Linux配置与故障排查：初学者指南

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本资源是一份名为"Linux of assessment test.pdf"的文档，主要针对Linux系统的评估测试，旨在通过具体的题目帮助初学者提升Linux操作技能。以下是部分题目及其知识点详解： 1. 题目：如何临时停止postfix服务器以进行配置更改？ - 答案选项：A、C、D - 解析：在Linux中，`stop postfix`命令通常用于停止服务，`xinetdpostfix stop`可能是一种管理方式（如果xinetd是postfix的服务管理器），而`/etc/rc.d/postfix stop`是Linux系统初始化脚本中用来控制服务启动/停止的方法。`kill-9 postfix`是一个强制退出程序的命令，不建议用于此场景，因为它会终止进程而非临时停止。 2. 如何检查与第二块以太网设备（eth1）相关的最近内核消息？ - 答案：C - 解析：在Linux中，`dmesg | grep eth1`命令用于查看内核日志（dmesg）中包含eth1相关信息的部分，这可以帮助查找与该设备相关的错误或调试信息。 3. initrd线在GRUB配置中的作用是什么？ - 答案：D - 解释：initrd是Initial RAM Disk的缩写，它是在引导过程中加载到内存中的只读根文件系统。GRUB配置中的initrd行指示了GRUB应从哪里找到初始RAM磁盘，这个磁盘包含了引导过程中使用的内核模块和配置文件，确保在加载完整个硬盘上的操作系统之前，这些文件能被正确加载。通过这份评估测试，学习者可以了解到Linux系统管理、网络设备监控以及引导过程中的关键技术细节。对于初学者来说，这些题目既能巩固基础知识，也有助于理解实际应用场景。通过解答这些问题，可以提升对Linux系统命令行操作和底层原理的理解。

employees of your company. What file would you edit to deliver this message before Telnet users see a

/etc/profile.net

/etc/profile

/etc/issue.net

/etc/issue

20.

In reviewing files in /etc, you find that /etc/motd is completely empty. What does this mean?

The system won’t display a message of the day after users log in.

Morton’s Own Temporary Documentation is not installed on the system.

The motd.conf file’s name has become corrupted and its contents lost.

Users will see no witty aphorisms appear on the screen after logging in.

Answers to Review

Questions

D. By default, the kernel launches the /sbin/init program as its first process, as option D specifies.

This program handles the rest of the system startup process, including launching SysV or Upstart startup

scripts. Options A, begin, and C, Startup, are fictitious programs. Option B’s startx is a user script that’s

used to start the X server after a text-mode login; it’s not involved in the system startup process.

B. GRUB enables you to edit its entries on a one-time basis by selecting them and pressing the E key, as

specified in option B. Options A and C both describe fictitious procedures. (Although Windows provides a

tool called the Recovery Console, Linux does not.) Because option B is correct, option D cannot

be—although of course reinstalling Linux would

fix

the

problem but hardly in a simple way.

A. Option A describes one method of booting into single-user mode. (It’s also possible to create a

permanent GRUB entry for single-user mode that you can select more directly.) Options B, C, and D all

describe fictitious actions that would have no effect. (Option C describes a boot: prompt, which is a feature

of the older Linux Loader, LILO, not of GRUB.)

C. The /etc/inittab specifies the initial runlevel on its id line, as stated in option C. The

/etc/fstab file of option A holds information on filesystems and their mount points. The

/etc/init.d/runlevel and /etc/runlevel files of options B and D are both fictitious.

D. Pressing the C key enters GRUB’s interactive mode, as option D specifies. The other options do

not have this effect.

C. When a system uses GRUB 2, system administrators are

encouraged to edit /etc/grub.d/40_custom to add custom GRUB configurations for locally compiled

kernels or unusual OSs. After making such a change, you should type update-grub to update the GRUB

run-time configuration file, /boot/grub/grub.cfg. Option A is a fictitious file. Options B and D are two

names for the GRUB Legacy configuration file; editing them has no effect on GRUB 2.

A. The id line in /etc/inittab specifies the default runlevel, which in this example is 3, as specified in

option A. Although runlevel 3 is a text-mode-only runlevel on Red Hat and related distributions, as option

B specifies, this isn’t true of all distributions; Debian,

Ubuntu,

Gentoo, and others control the startup of X

in ways other than by the default runlevel. Thus, option B is not a correct answer. Option C describes the

effect of setting the default runlevel to 0, not to 3, so it is incorrect. The /etc/inittab file is a standard

part of the SysV startup system, and it’s present on some Upstart-based systems. Thus, the presence of

this file, or the presence of the specified line in this file, is not diagnostic of an Upstart-based system, and

option D is incorrect.

B. The /etc/init.d directory holds SysV startup scripts on many Linux systems, as option B specifies.

Upstart startup scripts reside in /etc/init or /etc/event.d, so option A is incorrect. User login scripts are

stored in the users’ home directories under various names, so option C is incorrect. System login names

reside in /etc or subdirectories of it, usually under names related to the shell, but not in /etc/init.d, so

option D is incorrect.

C, D. Options C and D both specify directories where runlevel-specific symbolic links to SysV startup

scripts may reside (the ? is a stand-in for a runlevel number), depending on the

distribution in use. The /etc/inittab file is the configuration file for init in the SysV startup system, but

it doesn’t hold symbolic links, so option A is incorrect. The /etc/init directory holds Upstart scripts on

Upstart-based systems, not SysV startup scripts or links to them, so option B is incorrect.

10.

A. The chkconfig command displays information on or modifies the status of services started by

SysV startup scripts. The --list option displays the status of a service by the specified name, so

option A does as the question asks. The info command is a system documentation

tool; option B displays the info page, if it’s

present,

for the waiter command, which is not what the

question asks. Option C displays process information on any processes called waiter or that include the

string waiter in the command line. This won’t reveal in what runlevels these processes run, so option C is

incorrect. The runlevel command displays the current and previous runlevel, but it won’t tell you in

which runlevels a particular program runs, so option D is incorrect.

11.

B, C, D. Runlevels 2, 3, and 5 are all reasonable default runlevels, because

they all correspond to working multi-user modes. Debian and related distributions generally use runlevel 2

as a default, and runlevels 3 and 5 are generally used as defaults without

and

with

X running, respectively,

on Red Hat and related distributions. Runlevel 0 is not a reasonable default, since runlevel 0 corresponds to

system shutdown; if you set it as the default, the system will shut down as soon as it boots. Thus, option A is

not correct.

12.

D. The update-rc.d utility affects the runlevels in which services run. It takes a service name, an

action, and a runlevel or list of runlevels as arguments. Thus,

enable is a service name, albeit a confusing

one, and disable is a command to disable the service. This command is applied to runlevels 2 and 3.

Option D describes this effect, and the remaining options do not.

13.

C. Source code that’s compiled locally is traditionally extracted to

/usr/src

into

a subdirectory named after the package to be installed. Thus, option C is correct, although there’s no

guarantee that the relevant directory will be found—it’s possible the previous administrator deleted the

files or used a non-standard location to compile them. Option A describes a

temporary holding location for source tarballs on a Gentoo Linux system, but it’s not a likely location for

a source directory on a Fedora system, so this option is incorrect. The /var/lib/rpm directory is used by

RPM to store its package database and related files, but it’s not a likely location for an administrator

to extract source code for local compilation, so option B is incorrect. Binaries that are

distributed in tarball form are sometimes installed in /opt, but this isn’t a standard location for source code,

so option D is incorrect.

14.

D. Many programs have an uninstall target to make, meaning that if you do

option

D suggests, the

software will be uninstalled. This action isn’t guaranteed

work,

but it is a common approach, as the

question suggests. Option A is incorrect because it will delete any other unrelated binaries, it will miss

any non-binary files

(such

man pages), and it might not even uninstall the binary, if it was installed in

non-standard

location. Option B will delete the source code directory, but unless the program was run

directly from that location (an unusual configuration), it won’t delete the installed binary program, so this

option is incorrect. Option C is incorrect because it’s a way to uninstall a package installed via the RPM

Package Manager (RPM), not from a source tarball.

15.

C. Tarballs are files archived with tar and, frequently, compressed with gzip or bzip2. They

usually have filenames that end in .tgz, .tar.gz, .tbz, .tbz2, or .tar.bz2. Only option C describes such

a file. Although the filename doesn’t contain a hint that it contains source code, this is not uncommon for

Unix and Linux source tarballs. Option A’s .pkg filename extension identifies it as a probable Mac OS X

binary package file, not a source tarball, so option A is incorrect. A .zip filename extension

identifies a PkZip archive. Although such files are comparable to tarballs in features,

they aren’t technically tarballs. These files are more commonly used in the Windows world,

so it’s likely that option B contains a Windows binary. Even if it contains source code, its non-tarball

nature means that this option is incorrect. Option D takes the form for a source RPM file. Although such

files contain source code, they aren’t source tarballs, as the question specifies, so option D is incorrect.

16.

B. Option B provides a correct, if simplified, description of how to install many source code packages.

Option A is likely to not build correctly, since the make install command

precedes ./configure. (It might work if the software includes no configure script, but most open

source software uses such a script.) Option C will result in

software

installation, since there is no call to

make install or other software installation commands. Option D might install the software, but the make

uninstall

command will immediately uninstall it.

17.

A. The --prefix option to a configure script usually sets the base of the installation directory

tree. In this example, binary files will probably go in /opt/bin, libraries in /opt/lib, and so on. The

--install, --dir, and --goto options are

all

fictitious.

18.

A, C. Copying the compiled program with cp, as in option A, will install the software, thus satisfying

the question; however, the ownership and permissions on the program

file

may

not be optimal. The

install program, used as in option C, changes ownership and permissions as the file is copied, so it is a

superior answer to the question—but both A and C remain correct. The rpm command in option B will

attempt to read theprog as an RPM file and install its contents; however, since theprog is a Linux binary

program file, this won’t work, and option B will fail. Option D won’t work because the question specified

that the Makefile does not include an install target, so typing make install (even with the additional

parameter theprog) will not work.

19.

C. The /etc/issue.net file contains text that’s sent by the Telnet server to the remote Telnet client

prior to Telnet’s sending the login: prompt—precisely what the question requires. There is no

standard /etc/profile.net configuration file, and /etc/profile is a configuration

file for the bash shell, which won’t

help

achieve

the question’s goals. The

/etc/issue file is similar to /etc/issue.net, but it controls the message that’s displayed on the local

text-mode console.

20.

A. The /etc/motd file holds the message of the day, which is displayed after users

log

in using

text-mode tools such as text-mode consoles or SSH. An empty /etc/motd file simply means that no

such message will appear, as option A describes. There is

such

thing as Morton’s Own

Temporary Documentation, referred to in

option

There is no standard

/etc/motd.conf file, as described in option C. Witty aphorisms are created by the fortune program,

which is usually called in ways that don’t involve /etc/motd. Although they might not be displayed,

as option D

suggests,

there’s

no linkage between this and the empty /etc/motd file;

fortunes are enabled or disabled in other ways.

Review

Questions

What is the conventional name for a locally compiled, bootable Linux kernel on an x86 system?

/boot/vmlinux-version

/boot/vmlinuz

/boot/bzImage-version

/usr/src/linux-version

Which of the following statements about /usr/src/linux is usually true?

It is a symbolic link to a directory holding the system’s current kernel source code, or the version

currently being prepared.

It holds subdirectories, each of which contains the source code for a different version of the Linux

kernel.

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