[Shell] What is a shell?

I hope not white piao, the point of a brush praise or comments to walk, as well as prohibit [Reserved]
This article is to introduce the history of the shell, if you really want to have to shell understanding on combat, look at my other [shell ] beginning of the article (note I do more, made only slowly, if there is a particular need a certain aspect, you can reply in the comments, if I have the relevant information I will give priority to the issue)

What is the operation and maintenance?

Glossary terms

Linux distributions have what

Kind of shell

Speaking shell, it first reaction should be a scripting language, in fact, I personally do not agree. What is the script? In the final analysis is a program, he can realize the function, java can also write the script, but is it necessary to compile a waste of time, relatively speaking. After all, industry specializing in surgery, but said with a shell that language to develop a number of relatively small program is very convenient. In fact, I think this is the intention of the scripting language

What is the operation and maintenance? (Work can ignore this)

When it comes to operation and maintenance work for its white for you think he is playing shell, of course, there are other languages, after all, language is a tool. It's a lot of functions, such as cut traffic on the line, machine maintenance, data backup and so on and so on, each company defined for each position is different, but in general are the same. Next we specifically say what is the operation and maintenance:

This map I think is very wide, and this is the earliest I started to learn shell, consequently do not know when not know where to find the map. In fact, I have not read a lot, of course, is now understood about each, but these are some of the manufacturers, as you work you will slowly come into contact with these things, whether you are testing or development will deal with them, so here to do an understanding enough .

Glossary terms

The following content may be relatively long (I just saved you read above to check the time, after all, do not look at this work, have not read the full white blind search), to be honest I do not want to see because he says it useful it really is futile, he said he was useless it really useful. You say you work when people tell the IDC you have to think about what it is, is not it embarrassing?

• IDC- (Internet Data Center) Internet data center, the main services include machine rental, server hosting, rack rental, room rental, dedicated access and network management services. IDC business in the broad sense, in fact, all the services provided by the data center. Rental server and client bandwidth data centers, data centers and use technology to achieve their demands on hardware and software, build their own Internet platform, enjoy a range of services provided by the data center.
• ISP- (Internet Service Provider) Internet service providers, namely the user to provide Internet access services, information services, telecom operators and value-added services.
• ICP- (Internet Content Provider) Internet content provider, to provide customers with comprehensive Internet information services and value-added services for telecom operators. According to People's Republic of China State Council Order No. 292, "Internet Information Services" stipulates that the state licensing system for providing Internet information services ICP. Thus, become the ICP license website operators license, operating site must apply for ICP license, otherwise it is illegal operators. Therefore, for the ICP license is a legitimate business need for corporate website.
• CDN- (Content Delivery Network) content distribution network, relying deployed around the edge server, load balancing through the center of the platform, content distribution, scheduling and other functional modules, allowing users to get what you need nearby, reduce network congestion and improve user access response speed and hit rate. The key technology of CDN main content storage and distribution technologies. The basic principle is widely used in a variety of CDN cache server, the cache server distributed to these regions with relatively dense user access or network when the user accesses the site, the user's access technology utilizing the global load will point to the nearest working properly cache on the server, the cache server in response to direct user requests.
• LVS- (Linux Virtual Server) shorthand, which means Linux virtual server is a virtual server cluster. LVS cluster IP load balancing technology and the use of content-based request distribution technology. The scheduler has a good throughput, a balanced transfer request to a different server to perform, and the scheduler failed server automatically masked, thereby constituting a group of servers is a high-performance, high-availability virtual server. Structure of the entire server cluster is transparent to customers, but without modifying the client and server-side program. For this reason, the design considerations of the system transparency, scalability, high availability and ease of management.
• CGI- (Common Gateway Interface) Common Gateway Interface. CGI specification allows Web server to execute external programs, and send their output to the Web browser, the Web is a set of CGI simple static hypermedia document into a complete new interactive media
• GSLB- (Global Server Load Balance, global load balancing) CDN system architecture as the core part, responsible for traffic scheduling. GSLB vast majority of DNS-based applications using load balancing techniques are used to access the destination host by domain name, the user issued when any application connection requests, the request must first be obtained through DNS server IP address, it is to make intelligent decisions in return DNS resolution result of the process of DNS-based GSLB, a return to the user the best service IP. User application processes and the absence of any GSLB unchanged. This is also the mainstream GSLB technology on the market.
• BOSS- (Business & Operation Support System, BOSS) is a business operation support system. Commonly referred to as BOSS is divided into four parts: billing and settlement system, operating and accounting systems, customer service systems and decision support systems. From a business perspective BOSS is a framework for bearer traffic systems, CRM systems, billing systems. Achieve longitudinal, transverse unified management framework. The system was first proposed by the billing system evolved from the telecom sector development, basic functions include customer information management, product management, subscription management, billing, out of account and settlement, is responsible for registering customer information, manage user subscription service delivery, real-time depending on the product, the standard tariff package computing business (mobile phone, fixed phone users call, on-demand viewing, broadband traffic and time, etc.) of the amount of consumption, the quasi-real-time billing and regular user computing, real-time or periodic settlement of various users consumption costs.

Linux distributions

Linux, of course not the same, just like you buy a computer graphics He also points many manufacturers, generally you can see is the following:

• RedHat: Fedora, CentOS, Mandriva
• SuSE: SLES, OpenSuSE
• Debian: Ubuntu
• BackTrace / kali linux (hackers)
  mostly centos work, training courses mostly ubuntu (visual interface to do a good job), the other to be honest I have not used, it is not care, after all, we just the deployment code on the environment, nor to study how to write kernel.

Kind of Shell

There are also a variety of shell, probably under so much, in fact, used in Kazakhstan is not a bash shell with zsh, at least not encountered in my years of experience inside over anything else. I am now in use zsh mac system is also installed, as to zsh installation here I do not say, I do have a hand installation tutorial fool, but do need time to sort out, I slowly come will be issued, anxious not to catch .
1.sh (Bourne Shell): Steve Bourne developed by a variety of UNIX systems are equipped with sh.
2.csh (C Shell): Joy developed by Bill, released with BSD UNIX, its flow control statements like the C language, Bourne Shell supports many features that are not supported: job control, command history, command line editing.
3.ksh (Korn Shell): developed by the David Korn, sh backward compatibility features, and adds new features introduced csh, many UNIX system is the standard configuration of Shell, on these systems / bin / sh is often the point / bin / ksh symbolic link.
4.tcsh (TENEX C Shell): it is an enhanced version of csh, the introduction of command completion etc., replacing csh on FreeBSD, Mac OS X systems.
5.bash (Bourne Again Shell): developed by the GNU Shell, the main goal is to maintain consistency with the POSIX standard, taking into account the compatibility of sh, bash from the csh and ksh learn a lot of features, a variety of Linux distributions standard configuration Shell, on the Linux system / bin / sh often point to / bin / bash symbolic link. Nevertheless, bash and sh still have a lot of different, on the one hand, extends the bash commands and parameters, on the other hand, bash and sh not fully compatible, some behavior is not consistent, so bash sh need to simulate the behavior: When we by the time the program name sh start bash, bash can pretend to be sh, do not recognize the extended commands and behavior consistent with sh.
6.zsh of command completion is very powerful, it can be filled path, filled orders, filled parameters.
vim / etc / passwd
where the user last column shows the corresponding shell type
root❌0: 0: the root: / the root: / bin / the bash
nobody❌65534: 65534: the nobody: / NONEXISTENT: / bin / SH
syslog❌101: 103 :: / Home / the syslog: / bin / to false
itcast❌1000: 1000: itcast,: / Home / itcast: / bin / the bash
ftp❌115: 125: FTP daemon,: / SRV / FTP: / bin / to false