Linux ulimit command details how to use Linux ulimit command

Ulimit is a shell-built directive that can be used to control the resources of shell execution programs.

Grammar

ulimit [-ahs][-c <core file Caps >][-d < data section size >][-f < file size >][-m < memory size]

[-N < number of files] [-p < buffer size] [-s < stacking size] [t <cpu time] [-U < Program number] [-v < virtual memory size]

Parameters:

• -a displays the current resource constraint settings.
• -c <core File upper limit > set the maximum value of core file, the unit is block.
• -D < data section size > The maximum value of the data section of the program, in kilobytes.
• -F < file size > The largest file the shell can establish, in blocks.
• -H set the hard limit of the resource, which is the limit set by the administrator.
• -m < memory size > Specifies the maximum amount of memory that can be used, in kilobytes.
• -N < number of files > Specify the maximum number of files that can be opened at the same time.
• -p < buffer size > Specifies the size of the pipe buffer, in units of 512 bytes.
• -s < stacking size > Specifies the upper bound of the stack in kilobytes.
• -S sets the flexibility limit for resources.
• -T <CPU time > Specify the maximum CPU usage time in seconds.
• -U < number of programs > The maximum number of programs that users can open.
• -v < virtual memory size > Specify the maximum amount of virtual memory that can be used, in kilobytes.

Instance

To display system resource settings

[Root@w3cschool.cc ~]# Ulimit-a

Core file size (blocks,-c) 0

Data seg Size (Kbytes,-D) Unlimited

File size (blocks,-f) Unlimited

Pending Signals (I.) 1024

Max locked Memory (Kbytes, L) 32

Max memory Size (Kbytes, M) Unlimited

Open files (-N) 1024

Pipe Size (bytes, p) 8

POSIX message queues (bytes,-Q) 819200

Stack size (Kbytes,-s) 10240

CPU time (seconds,-t) unlimited

MAX User Processes (-u) 4096

Virtual Memory (Kbytes,-V) Unlimited

File locks (-X) Unlimited

[Root@w3cschool.cc ~]#

Set the maximum number of single user programs

[root@w3cschool.cc ~]# ulimit-u 500//Set a single user program limit

[Root@w3cschool.cc ~]# Ulimit-a

Core file size (blocks,-c) 0

Data seg Size (Kbytes,-D) Unlimited

File size (blocks,-f) Unlimited

Pending Signals (I.) 1024

Max locked Memory (Kbytes, L) 32

Max memory Size (Kbytes, M) Unlimited

Open files (-N) 1024

Pipe Size (bytes, p) 8

POSIX message queues (bytes,-Q) 819200

Stack size (Kbytes,-s) 10240

CPU time (seconds,-t) unlimited

MAX User Processes (-u) 500

Virtual Memory (Kbytes,-V) Unlimited

File locks (-X) Unlimited

[Root@w3cschool.cc ~]#