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Boot from grub in CentOS 7
After my CentOS 7 upgrade, I rebooted it. It gets stuck and shows a prompt like this:
grub >
It is an annoying start.
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Lazy Initialize Data Attributes in Python
Suppose we want to create a "lazy" data attributes ( "instance variables" in Smalltalk, or "data members" in C++) in a Python Class. We may required to use getattr to customize attribute access.
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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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从源码编译 golang
首先下载 golang 的代码，可以从 https://golang.org/dl 或者中国的 mirror https://golang.google.cn/dl 下载最新的 go<version>.src.tar.gz. 然后开始编译就可以。
构建方法基本可以参考官方文档 就可以。
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Initialize Jetson Nano Environment
If we use Jetson Nano's default image to start our project, we may have some follow steps to make our work easier.
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Go Proxy Configurations
To speed up our dependencies updating for golang, or prepare some patterns for our special libraries, we probably consider to use a proxy to speed it up.
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The short-circuiting in bash
Bash script writing is a import approach to configure the linux system. Suppose we wish to add a user if not exists, the command may seems as follow:
TARGET_USER=alice
if (! id -u $TARGET_USER > /dev/null 2>&1 ); then
echo "creating user $TARGET_USER"
# adduser $TARGET_USER
fi
However, it is kind of too long. In this case short-circuiting is a alternative solution. (more…)
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A simple workflow to create a clean python library based on Anaconda
The open-source Anaconda Distribution is an easy way to perform Python/R data science and machine learning on Linux, Windows, and Mac OS X. We could easily prepare an isolated and constant environment on anywhere based on a configure file.
Considering the various kind of strange errors due to the different versions of python and python libraries, this management tool makes our life much more comfortable in deploying and cooperating.
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How to keep the Ubuntu laptop on working
We may edit the configure file "/etc/systemd/logind.conf" and change one line from
#HandleLidSwitch=suspend
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Gracefully shutdown a http server in golang
To gracefully shutdown a http server requires a few steps.
The http library's serving function will block over there when getting started, until we call http.Server.Close(). As for us, we can invoke the starting function in a goroutine, and call close in another one.