Linux handle restrictions

Linux handle restrictions
Linux handle restrictions

 

Linux handles can be divided into 1 system level limit and 2 user level limit:

/Proc/sys/fs/nr_open>/proc/sys/fs/file-max> = ulimit-Hn> = ulimit-Sn

1 system-level limit: 1.1/proc/sys/fs/nr_open

The maximum number of file handles supported by the System File System. The default value is 1048576 (1 M). The maximum value is limited by the system memory. This is the maximum value for all restrictions.

1.2/proc/sys/fs/file-max

The maximum number of file handles supported by the system file system must be smaller than nr_open. view the command (the following three commands are equivalent ):

[root@vm-cdh4 ~]# sysctl -a | grep -i file-max --colorfs.file-max = 188436[root@vm-cdh4 ~]# cat /proc/sys/fs/file-max188436[root@vm-cdh4 ~]# sysctl -e fs.file-maxfs.file-max = 188436

Run the following command to view the number of opened file descriptors used by the current system:

 

[root@vm-cdh4 ~]# cat /proc/sys/fs/file-nr832    0    188436

File-max = 188436

 

1.3 change file-max

Temporary changes, disappears after restart:

 

[root@vm-cdh4 ~]# sysctl -w fs.file-max=102400

Permanent changes, In /Etc/sysctl. conf(Applicable to kernels 2.2 and 2.4 ):

 

 

Fs. file-max = 102400 #### only for the 2.2 kernel: #### fs. inode-max = 102400

When /Etc/sysctl. confAfter the change, run the following command to make the change take effect immediately:

[root@vm-cdh4 ~]# sysctl -p

 

2. user-level limit: 2.1 hard upper limit: ulimit-Hn

The maximum number of handles of a single process. <= file-max. view the command:

 

[root@vm-cdh4 ~]# ulimit -Hn4096

Temporary changes, Disappears after restart:

 

 

[root@vm-cdh4 ~]# ulimit -Hn 8192[root@vm-cdh4 ~]# ulimit -Hn8192

 

2.2 Soft Upper Limit ulimit-Sn

The maximum number of handles for a single process. <= ulimit-Hn. view the command:

 

[root@vm-cdh4 ~]# ulimit -Sn1024[root@vm-cdh4 ~]# ulimit -n1024

Temporary changes, Disappears after restart:

 

 

[root@vm-cdh4 ~]# ulimit -Sn 8000[root@vm-cdh4 ~]# ulimit -n8000

 

2.3 modify the maximum number of handles of a single process

Modify the soft and hardware limits temporarily (<= file-max)Disappears after restart:

 

[root@vm-cdh4 ~]# ulimit-SHn 10240

 

Permanently modify the hard and soft limits (RHEL6.4 )./Etc/security/limits. conf(* Indicates all users ):

 

#......#@student        -       maxlogins       4*    hard    nofile    10240*    soft    nofile    10240# End of file