linux setting ulimit -n over 1 million [closed] - linux

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I'm building an system where I have 1 million open connections open at the same time and some of them reconnect but the thread still waits the deadline.
ulimit -n 999999 is the maximum I can get everything over it will give an error message
-bash: ulimit: open files: cannot modify limit: Operation not permitted
How can I set this higher? Why is there even an limit?

Start by settting this in sysctl:
# sysctl -w fs.nr_open=1000000000
Then you can set the ulimit
# ulimit -n 1000000000
This will give you 1000000000 as your ulimit:
# ulimit -n
1000000000
1000000000 is the highest I could get it to go.

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how to check I/O utilization of a process in Linux using commands [closed]

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Closed 5 years ago.
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I want to know the i/o utilization of every process using commands.
like this,
enter image description here
You can monitor disk I/O for processes with
iotop
htop
btrace
Also you can get the I/O per process using /proc/<PID>/io:
[home ~]# cat /proc/24328/io
rchar: 5532416
wchar: 67578
syscr: 6548
syscw: 249
read_bytes: 0
write_bytes: 20480
cancelled_write_bytes: 0

Increase /tmp directory space in linux 7 through terminal [closed]

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Closed 6 years ago.
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I have problem in installing oracle DB since /tmp has no required freespace. How to increase the space of /tmp folder from terminal?
hope you have some free space in the disk. Its possible to make free space to a particular partition here its /tmp
Open the terminal and run
df -h
this will show the disk space currently you have in the system
to increase the space for the partition
type
`sudo umount /tmp`
sudo mount -t tmpfs -o size=1048576,mode=1777 overflow /tmp
this will increase the size by 1MB if you add and extra zero that is 10485760 will increase the size by 10MB. Add space upon how much you needed.

Limit packets per minute per IP address [closed]

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Only using IPTABLES, how would you limit requests (pings for example) from the same Internet host to x number of packets per minute, say 5 for simplicity sake?
iptables -A INPUT -p ICMP -m limit --limit 5/minute --limit-burst 5 -j ACCEPT
-m limit: This uses the limit iptables extension
–limit 5/minute: This limits only maximum of 5 connection per minute. Change this value based on your specific requirement
–limit-burst 5: This value indicates that the limit/minute will be enforced only after the total number of connection have reached the limit-burst level.
The above should do the trick!

How to change maximum no of file descriptors open in linux? [closed]

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Closed 9 years ago.
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When i try to open max number of simultaneous socket connection using epoll , it stucks on 1024 .After this it give "Too many files open" error . I know that this is not the limit .I tried to change nofile parameter value in /etc/security/limits.conf but i only have read-only permissions there.Is there any method to increase the number of file descriptors opened simultaneously?
The answer is in the documentation for ulimit which governs this an other limits.
See e.g. Why is the number of open files limited in linux
This gives you an answer, you can try setting ulimit -n.

How to fetch cpu utilization of a particular process in linux [closed]

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I have used following command to fetch the CPU utilization of a process. It is giving result, but it is not coming out. I have used following command.
top | grep <processname>
I just want to put this in a loop and I will insert sleep in the code so that I can fetch the value in regular intervals
Use top's batch mode, eg.
top -b -n1 | grep processname
You can do:
while [ 1 ]; do top -n 1 | grep something; sleep 1; done
Use the -n option of top:
-n
Number of iterations. Update the display this number of times and then exit.

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