How to Increase Ulimit Values in Linux easily

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How to Increase Ulimit Values in Linux easily

We can set up two limits as shown in the below image.

Here we are going to see how to set the soft limit and hard limit to the users and also we will see how to increase the system limit.

1. Check the user shell’s soft limit ? Here my user is user1.

[[email protected] ~]$ ulimit -Sa
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 11949
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 8192
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) 10240
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4096
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
[[email protected] ~]$

2. Check the user shell’s hard limit ? Here is the user is user1.

[[email protected] ~]$ ulimit -Ha
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 11949
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 8192
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) unlimited
cpu time               (seconds, -t) unlimited
max user processes              (-u) 4096
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
[[email protected] ~]$

3. User can set their own soft limit ?

Yes. They can able to set their own soft limit up to the hard limit value. Hard limit’s are managed by root user. You can reduce the hardlimit but you can;t increase being a normal user.

You will get the below error, If you try to increase the hard limit from normal user.

[[email protected] ~]$ ulimit -H -u 12288
-bash: ulimit: max user processes: cannot modify limit: Operation not permitted

4.How to increase the hard and soft limit value for user from root login?

To increase the soft & hard limit values to the users, we need to edit “/etc/security/limits.conf” file. Here is the user1’s user’s configuration in limits.conf.

[[email protected] ~]$ tail -7 /etc/security/limits.conf
# End of file
user1   soft   nofile    8192
user1   hard   nofile    8192
user1   soft   nproc    4096
user1   hard   nproc    8192
user1   soft   core    unlimited
user1   hard   core    unlimited
[[email protected] ~]$

After modifying the file, user need to logoff and login again to see the new values.

5.limits.conf file will be used to set the user level limit.Where to set the system level limits ?

To set the system-wide limit, you need to edit the “/etc/sysctl.conf”.For an example, if you want to set number of open files system-wide, edit sysctl.conf and re-load the configuration. Existing system-wide open files limit,

[[email protected] ~]# cat /proc/sys/fs/file-max
6815744
[[email protected] ~]#

Edit the open files value in  sysctl.conf like below,

[[email protected] ~]# cat /etc/sysctl.conf |grep file-max
fs.file-max = 6816768
[[email protected] ~]#

Re-load the configuration,and check the system-wide open files value

[[email protected] ~]# sysctl -p
net.ipv4.ip_forward = 0
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
error: “net.bridge.bridge-nf-call-ip6tables” is an unknown key
error: “net.bridge.bridge-nf-call-iptables” is an unknown key
error: “net.bridge.bridge-nf-call-arptables” is an unknown key
kernel.sem = 250 32000 100 128
kernel.shmmax = 4294967295
fs.file-max = 6816768
[[email protected] ~]# cat /proc/sys/fs/file-max
6816768
[[email protected] ~]#

We have successfully changed the system-wide open files (File descriptor) value.
You can also simply execute the single command to modify these value,but that change will not persist across the system reboot.

[[email protected] ~]# sysctl -w fs.file-max=6816768
fs.file-max = 6816768
[[email protected] ~]# cat /proc/sys/fs/file-max
6816768
[[email protected] ~]#

Hope now you are clear with modifying the ulimit values for user and setting the new resource limit in sysctl.conf file.

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