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mysqlcheck: Got error: 1045: Access denied for user ‘root’@’localhost’ (using password: YES) when trying to connect

This error occurs when I run the following command:

Note that the command prompts for a password, and I input the correct password for the user root. Why does it still deny the access for root? If you ran

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set up v2ray with ws+tls

The idea  is your computer running v2ray client sends traffic to an https website address like https://domainhostseotool.com/ray. This website returns normal website content except for location /ray. For this special location, the httpd server Apache behaviors as a reverse proxy

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journalctl Failed to open files: Protocol not supported

After upgrading systemd from V219 to v247, journalctl stops working: journalctl -u v2ray Journal file /var/log/journal/xxxx/user-1000.journal uses an unsupported feature, ignoring file. Use SYSTEMD_LOG_LEVEL=debug journalctl –file=/var/log/journal/xxxx/user-1000.journal to see the details. SYSTEMD_LOG_LEVEL=debug journalctl –file=/var/log/journal/xxxx/user-1000.journal Journal effective settings seal=no keyed_hash=yes compress=no compress_threshold_bytes=8B

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How to upgrade systemd on CentOS 7?

First, you should know how to check systemd version on Linux. The system version command is:

You will see the output is “systemd 219″ on CentOS 7. This version is too low for many software that depend on systemd.

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How to use pip to uninstall package and install specific version of package?

You must know how to install a package with pip:

This will install the package components mainly to /usr/local/lib/python3.6/site-packages/xxx/, as well as some files to /usr/local/bin/, /usr/local/share/man/ and /usr/local/share/polkit-1/actions/. pip3 install command installs the latest version of package. If

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Proftpd DefaultRoot

In proftpd.conf, there is a line

You can guess what DefaultRoot means. It means the default directory when an ftp client logs in. “DefaultRoot ~” means when a user connects and logs in ftp, it comes at his home

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Difference between hard link and symbolic link

I thought hard link is alias of a file and symbolic link is another file pointing to the linked file. So, I thought using symbolic link may be safer than using hard link. I thought “rm -f symlink” just delete

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How to setup apache proxy server?

When talking about apache proxy, we usually mean apache forward proxy. There is another kind of apache proxy: apache reverse proxy. The difference between apache forward proxy and apache reverse proxy is that apache forward server accepts connections from clients

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apachectl fullstatus

I never used “apachectl fullstatus” before. To get httpd status, I used “service httpd status” or “service httpd status -l” or “systemctl status httpd”. But now, I want to get more information about apache. You may hear about apache2ctl, but

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ERROR: cannot verify curl.se’s certificate, issued by “/C=US/O=Let’s Encrypt/CN=R3”:Issued certificate has expired.

When you wget some url such as:

, you may get this error: ERROR: cannot verify curl.se’s certificate, issued by “/C=US/O=Let’s Encrypt/CN=R3”:Issued certificate has expired. This is because the server of this url uses Let’s Encrypt issued certificate, while

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