ulimit confusion.

Hi.
I've been playing around with ulimit and I have some questions.
If I raise a limit with $ ulimit -n 10000 is this hard or soft?
If I raise a limit with $ ulimit -n 1025 it works, then I try to lower the limit back to its default 1024 with $ ulimit -n 1024 I get an error. Why?
To edit the /etc/security.limits.conf is it safe to use vim/nano?
Thanks.
Comments
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Hi @WarrenUK ,
If I raise a limit with $ ulimit -n 10000 is this hard or soft?
If you don't specify -H for hard or -S for soft, you are doing it for both. Look at this:
1.- Checking the hard limit:
[email protected]:~$ ulimit -Hn
5242882.- Checking the soft limit:
[email protected]:~$ ulimit -Sn
10243.- Modifying the limits:
[email protected]:~$ ulimit -n 10254.- Checking the limits again:
[email protected]:~$ ulimit -Hn
1025
[email protected]:~$ ulimit -Sn
1025If I raise a limit with $ ulimit -n 1025 it works, then I try to lower the
limit back to its default 1024 with $ ulimit -n 1024 I get an error. Why?1.- What's the exact error you are getting?
2.- What user is running the command?
3.- What distro and version are you running?To edit the /etc/security.limits.conf is it safe to use vim/nano?
While you put the right information in there, there will no harm.
Regards,
Luis.0 -
@luisviveropena said:
If I raise a limit with $ ulimit -n 1025 it works, then I try to lower the
limit back to its default 1024 with $ ulimit -n 1024 I get an error. Why?1.- What's the exact error you are getting?
2.- What user is running the command?
3.- What distro and version are you running?In a fresh terminal:
$ ulimit -n 1025 works ok
$ ulimit -n 1024 works ok
$ ulimit -n 1025 error
bash: ulimit: open files: cannot modify limit: Operation not permitted0 -
Hi @WarrenUK ,
Please provide the requested information, so I can try to help you.
1.- What user is running the command? Is it a normal user, is it root?
2.- What distro and version are you running?
3.- Check /etc/security/limits.conf for limits.
Regards,
Luis.0 -
- normal user
- Kubuntu 19.10
- Nothing is set in limits.conf
Here is my output for ulimit -a
core file size (blocks, -c) 0
data seg size (kbytes, -d) unlimited
scheduling priority (-e) 0
file size (blocks, -f) unlimited
pending signals (-i) 31181
max locked memory (kbytes, -l) 65536
max memory size (kbytes, -m) unlimited
open files (-n) 1024
pipe size (512 bytes, -p) 8
POSIX message queues (bytes, -q) 819200
real-time priority (-r) 0
stack size (kbytes, -s) 8192
cpu time (seconds, -t) unlimited
max user processes (-u) 31181
virtual memory (kbytes, -v) unlimited
file locks (-x) unlimitedI'm confused by what is a hard and soft limit in this output?
0 -
Hi.
I've had another play around. This is confusing me.
$ ulimit -H -n
1048576
$ ulimit -S -n
1024
$ ulimit soft
$ ulimit -n 10000
$ ulimit -H -n
100000I thought the soft limit could be set up and down up to the hard limit? I can set the soft limit upwards once and then progressively lower it down and down but I can never increase it again as the hard limit comes down with the soft limit even though I am not choosing the hard limit at the terminal.
0 -
Hi @WarrenUK ,
I thought the soft limit could be set up and down up to the hard limit?
That's correct.
I can set the soft limit upwards once and then progressively lower it down
and down but I can never increase it again as the hard limit comes down
with the soft limit even though I am not choosing the hard limit at the terminal.Nop, that happens because you are lowering down the hard limit, here:
$ ulimit -n 10000
When you don't specify if it's soft or hard, the ulimit command will affect both.
Regards,
Luis.0 -
Hi Luis.
So if I do
$ ulimit soft
$ ulimit -n 10000 <<<< this will set both hard and soft limit at the same time?What is the $ ulimit soft command for then?
Many thanks.
0 -
Hi Warren,
So if I do
>
$ ulimit soft
$ ulimit -n 10000 <<<< this will set both hard and soft limit at the same time?Yes, that's right.
What is the $ ulimit soft command for then?
If you want to rise the soft limit to 10000, you do the following:
ulimit -Sn 10000
Look at this:
[email protected]:~$ ulimit -Sn
1024
[email protected]:~$ ulimit -Hn
524288
[email protected]:~$ ulimit -Sn 10000
[email protected]:~$ ulimit -Sn
10000
[email protected]:~$ ulimit -Hn
524288
[email protected]:~$Regards,
Luis.0
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