node24:59172 (ESTABLISHED) mongod 20341 27018 mongodb 491u IPv4 143758325 0t0 TCP node26:27017->node25:43016 (ESTABLISHED) mongod 20341 27018 mongodb 492u IPv4 143762443 0t0 TCP node26:27017->node24:60602 (ESTABLISHED) mongod 20341 27018 mongodb 493u IPv4 154865226 0t0 TCP node26:27017->node26:54800 (ESTABLISHED) mongod 20341 27018 mongodb 494u IPv4 164046515 0t0 TCP node26:27017->node24:42952 (ESTABLISHED) mongod 20341 27018 mongodb 495u IPv4 164046516 0t0 TCP node26:27017->node24:42960 (ESTABLISHED) mongod 20341 27018 mongodb 497u IPv4 154865844 0t0 TCP node26:27017->node25:41976 (ESTABLISHED) mongod 20341 27018 mongodb 500u IPv4 164046517 0t0 TCP node26:27017->node24:42968 (ESTABLISHED) mongod 20341 27018 mongodb 502u IPv4 164046518 0t0 TCP node26:27017->node26:60306 (ESTABLISHED) mongod 20341 27018 mongodb 503u IPv4 164046519 0t0 TCP node26:27017->node26:60314 (ESTABLISHED)
  • 尾10 mongod 20341 32608 mongodb 492u IPv4 143762443 0t0 TCP node26:27017->node24:60602 (ESTABLISHED) mongod 20341 32608 mongodb 493u IPv4 154865226 0t0 TCP node26:27017->node26:54800 (ESTABLISHED) mongod 20341 32608 mongodb 494u IPv4 164046515 0t0 TCP node26:27017->node24:42952 (ESTABLISHED) mongod 20341 32608 mongodb 495u IPv4 164046516 0t0 TCP node26:27017->node24:42960 (ESTABLISHED) mongod 20341 32608 mongodb 497u IPv4 154865844 0t0 TCP node26:27017->node25:41976 (ESTABLISHED) mongod 20341 32608 mongodb 500u IPv4 164046517 0t0 TCP node26:27017->node24:42968 (ESTABLISHED) mongod 20341 32608 mongodb 502u IPv4 164046518 0t0 TCP node26:27017->node26:60306 (ESTABLISHED) mongod 20341 32608 mongodb 503u IPv4 164046519 0t0 TCP node26:27017->node26:60314 (ESTABLISHED) mongod 20341 32608 mongodb 505u IPv4 164046523 0t0 TCP node26:27017->node26:60322 (ESTABLISHED) mongod 20341 32608 mongodb 730u IPv4 117137926 0t0 TCP node26:27017->node25:54730 (ESTABLISHED)

Answer 1

/proc/${pid}/fd 包含连接到 shell 的文件描述符，在 lsof 中显示为一个数字，后跟一个 u：

$ la /proc/$$/fd
total 0
lrwx------ 1 username users 64 May 30 20:08 0 -> /dev/pts/0
lrwx------ 1 username users 64 May 30 20:08 1 -> /dev/pts/0
lrwx------ 1 username users 64 May 30 20:08 2 -> /dev/pts/0
lrwx------ 1 username users 64 May 30 20:08 255 -> /dev/pts/0
$ lsof -p $$
COMMAND  PID     USER   FD   TYPE DEVICE SIZE/OFF    NODE NAME
bash    3720 username  cwd    DIR  254,3    12288 1835009 /home/username
bash    3720 username  rtd    DIR  254,2     4096       2 /
bash    3720 username  txt    REG  254,2   859688 2890163 /usr/bin/bash
bash    3720 username  mem    REG  254,2    46912 2885785 /usr/lib/libnss_files-2.27.so
bash    3720 username  mem    REG  254,2  2942480 2930144 /usr/lib/locale/locale-archive
bash    3720 username  mem    REG  254,2   457800 2890072 /usr/lib/libncursesw.so.6.1
bash    3720 username  mem    REG  254,2  2105608 2885835 /usr/lib/libc-2.27.so
bash    3720 username  mem    REG  254,2    14144 2885777 /usr/lib/libdl-2.27.so
bash    3720 username  mem    REG  254,2   363064 2890132 /usr/lib/libreadline.so.7.0
bash    3720 username  mem    REG  254,2   177680 2885836 /usr/lib/ld-2.27.so
bash    3720 username    0u   CHR  136,0      0t0       3 /dev/pts/0
bash    3720 username    1u   CHR  136,0      0t0       3 /dev/pts/0
bash    3720 username    2u   CHR  136,0      0t0       3 /dev/pts/0
bash    3720 username  255u   CHR  136,0      0t0       3 /dev/pts/0

它们都是“正确的”，但来自lsof 的计数与用完打开文件有关。

要查找相关的打开文件限制，请使用ulimit -n。