TranslateProject/sources/talk/20141223 20 Linux Commands Interview Questions & Answers.md

20条Linux命令面试问答
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**问:1 如何查看当前的Linux服务器的运行级别？**

答: ‘who -r’ 和 ‘runlevel’ 命令可以用来查看当前的Linux服务器的运行级别。

**问:2 如何查看Linux的默认网关？**

答: 用 “route -n” 和 “netstat -nr” 命令，我们可以查看默认网关。除了默认的网关信息，这两个命令还可以显示当前的路由表。

**问:3 如何在Linux上重建初始化内存盘影响文件？**

答: 在CentOS 5.X / RHEL 5.X中，可以用mkinitrd命令来创建初始化内存盘文件，举例如下：

    # mkinitrd -f -v /boot/initrd-$(uname -r).img $(uname -r)

如果你想要给特定的内核版本创建初始化内存盘，你就用所需的内核名替换掉 ‘uname -r’ 。

在CentOS 6.X / RHEL 6.X中，则用dracut命令来创建初始化内存盘文件，举例如下：

    # dracut -f

以上命令能给当前的系统版本创建初始化内存盘，给特定的内核版本重建初始化内存盘文件则使用以下命令：

    # dracut -f initramfs-2.x.xx-xx.el6.x86_64.img 2.x.xx-xx.el6.x86_64

**问:4 cpio命令是什么？**

答: cpio就是复制入和复制出的意思。cpio可以向一个归档文件（或单个文件）复制文件、列表，还可以从中提取文件。

**问:5 patch命令是什么？如何使用？**

答: 顾名思义，patch命令就是用来将修改（或补丁）写进文本文件里。Patch命令通常是接收diff的输出并把文件的旧版本转换为新版本。举个例子，Linux内核源代码由百万行代码文件构成，所以无论何时，任何代码贡献者贡献出代码，只需发送改动的部分而不是整个源代码，然后接收者用patch命令将改动写进原始的源代码里。

创建一个diff文件给patch使用，

    # diff -Naur old_file new_file > diff_file

旧文件和新文件要么都是单个的文件要么都是包含文件的目录，r选项支持目录树递归。

一旦diff文件创建好，我们就能在旧的文件上打上补丁，把它变成新文件：

    # patch < diff_file

**问:6 aspell有什么用 ?**

答: 顾名思义，aspell就是Linux操作系统上的一款交互式拼写检查器。aspell命令继任了更早的一个名为ispell的程序，并且作为一款嵌入式替代品，最重要的是它非常好用。While the aspell program is mostly used by other programs that require spell-checking capability, it can also be used very effectively as a stand-alone tool from the command line.

**问:7 How to check the SPF record of domain from command line ?**

答: We can check SPF record of a domain using dig command. Example is shown below :

    linuxtechi@localhost:~$ dig -t TXT google.com

**问:8 How to identify which package the specified file (/etc/fstab) is associated with in linux ?**

答: # rpm -qf /etc/fstab

Above command will list the package which provides file “/etc/fstab”

**问:9 Which command is used to check the status of bond0 ?**

答: cat /proc/net/bonding/bond0

**问:10 What is the use of /proc file system in linux ?**

答: The /proc file system is a RAM based file system which maintains information about the current state of the running kernel including details on CPU, memory, partitioning, interrupts, I/O addresses, DMA channels, and running processes. This file system is represented by various files which do not actually store the information, they point to the information in the memory. The /proc file system is maintained automatically by the system.

**问:11 How to find files larger than 10MB in size in /usr directory ?**

答: # find /usr -size +10M

**问:12 How to find files in the /home directory that were modified more than 120 days ago ?**

答: # find /home -mtime +l20

**问:13 How to find files in the /var directory that have not been accessed in the last 90 days ?**

答: # find /var -atime -90

**问:14 Search for core files in the entire directory tree and delete them as found without prompting for confirmation**

答: # find / -name core -exec rm {} \;

**问:15 What is the purpose of strings command ?**

答: The strings command is used to extract and display the legible contents of a non-text file.

**问:16 What is the use tee filter ?**

答: The tee filter is used to send an output to more than one destination. It can send one copy of the output to a file and another to the screen (or some other program) if used with pipe.

    linuxtechi@localhost:~$ ll /etc | nl | tee /tmp/ll.out

In the above example, the output from ll is numbered and captured in /tmp/ll.out file. The output is also displayed on the screen.

**问:17 What would the command export PS1 = ”$LOGNAME@`hostname`:\$PWD: do ?**

答: The export command provided will change the login prompt to display username, hostname, and the current working directory.

**问:18 What would the command ll | awk ‘{print $3,”owns”,$9}’ do ?**

答: The ll command provided will display file names and their owners.

**问:19 What is the use of at command in linux ?**

答: The at command is used to schedule a one-time execution of a program in the future. All submitted jobs are spooled in the /var/spool/at directory and executed by the atd daemon when the scheduled time arrives.

**问:20 What is the role of lspci command in linux ?**

答: The lspci command displays information about PCI buses and the devices attached to your system. Specify -v, -vv, or -vvv for detailed output. With the -m option, the command produces more legible output.

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via: http://www.linuxtechi.com/20-linux-commands-interview-questions-answers/

作者：[Pradeep Kumar][a]
译者：[ZTinoZ](https://github.com/ZTinoZ)
校对：[校对者ID](https://github.com/校对者ID)

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[a]:http://www.linuxtechi.com/author/pradeep/
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