Which of the following commands will direct error messages to the file error log

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Which of the following commands will direct error messages to the file, error.log?. (choose one)

• ls /root > error.log
• ls /root >> error.log
• ls /root 2> error.log
• ls /root $> error.log

The echo command:

• Tests a variable for duplication
• Duplicates the input stream to the output stream
• Is used for variable assignment
• Is used to output text to the console
• Copies variables from one to another

Which are appropriate editors for writing shell scripts?. (choose two)

• nano
• LibreOffice Writer
• /bin/bash
• vi
• Firefox

64 bit platforms can access more memory than 32 bit platforms.. True or False?

• True
• False

What does the acronym RPM mean?

• Relocate Package Manager
• Return Package Management
• RPM Package Management
• Recursive Package Manager

One way to install new software on a Linux system is to use a package management system.. True or False?

• True
• False

When you execute the dmesg command, the system displays messages that are generated by the kernel.. True or False?

• True
• False

Which of the following are package management commands for distributions with software distributed in files ending in .deb?. (choose three)

• rpm
• apt-get
• dpkg
• aptitude

Which of the following are package management commands for distributions with software distributed in files ending in .rpm?. (choose three)

• yum
• apt-get
• rpm
• yumex

Which of the following would be considered a host?

• A printer attached to the network via an IP address
• A CDROM
• The computer’s hard drive
• A network cable

A network packet contains …. (choose two)

• …the IP address of the destination machine.
• …a hard drive partition.
• …the name of the router.
• …the IP address of the source machine.

Only servers have hostnames.. True or False?

• True
• False

Which files contain user account information?. (choose two)

• /etc/passwd
• /etc/shadow
• /etc/group

Which user can view the /etc/shadow file?

• The root user
• No users
• Any member of the password group
• All users

Which command will display the UID, GID and groups your current user belongs to?

• id
• whoami
• who
• about

Each user belongs to at least one group.. True or False?

• True
• False

Which command will display the users that are currently logged in to the system?

• who
• about
• whoami
• id

UIDs 1-500 are usually reserved for what kind of users?

• Are not used for user accounts, but for group accounts
• System accounts, such as server processes
• Remote log-in accounts
• Log-in (human) users

NDG Linux Essentials — CISCO Networking Academy — Questions and Answers 

Chapter 01

Chapter 02

CORRECT — See section 2.3.1

If you wanted to set up a blog,
which software would be most helpful?

• WordPress

CORRECT — See section 2.3.3

Which of the following are examples
of text editors?

• vim
• emacs
• pico
• nano

WRONG — See section 2.3.4

Which of the following are true
about compiled programming languages?

• Ruby is a compiled language

WRONG — See section 2.3.3

The Linux shell:

• Has a scripting language
• Is customizable
• Has a built in text editor

CORRECT — See section 2.3.2

Which application would you use to
edit and piece together sound files to make podcast?

• Audacity

CORRECT — See section 2.3.1

Which server software would you use
to create a company directory that you could search and authenticate against?

• OpenLDAP

CORRECT — See section 2.3.1

A Mail Transfer Agents primary
purpose is to:

• Deliver mail between servers

CORRECT — See section 2.4.1

The Free Software Foundation
believes that:

• Software should be free to share
• Software should be free to modify

WRONG — See section 2.4.3

What is the meaning of a public
domain license?

• The work was done by a government agency

WRONG — See section 2.4.1

Permissive free software licenses:

• Are not approved by the FSF
• Can allow software to be used inside closed source
  software
• Include the GPLv2 and BSD

Chapter 03

CORRECT — See section 3.3

Which of the following is true about
graphical mode?

• You access this mode by logging into a graphical
  display
• You have menus and tools to help you find what you are
  looking for
• After login, you are provided with a desktop

WRONG — See section 3.3

Which of the following is provided
by a graphical interface that isnt normally provided to a non graphical
interface?

• menus
• windows
• desktop
• shell

CORRECT — See section 3.3

A server is likely to be running in
graphical mode.

• False

CORRECT — See section 3.5

Virtualization means:

• A single host can be split up into multiple guests

CORRECT — See section 3.5

In virtualization, what are the host
and guest?

• The host is the machine that runs the virtual machines
• A guest is a virtual machine

CORRECT — See section 3.6

If you wanted to write a report that
was to be printed, you would probably use:

• LibreOffice

CORRECT — See section 3.7

If you want to store logins and
passwords for different websites in a secure manner, you could use:

• KeePassX

CORRECT — See section 3.7

You can configure your computer to
check for updates automatically.

• True

CORRECT — See section 3.7

Which of the following are
properties of a strong password?

• At least 10 characters long
• A mix of upper and lower case
• Includes symbols

CORRECT — See section 3.7

What can be done to prevent remote
people from running programs on your computer?

• Turn on a firewall
• use strong passwords on all user accounts

Chapter 04

CORRECT — See section 4.4

Select all the applications that
provide access to the Command Line Interface (CLI)?

• Terminal window
• Virtual Terminal

CORRECT — See section 4.11.1

A pair of double quotes ( » )
will prevent the shell from interpreting any metacharacter.

• False

CORRECT — See section 4.12.1

The semicolon «;» can be
used to separate multiple commands to be executed in order.

• True

CORRECT — See section 4.12.2

The double ampersand characters (
&& ) are used to separate commands to be executed conditionally, where
if the command to the left of the ampersands fails, then the command to the
right of the ampersands will be executed.

• False

CORRECT — See section 4.6

To be able to output messages to the
screen use the _______ command:

• echo

CORRECT — See section 4.5

To execute the same command as
previously executed five commands ago, you would type:

• !-5

CORRECT — See section 4.4.2

The shell program is what interprets
the commands you type into the terminal into instructions that the Linux
Operating System can execute.

• True

CORRECT — See section 4.4.4

Traditional UNIX command options
used a single dash, like -a; _______ command options use two dashes like —all.

• GNU

CORRECT — See section 4.4.4

The acronym GNU stands for:

• Gnu’s Not Unix

CORRECT — See section 4.11.3

What one character treats the
character that follows it as if it was surrounded by single quotes?

Chapter 05

WRONG — See section 5.5.1

What is the standard option to
provide a command line program to view its documentation?

CORRECT — See section 5.3.6

Commands typically executed by a
user are covered in what section of the manual?

• 1

CORRECT — See section 5.3.6

Section 5 of the manual pages
covers:

• File Formats

CORRECT — See section 5.3.2

In order to exit viewing a man page,
press:

• q

CORRECT — See section 5.3.2

Which option for the man
command should you use if you intend to send the output of the command to a
printer?

• -t

CORRECT — See section 5.3.2

What key should be used while
working in the man command if you want to go to the end of the document?

• G

CORRECT — See section 5.4.2

To get help while using the info
command press:

• h

CORRECT — See section 5.4.2

To exit the info command press:

• q

CORRECT — See section 5.4.2

To go to the end of an info page
press:

• END

CORRECT — See section 5.3.2

To move a page forward one at a time
while viewing a man page, press the following:

• Spacebar

Chapter 06

CORRECT — See section 6.3

The top-level directory on a Linux
system is represented as:

• /

CORRECT — See section 6.3.2

The tilde (~) is used to represent:

• A user’s home directory.

CORRECT — See section 6.3.2

Which of the following commands can
be used to access the home directory of the user «bob» while logged
in as root?

• cd /home/bob
• cd ~bob

WRONG — See section 6.3.5

The double dot (..) can be used to
represent the directory…

• …any directory below the current directory

CORRECT — See section 6.4

The ls command without options or
arguments…

• …lists the contents of the current directory.

CORRECT — See section 6.4.3

The first character in a long
listing (ls -l) indicates:

• If something is a file, directory, or symbolic link

CORRECT — See section 6.4.1

Which of the following commands will
prevent any aliased options to the ls command?

• ls

CORRECT — See section 6.5.2

Which option(s) can be used to
prevent cp from overwriting an existing file?

• -i
• -n

CORRECT — See section 6.7.1

Which of the following commands can
be used to rename a file?

• mv

CORRECT — See section 6.8

The touch command can be used to:

• create new files
• update the time stamp of existing files

Chapter 07

CORRECT — See section 7.3

You type gzip myfile.tar. What happens?

• myfile.tar is removed
• myfile.tar.gz holds a compressed version of myfile.tar

CORRECT — See section 7.4

Which flag would you pass to tar in
order to have it make a new archive?

• -c

CORRECT — See section 7.4

Which command will show whats inside
the compressed tarball with a name of foo.tar.gz?

• tar tzf foo.tar.gz

WRONG — See section 7.4

Given the command tar cvjf homedirs.tbz /home, which of the following are true?

• Files that are present in the archive might overwrite
  files in /home
• The /home directory will be restored with the contents
  of homedirs.tbz

CORRECT — See section 7.5

Which of the following commands will
create a zipfile with the contents of your Documents directory?

• zip -r mydocs.zip Documents

CORRECT — See section 7.5

Given a file called documents.zip,
how can you see whats in it without extracting the files?

• unzip l documents.zip

CORRECT — See section 7.3

You try to compress a file that is
already compressed. Which of the following statements is true?

• The file will not be compressed any further than it
  already was

WRONG — See section 7.4

The three main modes of tar
are:

• Create
• Extract

CORRECT — See section 7.4

Which two commands do the same
thing?

• tar c foo | gzip > foo.tar.gz
• tar czf foo.tar.gz foo

CORRECT — See section 7.1

The _____ command is normally
executed daily to update the database of all files that are on the system.

• updatedb

Chapter 08

CORRECT — See section 8.4.3

Error messages generated by commands
are sent where by default?

• STDERR

CORRECT — See section 8.4.2

A successful command will print
output to STDOUT.

• True

CORRECT — See section 8.3

A pipe allows you to…

• …send the output of one command to another

CORRECT — See section 8.11

The grep command can be used with
glob characters.

• True

CORRECT — See section 8.5

The find command can search for files based
on the size of the file.

• True

WRONG — See section 8.5

Which of the following commands
scans the file to determine file locations?

• locate

CORRECT — See section 8.10

Which option for the cut
command is used to specify a delimiter?

• -d

CORRECT — See section 8.10

Which option for the cut
command is used to specify the field?

• -f

CORRECT — See section 8.9

Which option for the wc
command will print the number of lines in a file?

• -l

CORRECT — See section 8.4.4

The command echo «text» > file.txt will not overwrite file.txt if it already exists.

• False

Chapter 09

CORRECT — See section 9.3

A file begins with #!/bin/csh. This means:

• Running the script will invoke /bin/csh to interpret
  the rest of the file

CORRECT — See section 9.4

Which are appropriate editors for
writing shell scripts?

• nano
• vi

WRONG — See section 9.4

Most of nanos commands take the form
of:

CORRECT — See section 9.5.2

What does this shell script do?

FOO=/tmp/foo

if
[ ! d $FOO ]; then

    mkdir $FOO

fi

• Creates /tmp/foo if it does not exist

CORRECT — See section 9.5.1

Given the following part of a
script:

if
[ -f $1 ]; then

    echo I am here

fi

What is the meaning of $1?

• It is the first argument passed to the script

CORRECT — See section 9.5.1

What information is held inside $?
?

• The previous commands exit code

CORRECT — See section 9.5.1

How would you finish your script
with an exit code of 42?

• exit 42

CORRECT — See section 9.5.2

The if command looks for what exit code to
consider a condition to be true?

• 0

WRONG — See section 9.5.2

Given the following script:

while
[ ! f /tmp/foo ]; do

    echo n .

    process_data > /tmp/foo

done

Which of the following are true?

• process_data will be called at most once

WRONG — See section 9.5.2

A conditional that lets you make
multiple comparisons with a pattern is called:

• if

Chapter 10

CORRECT — See section 10.3

Which of the following are valid CPU
types for Intel-based platforms?

• 32 bit
• 64 bit

CORRECT — See section 10.3

64 bit platforms can access more
memory than 32 bit platforms.

• True

WRONG — See section 10.3

Which of the following commands will
display CPU information?

• arch
• lspic
• cat /proc/cpuinfo

CORRECT — See section 10.3

A CPU flag…

• …defines the features that the CPU supports

CORRECT — See section 10.4

Which command displays information
from SMBIOS?

• dmidecode

CORRECT — See section 10.4.3

Which of the following are common
busing systems?

• USB
• PCI

CORRECT — See section 10.6

Which of the following are valid
partitioning types?

• MBR
• GPT

CORRECT — See section 10.6

The fdisk command is a tool used for working
with the MBR partitioned disks.

• True

WRONG — See section 10.6

Which of the following is the valid
device file name for the first IDE hard drive on the system?

• /dev/ide

CORRECT — See section 10.7

Which of the following are valid
video cable connector types?

• VGA
• DVI

Chapter 11

CORRECT — See section 11.3

One way to install new software on a
Linux system is to use a package management system.

• True

CORRECT — See section 11.10

When you execute the dmesg
command, the system displays messages that are generated by the kernel.

• True

CORRECT — See section 11.3.1

Which of the following are package
management commands for distributions with software distributed in files ending
in «.deb»?

• dpkg
• aptitude
• apt-get

WRONG — See section 11.3.2

Which of the following are package
management commands for distributions with software distributed in files ending
in «.rpm»?

• yum

WRONG — See section 11.4

The Linux kernel mounts the
following pseudo-filesystems to provide access to information about hardware
devices connected to the system:

• /info
• /proc

CORRECT — See section 11.4

The Process ID (PID) of the init
process is

• 1

WRONG — See section 11.8

The free command outputs statistics about:

• Disk usage

CORRECT — See section 11.9

What directory typically contains
log files?

• /var/log

CORRECT — See section 11.9

All log files contain only text
data.

• False

CORRECT — See section 11.4

Which file contains the information
passed to the kernel at boot time?

• /proc/cmdline

Chapter 12

WRONG — See section 12.3

Which of the following would be
considered a host?

• The computer’s hard drive

CORRECT — See section 12.3

A service is…

• …a feature provided by one computer to another

CORRECT — See section 12.5

A network packet contains …

• …the IP address of the destination machine
• …the IP address of the source machine

WRONG — See section 12.4

Which of the following protocols
defines how network communication functions?

• DHCP

CORRECT — See section 12.5

Which of the following are valid
IPv4 addresses?

• 192.105.10.10
• 10.33.55.77

CORRECT — See section 12.7.1

Which of the following commands will
display your machine’s IP address?

• ifconfig

WRONG — See section 12.7.2

Which of the following commands will
display the routing table?

• dig
• route

CORRECT — See section 12.7.4

What option to the netstat command has information shown as numbers rather than names?

• -n

CORRECT — See section 12.7.6

Which of the following commands will
allow you to log into the machine server1 with the account name nick?

• ssh nick@server1

CORRECT — See section 12.7.6.1

The RSA key fingerprint allows the
dig command to connect to remote systems.

• False

Chapter 13

WRONG — See section 13.3

Which files contain user account
information?

• /etc/shadow
• /etc/group

CORRECT — See section 13.3.4

Which command will display the UID,
GID and groups your current user belongs to?

• id

CORRECT — See section 13.8

Which command will display the users
that are currently logged in to the system?

• who

WRONG — See section 13.7.1

The sudo command allows regular users to…

WRONG — See section 13.6

Which of the following commands will
allow you to switch to the user «branch»?

• su branch
• sudo branch

CORRECT — See section 13.7.1

The visudo command uses which text editor by
default?

• vi

CORRECT — See section 13.4

A user can belong to…

• At least 16 groups

CORRECT — See section 13.7.1

Sudo privileges can be used to
specify which user can use the sudo command to execute commands as other users.

• True

CORRECT — See section 13.7.1

In distributions that do not allow
the root user to login directly or via the su command, the installation process
automatically configures one user account to be able to use the sudo
command to execute commands as if they were executed by the root user.

• True

CORRECT — See section 13.3.3

Which command can be used to view
the /etc/passwd file entries?

• getent

Chapter 14

CORRECT — See section 14.8.1

On a system that does not use UPG,
the useradd command will also create a user group. For example, user
«bob», group «bob».

• False

CORRECT — See section 14.12.1

The usermod command
can be used to do all of the following except…

• …change the user’s MAX and MIN password settings

CORRECT — See section 14.12.1

Which of the following commands will
add the group «extra» to the user bob’s secondary groups in addition
to bob’s current secondary groups?

• usermod -aG extra bob

CORRECT — See section 14.12.1

Which option for the usermod command can be used to specify a user’s group ID (either
primary or secondary)?

• -g
• -G

CORRECT — See section 14.13

The userdel command
will…

• delete the user account, but leave the user’s files by
  default

CORRECT — See section 14.4

The groupmod command
can be used to change a group name.

• True

CORRECT — See section 14.4

The groupmod command
can be used to add users to a group

• False

CORRECT — See section 13.3.4

Which of the following commands can
be used to modify a group?

• groupmod

CORRECT — See section 14.12

Which command can be used to
determine a user’s most recent log in?

• last

CORRECT — See section 14.12.1

Which of the following commands, run
as root, will prevent the user «bob» from logging in?

• usermod -L bob

Chapter 15

CORRECT — See section 15.7.2

Only one set (user, group, other) of
permission can be changed at once using the symbolic method.

• False

CORRECT — See section 15.7.2

Which of the following are methods
for setting permissions using the chmod command?

• octal
• symbolic

WRONG — See section 15.7.2

The user «sysadmin» will
be able to change the permissions of the «file» because they own it.

—-r—r—  1 
sysadmin  group  38270 
Sep 2 18:49  file

• False

CORRECT — See section 15.7.3

Octal notation uses the following
values for the permissions granted:

• r = 4, w = 2, x = 1

CORRECT — See section 15.7

Which of the following permissions
would allow all users to add, view, and delete files in a directory?

• 777

CORRECT — See section 15.7

A user cannot delete a file if they
do not own it.

• False

CORRECT — See section 15.7

The «execute» permission
on a file allows you to:

• Run the file as a script

WRONG — See section 15.6

The chmod command can be used on a file by:

• Only root

CORRECT — See section 15.9

The «execute» permission
is never set on files by default.

• True

CORRECT — See section 15.7

The user owner of a file will always
have the same or higher permissions as «other».

• False

Chapter 16

CORRECT — See section 16.9

The /tmp directory is a temporary
directory and will not exist on a system at all times.

• False

WRONG — See section 16.7

The «sticky bit»
permission…

• prevents others from overwriting files they don’t own
  in common directories

CORRECT — See section 16.7

Which of the following commands will
set the «sticky bit» on /shared ?

• chmod 1777 /shared

CORRECT — See section 16.3

Which of the following commands will
set setuid for /usr/bin/program?

• chmod 4755 /usr/bin/program

WRONG — See section 16.4

The setgid permission…

• allows a command to be run as the group owner of the file.

WRONG — See section 16.5

Setting setgid on a directory…

• does nothing

CORRECT — See section 16.8.3

Deleting a source file will break an
associated hard link.

• False

CORRECT — See section 16.8.3

A source and a hard link must be
part of the same filesystem.

• True

CORRECT — See section 16.8.3

Deleting a source file will break an
associated symbolic link.

• True

CORRECT — See section 16.8.3

A source file and a symbolic link
must be part of the same file system.

• False

Final Comprehensive Exam

CORRECT — See section 1.3.1

One of the jobs of the kernel is to:

• Manage the systems resources

CORRECT — See section 1.3.3

Source code refers to:

• A human readable version of computer software

CORRECT — See section 5.5.1

What is the standard option to
provide a command line program to view its documentation?

• —help

CORRECT — See section 5.3.7

The command man -k
is the same as the command apropos.

• True

CORRECT — See section 5.3.6.3

The whatis command is the same as man -w.

• False

CORRECT — See section 6.4.2

Hidden files are files that begin
with what character?

• A period (.)

CORRECT — See section 6.4.2

What option for the ls
command will display all files, including hidden files?

• -a

CORRECT — See section 6.3

The top-level directory on a Linux
system is represented as:

• /

CORRECT — See section 6.3.5

Is the following path absolute or
relative?

/etc/ppp

• Absolute

CORRECT — See section 6.3.5

Is the following path absolute or
relative?

sysadmin/Documents

• Relative

CORRECT — See section 7.1

Compression on a file works by:

• Removing redundant information

CORRECT — See section 7.3

Lossy compression:

• Usually results better compression than lossless
• Is often used with images
• Sacrifices some quality

CORRECT — See section 7.3

You type gzip myfile.tar. What happens?

• myfile.tar is removed
• myfile.tar.gz holds a compressed version of myfile.tar

CORRECT — See section 8.4.2

A successful command will print
output to STDOUT.

• True

CORRECT — See section 8.4.5

Which of the following commands will
direct error messages to the file, error.log?

• ls /root 2> error.log
• ls /root &> error.log

CORRECT — See section 8.3

A pipe allows you to…

• …send the output of one command to another.

CORRECT — See section 8.4.5

Channel 2 is:

• STDERR

CORRECT — See section 9.3

The echo command:

• Is used to output text to the console

CORRECT — See section 9.3

A file begins with #!/bin/csh. This means:

• Running the script will invoke /bin/csh to interpret
  the rest of the file

CORRECT — See section 9.4

Most of nanos commands take the form
of:

• Control and another character

CORRECT — See section 10.3

64 bit platforms can access more
memory than 32 bit platforms.

• True

CORRECT — See section 11.3

One way to install new software on a
Linux system is to use a package management system.

• True

CORRECT — See section 11.10

When you execute the dmesg
command, the system displays messages that are generated by the kernel.

• True

CORRECT — See section 11.3.1

Which of the following are package
management commands for distributions with software distributed in files ending
in .deb?

• dpkg
• aptitude
• apt-get

CORRECT — See section 12.3

Which of the following would be
considered a host?

• A printer attached to the network via an IP address

CORRECT — See section 12.3

A service is…

• …a feature provided by one computer to another.

CORRECT — See section 12.4

Only servers have hostnames.

• False

CORRECT — See section 13.3.2

Which user can view the /etc/shadow
file?

• The root user

CORRECT — See section 13.1

Each user belongs to at least one
group.

• True

CORRECT — See section 13.8

Which command will display the users
that are currently logged in to the system?

• who

CORRECT — See section 14.8.1

UIDs 1-500 are usually reserved for
what kind of users?

• System accounts, such as server processes

CORRECT — See section 14.13

If a user is deleted, the files and
directories that the user owned…

• …will show a UID as the owner, but not user name.

CORRECT — See section 14.8.1

Which of the following options for
the useradd command allows root to specify the UID to be associated
with the account?

• -u

CORRECT — See section 14.8.1

Which of the following options for
the useradd command allows root to specify supplementary groups the
user will be a member of?

• -G

CORRECT — See section 15.7.2

Which of the following commands set
«other» permissions on file to r-x?

• chmod o=rx file

CORRECT — See section 15.7.2

Which of the following are methods
for setting permissions using the chmod command?

• octal
• symbolic

CORRECT — See section 2.3.1

If you wanted to set up a blog,
which software would be most helpful?

• WordPress

CORRECT — See section 2.3.1

Which of the following pieces of
software deal with file sharing?

• Samba
• Netatalk
• NFS

CORRECT — See section 2.3.2

If you wanted to create and print an
invoice, which software could you use?

• LibreOffice

CORRECT — See section 3.3

Which of the following is true about
graphical mode?

• You access this mode by logging into a graphical
  display
• You have menus and tools to help you find what you are
  looking for
• After login, you are provided with a desktop

CORRECT — See section 3.3

A server is likely to be running in
graphical mode.

• False

CORRECT — See section 3.5

Which of the following are traits of
a multiuser operating system?

• Many users can log in simultaneously with a unique
  account
• Users can protect their information from other users
• Resources are shared between users

CORRECT — See section 4.4

Select all the applications that
provide access to the Command Line Interface (CLI)?

• Terminal window
• Virtual Terminal

WRONG — See section 4.8

Select the command that can report
the location of a command:

• where

CORRECT — See section 4.11.2

A pair of single quotes ( ‘ ) will
prevent the shell from interpreting any metacharacter.

• True

CORRECT — See section 16.9

The /tmp directory is a temporary
directory and will not exist on a system at all times.

• False

CORRECT — See section 16.9

The /var directory has files that
change over time.

• True

WRONG — See section 16.7

The «sticky bit»
permission…

CORRECT — See section 16.7

Which of the following commands will
set the «sticky bit» on /shared ?

• chmod 1777 /shared

CORRECT — See section 16.3

The «setuid» permission…

• …allows a command to be run as the file owner.

At the time of writing, the Apache HTTP server is
used by 30.8% of all web
servers in operation. If you’re responsible for managing any system that
utilizes Apache, then you will surely interact with its logging infrastructure
on a regular basis. This tutorial will introduce you to logging in Apache and
how it can help you diagnose, troubleshoot, and quickly resolve any problem you
may encounter on your server.

You will learn where logs are stored, how to access them, and how to customize
the log output and location to fit your needs. You will also learn how to
centralize Apache logs in a log management system for easier tracing, searching,
and filtering of logs across your entire stack.

Prerequisites

To follow through with this tutorial, you should set up a Linux server that
includes a non-root user with sudo privileges. Additionally, you also need the
Apache HTTP server installed and enabled on the server, which can be done by
executing the relevant commands below.

On Debian-based distributions like Ubuntu:

sudo systemctl enable apache2

sudo systemctl start apache2

On RHEL, Fedora or CentOS:

sudo systemctl enable httpd

sudo systemctl start httpd

Please note that the rest of the commands, directory configurations, and
conventions used in this tutorial pertain to Debian-based distributions like
Ubuntu. Still, the concepts remain the same for other distributions.

Step 1 — Getting started with Apache logging

Apache logs are files that record everything the Apache web server is doing for
later analysis by the server administrator. The records of all Apache events are
placed in two different text files:

• Access Log: this file stores information about incoming requests. You’ll
  find details about each request such as the requested resource, response
  codes, time taken to generate the response, IP address of the client, and
  more.
• Error Log: this file contains diagnostic information about any errors were
  encountered while processing requests.

Step 2 — Locating the Apache log files

The log files’ location depends on the operating system the Apache web server is
running. On Debian-based operating systems like Ubuntu, the access log file is
located in /var/log/apache2/access.log. On CentOS, RHEL, or Fedora, the access
log file is stored in /var/log/httpd/access_log.

A typical access log entry might look like this:

::1 - - [13/Nov/2020:11:32:22 +0100] "GET / HTTP/1.1" 200 327 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.198 Safari/537.36"

Similarly, the error log file is located in /var/log/apache2/error.log on
Debian-based systems and /var/log/httpd/error_log on CentOS, RHEL, or Fedora.
A typical error log entry might look like this:

[Thu May 06 12:03:28.470305 2021] [php7:error] [pid 731] [client ::1:51092] script '/var/www/html/missing.php' not found or unable to stat

In the next section, we’ll discuss how to view these log files from the command
line.

Step 3 — Viewing Apache Log files

One of the most common ways to view an Apache log file is through the tail
command which prints the last 10 lines from a file. When the -f option is
supplied, the command will watch the file and output its contents in real-time.

sudo tail -f /var/log/apache2/access.log

You should observe the following output on the screen:

. . .

198.54.132.137 - - [04/Feb/2022:11:34:04 +0000] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:04 +0000] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:04 +0000] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:05 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:06 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:06 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:07 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:07 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"

To view the entire contents of the file, you can use the cat command or open
the file in a text editor like nano or vim:

cat /var/log/apache2/access.log

You may also want to filter the log entries in the log file by a specific term.
In such cases, you should use the grep command. The first argument to grep
is the term you want to search for, while the second is the log file that will
be searched. In example below, we are filtering all the lines that contain the
word GET:

sudo grep GET /var/log/apache2/access.log

This should present the following output:

. . .

198.54.132.137 - - [04/Feb/2022:11:34:04 +0000] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:04 +0000] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:05 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:06 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:06 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:07 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"
198.54.132.137 - - [04/Feb/2022:11:34:07 +0000] "GET / HTTP/1.1" 200 3476 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/97.0.4692.99 Safari/537.36"

Step 4 — Examining Apache access log formats

The access log records all requests that are processed by the server. You can
see what resources are being requested, the status of each request, and how long
it took to process their response. In this section, we’ll dive deeper into how
to customize the information that is displayed in this file.

Before you can derive value from reading a log file, you need to understand the
format that is being used for each of its entries. The CustomLog directive is
what controls the location and format of the Apache access log file. This
directive can be placed in the server configuration file
(/etc/apache2/apache2.conf) or in your virtual host entry. Note that defining
the same CustomLog directive in both files may cause problems.

Let’s look at the common formats used in Apache access logs and what they mean.

Common Log Format

The Common Log Format
is the standardized access log format format used by many web servers because it
is easy to read and understand. It is defined in the /etc/apache2/apache2.conf
configuration file through the LogFormat directive.

When you run the command below:

sudo grep common /etc/apache2/apache2.conf

You will observe the following output:

LogFormat "%h %l %u %t "%r" %>s %O" common

The line above defines the nickname common and associates it with a particular
log format string. A log entry produced by this format will look like this:

127.0.0.1 alice Alice [06/May/2021:11:26:42 +0200] "GET / HTTP/1.1" 200 3477

Here’s an explanation of the information contained in the log message above:

• %h -> 127.0.0.1: the hostname or IP address of the client that made the
  request.
• %l -> alice: remote log name (name used to log in a user). A placeholder
  value (-) will be used if it is not set.
• %u -> Alice: remote username (username of logged-in user). A placeholder
  value (-) will be used if it is not set.
• %t -> [06/May/2021:11:26:42 +0200]: the day and time of the request.
• "%r" -> "GET / HTTP/1.1" — the request method, route, and protocol.
• %>s -> 200 — the response code.
• %O -> 3477 — the size of the response in bytes.

Combined Log Format

The Combined Log Format
is very similar to the Common log format but contains few extra pieces of
information.

It’s also defined in the /etc/apache2/apache2.conf configuration file:

sudo grep -w combined /etc/apache2/apache2.conf

You will observe the following output:

LogFormat "%h %l %u %t "%r" %>s %O "%{Referer}i" "%{User-Agent}i"" combined

Notice that it is exactly the same as the Common Log Format, with the addition
of two extra fields. Entries produced in this format will look like this:

127.0.0.1 alice Alice [06/May/2021:11:18:36 +0200] "GET / HTTP/1.1" 200 3477 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36"

Here’s an explanation of the two additional fields that are not present in the
Common log format:

• "%{Referer}i" -> "-": the URL of the referrer (if available, otherwise
  - is used).
• "%{User-Agent}i" ->
  "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/90.0.4430.93 Safari/537.36":
  detailed information about the user agent of the client that made the request.

Step 5 — Creating a custom log format

You can define a custom log format in the /etc/apache2/apache2.conf file by
using the LogFormat directive followed by the actual format of the output and
a nickname that will be used as an identifier for the format. After defining the
custom format, you’ll pass its nickname to the CustomLog directive and restart
the apache2 service.

In this example, we will create a log format named custom that looks like
this:

LogFormat "%t %H %m %U %q %I %>s %O %{ms}T" custom

Open your /etc/apache2/apache2.conf file and place the line above below the
other LogFormat lines. It will produce access log entries with the following
details:

• %t: date and time of the request.
• %H: the request protocol.
• %m: the request method.
• %U: the URL path requested.
• %q: query parameters (if any).
• %I: total bytes received including the request headers.
• %>s: final HTTP status code.
• %O: number of bytes sent in the response.
• %{ms}T: time taken to generate the response in milliseconds.

You can find all other formatting options and their description on
this page.

To enable the custom format for subsequent access log entries, you must change
the value of the CustomLog directive in your virtual hosts file and restart
the apache2 service with Systemctl.

Open up the default virtual hosts file using the command below:

sudo nano /etc/apache2/sites-available/000-default.conf

Find the following line:

CustomLog ${APACHE_LOG_DIR}/access.log combined

And change it to:

CustomLog ${APACHE_LOG_DIR}/access.log combined

Save the file by pressing Ctrl-O then Ctrl-X, then restart the apache2
service using the command below:

sudo systemctl restart apache2

Afterward, make the following request to your server using curl:

curl --head 'http://<your_server_ip>?name=john&age=30'

You should observe the following response:

HTTP/1.1 200 OK
Date: Mon, 07 Feb 2022 14:21:45 GMT
Server: Apache/2.4.41 (Ubuntu)
Last-Modified: Mon, 07 Feb 2022 12:57:29 GMT
ETag: "2aa6-5d76d24a738bc"
Accept-Ranges: bytes
Content-Length: 10918
Vary: Accept-Encoding
Content-Type: text/html

Go ahead and view the last 10 messages in the access log file:

sudo tail /var/log/apache2/access.log

The log entry that describes the request will look like this:

[07/Feb/2022:14:21:45 +0000] HTTP/1.1 HEAD /index.html ?name=john&age=30 96 200 255 0

It’s also possible to create multiple access log files by specifying the
CustomLog directive more than once. In the example below, the first line logs
into a custom.log file using the custom log format, while the second uses
the common format to write entries into access.log. Similarly, the
combined.log file contains messages formatted according to the combined log
format.

CustomLog ${APACHE_LOG_DIR}/custom.log custom
CustomLog ${APACHE_LOG_DIR}/access.log common
CustomLog ${APACHE_LOG_DIR}/combined.log combined

Step 6 — Formatting your logs as JSON

Although many log management systems support the default Apache logging formats,
it might be best to log in a structured format like JSON since that’s the go-to
format for structured logging in the industry and it is universally supported.
Here’s a conversion of our custom log format into JSON:

LogFormat "{ "timestamp":"%t", "protocol":"%H", "method":"%m", "request":"%U", "query":"%q", "request_size_in_bytes":"%I", "status_code":"%>s", "response_size_in_bytes":"%O", "time_taken_ms":"%{ms}T" }" json

This produces log entries with the following formatting:

{
  "timestamp": "[07/Feb/2022:15:09:02 +0000]",
  "protocol": "HTTP/1.1",
  "method": "HEAD",
  "request": "/index.html",
  "query": "?name=john&age=30",
  "request_size_in_bytes": "96",
  "status_code": "200",
  "response_size_in_bytes": "255",
  "time_taken_ms": "0"
}

Step 7 — Configuring Apache error logs

The server error log contains information about any errors that the web server
encountered while processing incoming requests as well as other diagnostic
information. You can choose where the error messages will be transported to
using the ErrorLog directive in your virtual host configuration file. This
transport is usually a log file on the filesystem.

Here is an example from default virtual host configuration file
/etc/apache2/sites-available/000-default.conf:

ErrorLog ${APACHE_LOG_DIR}/error.log

On Debian-based distributions, the default error log is in the
/var/log/apache2/error.log file, while in Fedora/CentOS/RHEL, it placed in the
/var/log/httpd/error_log file. If the path argument to ErrorLog is not
absolute, then it is assumed to be relative to the
ServerRoot.

A common practice is to monitor the error log continuously for any problems
during development or testing. This is easily achieved through the tail
command:

sudo tail -f /var/log/apache2/error.log

You will observe the following output:

[Mon Feb 07 13:03:43.445444 2022] [core:notice] [pid 10469:tid 140561300880448] AH00094: Command line: '/usr/sbin/apache2'
[Mon Feb 07 13:07:31.528850 2022] [mpm_event:notice] [pid 10469:tid 140561300880448] AH00491: caught SIGTERM, shutting down
[Mon Feb 07 13:07:31.626878 2022] [mpm_event:notice] [pid 10864:tid 140224997284928] AH00489: Apache/2.4.41 (Ubuntu) configured -- resuming normal operations
[Mon Feb 07 13:07:31.626980 2022] [core:notice] [pid 10864:tid 140224997284928] AH00094: Command line: '/usr/sbin/apache2'
[Mon Feb 07 13:13:25.966501 2022] [mpm_event:notice] [pid 10864:tid 140224997284928] AH00491: caught SIGTERM, shutting down
[Mon Feb 07 13:13:26.049222 2022] [mpm_event:notice] [pid 11268:tid 139760377875520] AH00489: Apache/2.4.41 (Ubuntu) configured -- resuming normal operations
[Mon Feb 07 13:13:26.049318 2022] [core:notice] [pid 11268:tid 139760377875520] AH00094: Command line: '/usr/sbin/apache2'
[Mon Feb 07 15:08:50.856388 2022] [mpm_event:notice] [pid 11268:tid 139760377875520] AH00491: caught SIGTERM, shutting down
[Mon Feb 07 15:08:50.940561 2022] [mpm_event:notice] [pid 12096:tid 140473452194880] AH00489: Apache/2.4.41 (Ubuntu) configured -- resuming normal operations
[Mon Feb 07 15:08:50.940669 2022] [core:notice] [pid 12096:tid 140473452194880] AH00094: Command line: '/usr/sbin/apache2'

Aside from logging directly to a file, you can also forward your logs to a
Syslog. You can do this by
specifying syslog
instead of a file path as the argument to ErrorLog:

Step 8 — Customizing the error log format

Like the Apache access logs, the format of the error messages can be controlled
through the ErrorLogFormat directive, which should be placed in the main
config file or virtual host entry. It looks like this:

ErrorLogFormat "[%{u}t] [%l] [pid %P:tid %T] [client %a] %M"

The above configuration produces a log entry in the following format:

[Mon Feb 07 15:52:57.234792 2022] [error] [pid 24372:tid 24507] [client 20.113.27.135:34579] AH01276: Cannot serve directory /var/www/html/: No matching DirectoryIndex (index.html) found, and server-generated directory index forbidden by Options directive

Here’s an explanation of the formatting options used above:

%{u}t: the current time, including microseconds. %l: the log level of the
message. %P: the process identifier. %T: the thread identifier. %a: the
client IP address. %M: the actual log message.

Note that when the data for a formatting option is not available in a particular
event, it will be omitted from the log entirely as the Apache error log doesn’t
use placeholder values for missing parameters.

You can find a complete description of all the available error formatting
options in the
Apache docs.

Step 9 — Customizing the error log level

In the virtual host configuration file, you can also control the level of
messages that will be entered into the error log through the
LogLevel directive.
When you specify a particular value, messages from all other levels of higher
severity will be logged as well. For example, when LogLevel error is
specified, messages with a severity of crit, alert, and emerg will also be
logged.

These are the levels available in increasing order of severity:

• trace1 — trace8: trace messages (lowest severity).
• debug: messages used for debugging.
• info: informational messages.
• notice: normal but significant conditions.
• warn: warnings.
• error: error conditions that doesn’t necessarily require immediate action.
• crit: critical conditions that requires prompt action.
• alert: errors that require immediate action.
• emerg: system is unusable.

If the LogLevel directive is not set, the server will set the log level to
warn by default.

Step 10 — Centralizing your Apache logs

Storing your Apache logs on the filesystem may suffice for development
environments or single-server deployments, but when multiple servers are
involved, it may be more convenient to centralize all your logs in a single
location so that you can automatically parse, filter, and search log data from
all sources in real-time.

In this section, we’ll demonstrate how you can centralize your Apache logs in a
log management service through Vector,
a high-performance tool for building observability pipelines. The following
instructions assume that you’ve signed up for a free
Logtail account and retrieved your source
token.

Go ahead and follow the relevant
installation instructions for Vector
for your operating system. On Ubuntu, you may run the following commands to
install the Vector CLI:

curl -1sLf  'https://repositories.timber.io/public/vector/cfg/setup/bash.deb.sh'  | sudo -E bash

After Vector is installed, confirm that it is up and running through
systemctl:

You should observe that it is active and running:

● vector.service - Vector
     Loaded: loaded (/lib/systemd/system/vector.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2022-02-08 10:52:59 UTC; 48s ago
       Docs: https://vector.dev
    Process: 18586 ExecStartPre=/usr/bin/vector validate (code=exited, status=0/SUCCESS)
   Main PID: 18599 (vector)
      Tasks: 3 (limit: 2275)
     Memory: 6.8M
     CGroup: /system.slice/vector.service
             └─18599 /usr/bin/vector

Otherwise, go ahead and start it with the command below.

sudo systemctl start vector

Afterwards, change into a root shell and append your Logtail vector
configuration for Apache into the /etc/vector/vector.toml file using the
command below. Don’t forget to replace the <your_logtail_source_token>
placeholder below with your source token.

wget -O ->> /etc/vector/vector.toml 
    https://logtail.com/vector-toml/apache2/<your_logtail_source_token>

Then restart the vector service:

sudo systemctl restart vector

You will observe that your Apache logs will start coming through in Logtail:

Conclusion

In this tutorial, you learned about the different types of logs that the Apache
web server stores, where you can find those logs, and how to view their
contents. We also discussed Apache access and error log formatting and how to
create your custom log formats, including a structured JSON format. Finally, we
considered how you can manage all your Apache logs in one place by using the
Vector CLI to stream each entry to a log management service.

Don’t forget to read the docs to
find out more about all the logging features that Apache has to offer. Thanks
for reading!

Next article

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