How to change max open files for nginx server on Ubuntu

The following error occurred a lot in /var/log/nginx/error.log:

Too many open files

This means that the nginx master process reached the maximum number of open files which was set to the default of 4096. (To check it, simply cat /proc/pid/limits, where pid is the process id)

To resolve, this, edit /lib/systemd/system/nginx.service and add the following line:

LimitNOFILE=30000 #change it according to your needs

Then reload the systemctl daemon:

sudo systemctl daemon-reload

and finally restart the nginx service:

sudo service nginx restart

That’s it, the error is gone!

Tested on Ubuntu 16.04 with nginx 1.17, should work with any other OS using systemd.

Enjoy!

Sources:

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Add a new HDD to a VM without rebooting on Ubuntu server

Firstly, install scsitools package:

sudo apt install scsitools

Then run the command rescan-scsi-bus:

sudo rescan-scsi-bus

That’s it, your new virtual HDD has now been detected.

Another way would be to do it with a loop and without the need for that package:

for host in ls /sys/class/scsi_host/; do
echo "- - -" > /sys/class/scsi_host/${host}/scan;
done

Enjoy!

Sources:

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A cute little screenshot and annotation tool on Linux

A very handy screenshot tool that works very well on my KDE plasma desktop on Ubuntu 19.10 is ksnip, which you can get from here: https://github.com/damirporobic/ksnip

Just download and install the deb file and that’s it!

Enjoy!

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Restart network manager indicator in KDE Plasma Desktop

sudo service NetworkManager restart

Note: This is specifically for the network icon in the system tray and is different from the network-manager service which controls the whole Linux network manager:

Tested on Ubuntu 19.10 with KDE Plasma 5.16.5

Source: https://bbs.archlinux.org/viewtopic.php?id=200935

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Copy with rsync over ssh

From remote server to local one:

rsync -avzhe ssh remote_user@REMOTE_IP:/remote_folder_or_file /local_destination_folder_or_file

From local server to remote one:

rsync -avzhe ssh local_folder_or_file remote_user@REMOTE_IP:/remote_destination_folder_or_file

That’s it, Enjoy!

Sources:

Rsync (Remote Sync): 10 Practical Examples of Rsync Command in Linux

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