#135 Linux 分区方案(Partition Scheme)
Linux 2016-05-14安装 Ubuntu 16.04 时选择的分区方案。
挂载点 | 大小 | 意义 |
---|---|---|
/ |
50GB | 根目录 |
/boot |
10GB | 启动目录 |
/home |
150GB | 用户主目录 |
/usr |
100GB | 程序分区 |
/var |
50GB | 变量文件目录 |
/tmp |
50GB | 临时文件目录 |
SWAP |
20GB | 交换分区 |
coding in a complicated world
安装 Ubuntu 16.04 时选择的分区方案。
挂载点 | 大小 | 意义 |
---|---|---|
/ |
50GB | 根目录 |
/boot |
10GB | 启动目录 |
/home |
150GB | 用户主目录 |
/usr |
100GB | 程序分区 |
/var |
50GB | 变量文件目录 |
/tmp |
50GB | 临时文件目录 |
SWAP |
20GB | 交换分区 |
在命令行中输出颜色文字。
关于 DNF 的更多信息,参考:2016/05/03 CentOS DNF
.rpm
包,和 .deb
包是 Linux 生态中两种最主要的包格式。bash-4.2.46-35.el7_9.x86_64.rpm
其中:
名称 :bash
架构 :x86_64
版本 :4.2.46
发布 :31.el7
大小 :3.5 M
源 :installed
来自源:anaconda
简介 : The GNU Bourne Again shell
网址 :http://www.gnu.org/software/bash
协议 : GPLv3+
描述 : The GNU Bourne Again shell (Bash) is a shell or command language
: interpreter that is compatible with the Bourne shell (sh). Bash
: incorporates useful features from the Korn shell (ksh) and the C shell
: (csh). Most sh scripts can be run by bash without modification.
yum help list # 查看帮助
yum search <package> # 搜索包
yum list
yum list installed
rpm -qa
yum list --upgradable
yum info <package>
rpm -qi <package>
rpm -ql <package> # 已安装包的文件列表
rpm -qd <package> # 已安装包的文件列表中的文档部分
rpm -qc <package> # 已安装包的文件列表中的配置部分
yum repolist
# repoquery 是 yum-utils 包提供的命令
repoquery -l <package> # 文件列表
repoquery -f <filepath> # 查看文件属于哪个包, 比如: `repoquery -f "*/repoquery"`
repoquery --location <package> # 查看包的下载地址
yum deplist <package> # 依赖
rpm -qR <package> # 已安装包的依赖
rpm -q --whatrequires <package> # 反向依赖
rpm -q --whatprovides <filepath>
rpm -qf <filepath>
yum provides <pattern>
yum whatprovides <patter>
yum check-update
yum updateinfo
yum update [package]
yum upgrade [package]
yum update-minimal
yum upgrade-minimal # 和 yum update-minimal 相同
yum downgrade <package>
yum install <package>
yum install <package-rpm-filepath>
yum reinstall
yum makecache
yum clean
yum erase
yum remove
yum autoremove
# list, info, summary, repeat, redo, undo, new, rollback, addon, addon-info, stats, statistics, sync, synchronizepkg, pkgs, pkg-list, pkgs-list, package, package-list, packages, packages-list, pkg-info, pkgs-info, package-info, packages-info
yum history
yum history list
yum history list all
yum versionlock <package>
RedHat 系列提供的,安装组(Group)的概念非常好。
安装组就是为了某一个目的需要的一组包,比如 gnome-desktop 组是安装一个完整的 gnome 桌面环境,web-server 组是安装 apache 和相关的几个包。
$ yum help groups
groups [list|info|summary|install|upgrade|remove|mark] [GROUP]
显示或使用、组信息
别名:group, grouplist, groupinfo, groupinstall, groupupdate, groupremove, grouperase
yum grouplist
yum group list ids
附带组 IDyum group list hidden
列出所有组yum groupinfo
yum groupinstall <group>
yum install @<group>
yum install @^<environment-group>
yum --setopt=group_package_types=mandatory,default,optional groupinstall "Web Server"
yum groupupdate
yum groupremove
yum grouperase
/etc/yum.conf
/etc/yum.repos.d/
/etc/yum/
/etc/rpm 目录不知道是干什么的。
比如最常见的 fastestmirror,用于自动选择最快的镜像源。所以我们使用 CentOS 时,一般不需要去配置镜像源。
复制指定 URL 路径下的所有文件到本地目录 HTML 下:
wget -m -p -k -np -P <HTML> <URL>
Nginx 商用版 1.5.7 (2013 年) 开始支持 sticky 指令。
文档: https://nginx.org/en/docs/http/ngx_http_upstream_module.html#sticky
Syntax: sticky cookie name [expires=time] [domain=domain] [httponly] [samesite=strict|lax|none] [secure] [path=path];
sticky route $variable ...;
sticky learn create=$variable lookup=$variable zone=name:size [timeout=time] [header] [sync];
Default: —
Context: upstream
开源版有 nginx-sticky-module。
C 语言写的,BSD 协议。
代码看起来并不复杂,如果需要用到的时候,可以进行一个粗略的 Review。
# 下载 nginx 源码 (2016-04-26)
wget http://nginx.org/download/nginx-1.10.0.tar.gz http://nginx.org/download/nginx-1.10.0.tar.gz.asc
gpg --verify nginx-1.10.0.tar.gz.asc
# 下载 nginx-sticky-module (2015-08-06)
wget https://bitbucket.org/nginx-goodies/nginx-sticky-module-ng/get/1.2.6.zip
unzip 1.2.6.zip
cd nginx-goodies-nginx-sticky-module-ng-c78b7dd79d0d/
unzip nginx-1.10.0.zip
cd nginx-1.10.0/
# 其他参数按需添加
./configure --add-module=../nginx-goodies-nginx-sticky-module-ng-c78b7dd79d0d/
make && make install
# Configuration summary
# + using system PCRE library
# + OpenSSL library is not used
# + md5: using system crypto library
# + sha1: using system crypto library
# + using system zlib library
# nginx path prefix: "/usr/local/nginx"
# nginx binary file: "/usr/local/nginx/sbin/nginx"
# nginx modules path: "/usr/local/nginx/modules"
# nginx configuration prefix: "/usr/local/nginx/conf"
# nginx configuration file: "/usr/local/nginx/conf/nginx.conf"
# nginx pid file: "/usr/local/nginx/logs/nginx.pid"
# nginx error log file: "/usr/local/nginx/logs/error.log"
# nginx http access log file: "/usr/local/nginx/logs/access.log"
# nginx http client request body temporary files: "client_body_temp"
# nginx http proxy temporary files: "proxy_temp"
# nginx http fastcgi temporary files: "fastcgi_temp"
# nginx http uwsgi temporary files: "uwsgi_temp"
# nginx http scgi temporary files: "scgi_temp"
upstream {
sticky;
server 127.0.0.1:9000;
server 127.0.0.1:9001;
server 127.0.0.1:9002;
}
sticky [name=route] [domain=.foo.bar] [path=/] [expires=1h]
[hash=index|md5|sha1] [no_fallback] [secure] [httponly];
ABO 血型系统是根据血小板上的两种抗原——A 抗原和 B 抗原——来区分的:
A 型血的人会消灭 B 抗原,所以不能输 B 型血和 AB 型血,只能输 A 型血和 O 型血;
同理,B 型血的人会消灭 A 抗原,所以不能输 A 型血和 AB 型血,只能输 B 型血和 O 型血;
AB 型血的人自己就两种抗原都有,当然都不消灭,所有血型的血都可以;
相反,O 型血的人两种抗原都没有,哪种都不可接受,所以只能使用 O 型血。
No | 父/母 | 父/母 | 子女 | 子女 | 子女 | 子女 |
---|---|---|---|---|---|---|
1 | O | O | O | - | - | - |
2 | O | A | O | A | - | - |
3 | O | B | O | - | B | - |
4 | O | AB | - | A | B | - |
5 | A | A | O | A | - | - |
6 | A | B | O | A | B | AB |
7 | A | AB | - | A | B | AB |
8 | B | B | O | - | B | - |
9 | B | AB | - | A | B | AB |
10 | AB | AB | - | A | B | AB |
一共 10 种组合:
生 O 型血子女的组合有 6 种
生 AB 型血子女的组合有 4 种
AB 型血父母不能生 O 型血子女
牛耕田回来,躺在栏里,疲惫不堪地喘着粗气,狗跑过来看它。
“唉,老朋友,我实在太累了。”牛诉着苦,“明儿个我真想歇一天。”
狗告别后,在墙角遇到了猫。狗说:“伙计,我刚才去看了牛,这位大哥实在太累了,它说它想歇一天。也难怪,主人给它的活儿太多太重了。”
猫转身对羊说:“牛抱怨主人给它的活儿太多太重,它想歇一天,明天不干活儿了。”
每次春晚都必然问候海外华人华侨,但我从来没有思考过华人和华侨有什么区别,近日看到网络上的一些资料才弄明白。
# 时间清零
touch -amt 197001010000.00 <file>
sudo apt install -y xattr
xattr -l <file>
# 删除所有附加属性
xattr -c <file>
ess-cue-el
, 但至今为止,不少人还是将其读做 /ˈsiːkwəl/
。SQL-86 (or SQL-87) is the ISO 9075:1987 standard of 1987
SQL-89 is the ISO/IEC 9075:1989 standard of 1989
SQL-92 is the ISO/IEC 9075:1992 standard of 1992
SQL:1999 is the ISO/IEC 9075:1999 standard of 1999
SQL:2003 is the ISO/IEC 9075:2003 standard of 2003
SQL:2006 is the ISO/IEC 9075:2006 standard of 2006
SQL:2008 is the ISO/IEC 9075:2008 standard of 2008
SQL:2011 is the ISO/IEC 9075:2011 standard of 2011
SQL:2016 is the ISO/IEC 9075:2016 standard of 2016
Year | Name | Alias | Comments |
---|---|---|---|
1986 | SQL-86 | SQL-87 | First formalized by ANSI |
1989 | SQL-89 | Minor revision that added integrity constraints | |
1992 | SQL-92 | SQL2 | Major revision (ISO 9075) |
1999 | SQL:1999 | SQL3 | |
2003 | SQL:2003 | ||
2006 | SQL:2006 | ||
2008 | SQL:2008 | ||
2011 | SQL:2011 | ||
2016 | SQL:2016 | ||
2019 | SQL:2019 |
SQL:1999
Added regular expression matching, recursive queries (e.g. transitive closure), triggers, support for procedural and control-of-flow statements, nonscalar types (arrays), and some object-oriented features (e.g. structured types), support for embedding SQL in Java (SQL/OLB) and vice versa (SQL/JRT)
2003
Introduced XML-related features (SQL/XML), window functions, standardized sequences, and columns with autogenerated values (including identity columns)
2006
ISO/IEC 9075-14:2006 defines ways that SQL can be used with XML. It defines ways of importing and storing XML data in an SQL database, manipulating it within the database, and publishing both XML and conventional SQL-data in XML form. In addition, it lets applications integrate queries into their SQL code with XQuery, the XML Query Language published by the World Wide Web Consortium (W3C), to concurrently access ordinary SQL-data and XML documents.
2008
Legalizes ORDER BY outside cursor definitions. Adds INSTEAD OF triggers, TRUNCATE statement,[34] FETCH clause
2011
Adds temporal data (PERIOD FOR)[35] (more information at: Temporal database#History). Enhancements for window functions and FETCH clause.
2016
Adds row pattern matching, polymorphic table functions, JSON
2019
Adds Part 15, multidimensional arrays (MDarray type and operators)
https://en.wikibooks.org/wiki/Structured_Query_Language
https://en.wikibooks.org/wiki/MySQL
https://en.wikibooks.org/wiki/PostgreSQL
https://en.wikibooks.org/wiki/SQLite
https://en.wikipedia.org/wiki/SQL_reserved_words
最新的 SQL 标准一共分成 9 个部分(Part 5,6,7,8,12 可能是被废弃了):
PS: 前缀 ISO/IEC 9075-<n>:2016 – Information technology – Database languages – SQL –
省略。
PS: 还有一个拓展标准:ISO/IEC 13249 SQL Multimedia and Application Packages
多数数据库没有严格按照标准来实现,导致不通平台上的 SQL 语句是不能跨平台的。
以下是两种主要的 SQL 方言: