Linux

Nginx: worker_connections are not enough, reusing connections

We meet an error log on nginx: worker_connections are not enough, reusing connections. To resolve this issue, here is my working solution according to the references:

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By Yu, 2 years2 years ago

Avoid stuck after ‘SSH2_MSG_SERVICE_ACCEPT received’

It is becoming pretty slow in SSH to a CentOS server.

Trying to print a verbose log:

$ ssh -vvvv my-host
....
debug3: send packet: type 21
debug2: set_newkeys: mode 1
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug3: receive packet: type 21
debug1: SSH2_MSG_NEWKEYS received
debug2: set_newkeys: mode 0
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: /Users/user/.ssh/id_rsa RSA SHA256:XXXXX/gNY explicit
debug2: pubkey_prepare: done
debug3: send packet: type 5
debug3: receive packet: type 7
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug3: receive packet: type 6
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug3: send packet: type 50
..... <<<-- long long long silence here
debug3: receive packet: type 51 <<<-- and then continue to access the server
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug3: start over, passed a different list publickey,gssapi-keyex,gssapi-with-mic,password
debug3: preferred publickey,keyboard-interactive,password

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By Yu, 3 years2 years ago

SSH port forwarding

SSH Port Forwarding is a mechanism in SSH for tunneling application ports from the client machine to the server machine, or vice versa.

Suppose we wish to visit a port on a remote machine that is behind a firewall; we can use SSH port forwarding to bind that port to our local machine.

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By Yu, 7 years7 months ago

A Cheat Sheet Regarding to System Hardware info

This post lists a few examples to check the status of your system in macOS and Linux

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By Yu, 7 years2 years ago

Invoke sudo access to one user/group without password

sudo allows a system administrator to delegate authority to give certain users—or groups of users—the ability to run commands as root or another user while providing an audit trail of the commands and their arguments. It plays a vital role in user controlling. (more…)

By Yu, 7 years2 years ago

Code

Here document, another way to write multiline into one file

Here documents are indeed a powerful feature in Unix-like operating systems, allowing for the efficient creation and manipulation of files from within a shell script. They are particularly useful when you need to insert multiple lines of text into a file without having to resort to looping constructs or temporary files.

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By Yu, 8 years4 months ago