Chapter 4 - Managing Files Flashcards by Jon-Paul Brune

A few characters have special meaning and should never be used in filename. There are 5 of them:

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Asterisk
Question mark
Forward slash
Backslash
Quotation mark

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What is the limit on filename length?

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255 characters (255 bytes)

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Talking about dots and directories. If your current directory is /home/jerry, what does “.” And “..” refer to?

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. = /home/jerry (current directory)
.. = /home (parent directory)

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What is a wildcard?

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Symbol or set of symbols that stands in for other characters

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What are the 3 classes of wildcards?

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Question mark – single character
Asterisk – matches any character, set of characters, no character
Bracketed values – these characters match any characters in the set

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When you are understanding file commands, there are 5 everyday commands that are CRITICAL. Tell me what they are:

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List
Copy
Move
Rename
Delete

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Tell me the syntax for the list command

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ls [options] [files]

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if you do the ls command as ls –a or ls –all, what will happen?

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You’ll see the configuration files (begin with a .)

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If you do the ls command as ls –r or ls –recursive, what will happen?

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You’ll display the target directory’s files AND all of its subdirectories.

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Tell me the syntax for the copy command.

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cp [options] source destination

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if you do a cp –R, what will happen?

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You’ll copy the directory and all its subdirectories

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What is the syntax for the move command?

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mv [options] source destination

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what’s the command for deleting a file? What’s the syntax for it?

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rm [options] files

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in linux, there are 3 time stamps for every file. Tell me what they are:

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Last file-modification time
Last inode change time
Last access time

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What does the “make” utility do?

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Compiles a program from source code

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What do you use the “touch” command for?

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Modifying the time stamps

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There are several commands you can use for archiving files. Tell me what they are.

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tar
cpio
dd

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the tar utility has 7 commands you should know. What are they and what do they do?

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Create – c – creates an archive
Concatenate – A – appends tar files to an archive
Append – r – appends non tar files to an archive
Update – u – appends files that are newer than those in an archive
Diff (or compare) – d – compares an archive to files on disk
List – t – lists an archive’s contents
Extract (or get) – x – extracts files from an archive

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What do qualifiers do?

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They modify what commands do.

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What are the 6 most useful qualifiers and what do they do?

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g – perform incremental backup
p – keep permissions
z – use gzip compression
j – use bzip2 compression
J – use xz compression
v – be verbose

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there are 3 compression tools used with the tar command. Tell me what they are and whether they apply compression to the archive file or to the individual files of the archive file.

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gzip
bzip2
xz

They apply compression to the whole archive file.

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Of the 3 compression tools, which one offers the best compression? What is something that is compressed by it?

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The linux kernel

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Tell me the syntax for tar archiving.

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tar [options] destination/tar_file_name files-to-archive

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if you use the tar command to archive data, what command do you use to restore data from archive file or media device?

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cpio

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the cpio utility has 3 modes. Tell me what they are. 4-191,192

Copy out mode –o, this creates an archive and copies files into it Copy in mode –i, this extracts data from an existing archive Copy-pass mode –p, it combines the copy-out and copy-in

There are options for use with cpio. They are listed below, tell me their abbreviations and what they do. 1. Reset-access-time 2. Append 3. Pattern-file=filename 4. File=filename 5. Format=format 6. No-absolute-file-names 7. List 8. Unconditional 9. Verbose 4-192,193

1. Resets the access time after reading a file so that it doesn’t appear to have been read 2. Appends data to an existing archive 3. Uses the contents of filename as a list of files to be extracted in copy-in mode 4. Uses filename as the cpio archive file; if this parameter is omitted, cpio uses standard input or output 5. Uses a specified format for the archive file (bin, crc, and tar) 6. uses the filename specified by filename instead of standard output 7. desplays a table of contents for the input 8. replaces all files without first asking for verification 9. displays filenames as they’re added to or extracted from the archive

What do you have to do in order to use cpio to archive a directory? 4-193

You have to pipe the standard output of the find utility into the cpio command.

In linux, what is a link? 4-195

It is a way to give a file multiple identities.

What are the two types of links? 4-195

Hard links and symbolic links. Hard links are produced by creating two directory entries that point to the same file. The only difference is that one of the filenames was created before the other. Symbolic links are special file types, they are separate files whose contents point to the linked-to file.

Show me the difference in creating hard and symbolic links via commands. 4-196,197

ln afile.txt hlink_afile | ln –s bfile.txt slink_bfile

what does the mkdir command do? 4-198

Creates a directory

What does the rmdir command do? 4-198

Destroys a directory

You want to use the ls command to show ownership and permission information. How do you modify the command? 4-199

ls –l

which command allows you to change a file’s owner? 4-200

chown

which command allows you to change a file’s group? 4-200

chgrp

for a file, there are special bits called permission bits. For example, when you do ls –l test, the first part of the returned message is –rwxr-xr-x. the first character has special meaning. What does that first character tell you? 4-201

The file type code

There are 7 file type codes which are part of the access control string when the –l option is used on ls. Tell me what they are. ``` - d l p s b c ``` 4-201

``` normal data file directory symbolic link named pipe socket block device character device ```

how many bits does it take to represent the main linux permission options? 4-202

Tell me the breakdown of the access control string (what are the 10 bits for?) 4-202

1st bit – file type code 2nd, 3rd, 4th bits – owner permissions 5th, 6th, 7th bits – group permissions 8th, 9th, 10th bits – world permissions

The sum of bits adds up to a permission. What is read worth? What is write worth? What is execute worth? 4-203

Read – 4 Write – 2 Execute – 1

What is the sticky bit used for? 4-205

To protect files from being deleted by those who don’t own the files

When you change a file’s mode, what are you changing? What command allows you to do this? 4-206

Its permissions | chmod

you can specify a file’s mode in two basic forms. What are they? 4-206

Three digital octal | Symbolic

There are codes used in symbolic mode. These include the permission set code, the change type mode, and the permission to modify code. I’ll give you the name, you tell me what they mean. Permission set codes: u, g, o, a Change type codes: +, -, = Permission to modify codes: r, w, x, X, s, t, u, g, o 4-207

u- owner, g- group, o- other, a- All +- Add, -- Remove, =- set equal to r- read, w- write, x- execute, X- execute only if the file is a directory or already has execute permission, s- SUID or SGID, t- sticky bit, u- existing owner’s permissions, g- existing group permissions, o- existing other permissions

when you are setting the default mode and group, you subtract the umask from the directory permissions and file permissions. These permissions start at some number by default, what are they? 4-210

File permissions – 666 | Directory permissions – 777

What are disk quotas? 4-213

Limits enforced by the OS on how many files or how much space a single user may consume.

If you are the superuser, you can turn quotas on at any time. What command do you use for this? What about for turning them off? 4-214

quotaon, quotaoff

Say that you wanted to edit sally’s quota. What command do you use? What about for a whole group? 4-215,216

edquota sally | edquota –g users

FSSTND had limitations that were becoming more and more troublesome by 1995. What new standard replaced FSSTND? What does the acronym stand for? 4-217

FHS | Filesystem Hierarchy Standard

I’m going to through some directories at you. You tell me if they are static, variable, shareable, unshareable. ``` /usr /opt /etc /boot /home /var/mail /var/ru /var/lock ``` 4-218

/usr and /opt are static and shareable /etc and /boot are static and unshareable /home and /var/mail are variable and shareable /var/run and /var/lock are variable and unshareable

What does / mean? 4-218

The root directory, the root filesystem.

What does /boot have? 4-218

Static and unshareable files related to the computer’s initial booting.

What does /etc have? 4-218

Higher level startup files and system configuration files that control the various programs and services offered on a system.

What is /bin for? 4-219

This directory contains critical executable files (like ls, cp and mount).

What is /sbin for? 4-219

Similar to /bin, but it contains programs that are normally run only by the system administrator.

What is /lib for? 4-219

Similar to /bin and /sbin, but it contains program libraries.

What is /usr for? 4-219

Hosts the bulk of a linux computer’s programs.

What is /usr/local for? 4-219

Contains files that a system administrator installs locally.

What is /usr/share/man for? 4-219

Stores the manual pages used by the man command.

What is /usr/X11R6? 4-219

Houses files related to the X Window System.

What is /opt for? 4-219

Similar to /usr/local, but intended for ready-made packages that don’t ship with the OS.

What is /home for? 4-220

Contains users’ data

What is /root for? 4-220

Home directory for the root user.

What is /var for? 4-220

Contains transient files of various types (system log files, print spool files, mail and news files

What is /tmp for? 4-220

When programs need to create temporary files, they can be found here.

What is /mnt for? 4-220

Mounting removable media devices within its normal directory structure.

What is /media for? 4-220

Optional part of the FHS, contains subdirectories for specific media types.

What is /dev for? 4-220

Files that function as hardware interfaces

What is /proc for? 4-221

Virtual filesystem that is created dynalically to provide access to certain types of hardware information that aren’t accessible via /dev.

It is recommended to keep certain directories on their own partition. There are 7 of them. Tell me what they are. 4-221

``` /boot /home /opt /tmp /usr /usr/local /var ```

There are directories that should NOT be on their own partition. There are 5 of them. Tell me what they are. 4-221

``` /bin /dev /etc /lib /sbin ```

There are several approaches to finding files. What commands do this? There are 4 of them 4-222,223,224

find, locate, whereis, which