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This article introduces the knowledge of "how to solve the problem of opening too many files in Linux". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Answer 1.

[root@lxadmin nginx] # cat / proc/sys/fs/file-max

8192

Maximum number of files that can be opened in the file system

[root@lxadmin nginx] # ulimit-n

1024

The program is limited to 1024 files.

Use [root@lxadmin nginx] # ulimit-n 8192 to adjust

Or permanently adjust the number of open files can be added at the end of the startup file / etc/rc.d/rc.local (adding fs.file-max=xxx at the end of / etc/sysctl.conf is not valid)

Ulimit-n 8192

Answer 2.

The Linux kernel sometimes reports "Too many open files" because the file-max default value (8096) is too small. To solve this problem, you can execute the following commands as root (or add them to the init script under / etc/rcS.d/*. )

# echo "65536" > / proc/sys/fs/file-max # for version 2.2 and 2.4 kernels

# echo "131072" > / proc/sys/fs/inode-max # is only applicable to version 2.2 kernel

Answer 3.

The way to do this is to modify the operating system's limit on the number of open files as follows:

1. Set up the system according to the requirements for the maximum number of open files, and check the / proc/sys/fs/file-max file to make sure that the maximum number of open files has been set correctly.

# cat / proc/sys/fs/file-max

If the setting is too small, modify the variable in the file / etc/sysctl.conf to the appropriate value. This will take effect after each restart. If the setting is large enough, skip the next step.

# echo 2048 > / proc/sys/fs/file-max

Edit the file / etc/sysctl.conf and insert the following line.

Fs.file-max = 8192

two。 To set the maximum number of open files in the / etc/security/limits.conf file, here is a prompt:

#

Add the following line.

*-nofile 8192

This line sets the default number of open files per user to 2048. Note that there are two possible restrictions for the "nofile" item. Are hard and soft under this item. For the maximum number of open files to take effect, these two limits must be set. If you use the "-" character setting, the hard and soft settings are set at the same time.

The hard limit indicates the maximum value that can be set in the soft limit. The soft limit refers to the setting for which the current system is in effect. The hard limit can be lowered by ordinary users. But it cannot be increased. The soft limit cannot be higher than the hard limit. Only root users can increase the hard limit.

When adding a file limit description, you can simply double the current value. As an example, if you want to increase the default value of 1024, you'd better increase it to 2048, and if you want to continue to increase it, you need to set it to 4096.

Another situation is that there are two possibilities when creating an index. one is that the merge factor is too small, resulting in the number of files created exceeding the operating system limit, and the merge factor can be modified. You can also modify the operating system limit on the number of open files. The other is that the merging factor cannot be adjusted to a larger size due to the limitation of virtual machine memory, and the number of doc that needs to be indexed is very large, so it can only be solved by modifying the open file limit of the operating system.

On this basis, I also modified the following configuration file

Vi / etc/sysctl.conf

Add:

# Decrease the time default value for tcp_fin_timeout connection

Net.ipv4.tcp_fin_timeout = 30

# Decrease the time default value for tcp_keepalive_time connection

Net.ipv4.tcp_keepalive_time = 1800

# Turn off tcp_window_scaling

Net.ipv4.tcp_window_scaling = 0

# Turn off the tcp_sack

Net.ipv4.tcp_sack = 0

# Turn off tcp_timestamps

Net.ipv4.tcp_timestamps = 0

Then service network restart, these are all TCP sockets-related optimizations.

In addition, you need to add it to / etc/rc.d/rc.local to make it take effect when you restart.

Echo "30" > / proc/sys/net/ipv4/tcp_fin_timeout

Echo "1800" > / proc/sys/net/ipv4/tcp_keepalive_time

Echo "0" > / proc/sys/net/ipv4/tcp_window_scaling

Echo "0" > / proc/sys/net/ipv4/tcp_sack

Echo "0" > / proc/sys/net/ipv4/tcp_timestamps

Because not all programs run under root, all linux have a distinction between hard and soft open files. Ordinary users are limited by hard. No matter how high the value of ulimit-n $is, they cannot run to the value of nofile in / etc/security/limits.conf.

After this optimization, lsof-p $java_pid | wc-l can run to more than 4, 000 without throwing too many open files.

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