Basic unix commands Flashcards

Question

How do I tar a directory of files and folders without including the directory itself?

Answer 1

``` $ mkdir my_directory $ touch my_directory/file1 $ touch my_directory/file2 $ touch my_directory/.hiddenfile1 $ touch my_directory/.hiddenfile2 $ cd my_directory/ && tar -zcvf ../my_dir.tgz * && cd .. ./ ./file1 ./file2 ./.hiddenfile1 ./.hiddenfile2 $ tar ztf my_dir.tgz ./ ./file1 ./file2 ./.hiddenfile1 ./.hiddenfile2 ```

Answer 2

tar in itself just bundles files together, while zip applies compression as well. Usually you use gzip along with tar to compress the resulting tarball, thus achieving similar results as with zip

Answer 3

find -iname \*.tar -exec tar -xvf {} \ if can't think of exec or xargs, rate 1

Answer 4

tar xvfj file.tar tar xvfj file.tar -C path of file in directoy didn't understand the question , rate 1 options specified? no? then rate 2 don't remember the solution, rate 3

Answer 5

tar tvf file.tar | grep "text to find" tar tvf file.tar | grep "filename.file extension" don't remember the command to use, rate 1 didn't understand the question , rate 1 --wilcards can't be used?

Answer 6

tar tvf file.tar filename don't remember the argument to use at the end, rate 1 didn't understand the question , rate 1

Answer 7

tar tvf file.tar don't remember the argument to use at the end, rate 1 didn't understand the question , rate 1

Answer 8

tar cvf archive_name.tar dirname/ don't remember the options to use , rate 1 didn't understand the question , rate 1

Answer 9

``` $ ls abc def $ tar cvf compressed.tar abc def abc def $ ls abc compressed.tar def ``` if dont know that passing specified filenames is an option to tar only them, rate 1

Answer 10

tar tvf archive_name.tar didn't understand the question , rate 1 don't know listing imples option t, rate 1

Answer 11

tar tvfz archive_name.tar.gz tar tvfj archive_name.tar.bz2 didn't understand the question , rate 1 don't know listing imples option t, rate 1 don't know what compressed archive imples option t, rate 1

Answer 12

do u know this very well?

Answer 13

tar -cf - /directory/to/archive/ | wc -c

Answer 14

find -name techmint.txt /path/to/current/working/dir shouldn't be your answer The right answer is find . -name techmint.txt ``` -name option if not specified, rate 1 if doesnt strike that . = current working dir, rate 1 command arguments(not options) in same order or not? no -rate 2 ```

Answer 15

find /home -name techmint.txt if not specified the full file name with extensions, rate 3

Answer 16

find /home -iname techmint.txt if not specified the full file name with extensions, rate 3 if not specified the i letter before name , rate 1

Answer 17

find / -name Techmint The question implies that techmint is the name for multiple directories, if dont understand this -rate 2 if any quotations are added, rate 4 coz its plain-no quotations

Answer 18

find . -type f -name techmint.php if missed the type -f option-it could bring in directories with such name too(possible)- rate 2 If don't watch out that the question only asked for files and not the directories- rate 1

Answer 19

find /path/to/dir -type f -name "*.php" If don't understand that its a wildcard or regex -rate 2 if don't put it in "", rate 2 if don't put along with the -name option, rate 1

Answer 20

find . -type f -perm 0777 -print if don't know that / means check all dirs in current dir, rate 1 if are specific that you want to print to std out like screen, rate 5

Answer 21

find . -type f ! -perm 0777 -print if don't know that ! means a negation before an option, rate 1

Answer 22

find . -type f -perm 2644 if the first bit is set to 2 , sgid bit is set-dont know this rate 1

Answer 23

find . -type f -perm 1551 if the first bit is set to 1 , sticky bit is set-dont know this rate 1

Answer 24

find . -type f -perm /u=s if don't remember that -perm option is used, rate 1 if don't remember the argument to -perm userid set bit which is /u=s(set suid), rate 1

Answer 25

find . -type f -perm /g=s if don't remember that -perm option is used, rate 1 if don't remember the argument to -perm userid set bit which is /g=s(set sgid), rate 1

Answer 26

find . -perm /u=r if don't remember that -perm option is used, rate 1 if don't remember the argument to -perm userid set bit which is /u(user)=r(read), rate 1

Answer 27

find . -perm /u=x if don't remember that -perm option is used, rate 1 if don't remember the argument to -perm userid set bit which is /a(any user or all )=x(execute), rate 1, use /u(user)=x rate 3

Answer 28

find . -perm 0777 -exec chmod 0644 {} /; If don't remember that -perm option is used, rate 1 if don't remember that -exec option is used, rate 1 if don't remember that {} '; syntax is at the end of -exec option, rate 1 If don't remember that -chmod option is used to set permissions, rate 1

Answer 29

find . -type d-perm 0777 -exec chmod 0644 {} /; if don't note that the permissions are to be set for directories, rate 1 If don't remember that -chmod option is used to set permissions, rate 1 If don't remember that -perm option is used, rate 1 if don't remember that -exec option is used, rate 1 if don't remember that {} '; syntax is at the end of -exec option, rate 1

Answer 30

find . -name techmint.txt -exec rm -rf {} /; If don't remember that -rm option for deleting or removing, rate 1 If don't remember that -perm option is used, rate 1 if don't remember that -exec option is used, rate 1 if don't remember that {} '; syntax is at the end of -exec option, rate 1

Answer 31

find . -name "*.txt" -exec rm-rf {} /; if don't remember multiple files with a pattern has to be in " ", rate 1

Answer 32

find . -type f -empty if don't remember , -empty is an option , rate 1

Answer 33

find . -type d -empty if don't remember , -empty is an option , rate 1 if don't notice the question is on directories , and use -type d , rate 1

Answer 34

find . -type f -name " .*" if don't remember that . is the pattern of the hidden file start-rate 1

Answer 35

find / -type f -user root -name techmint,txt if don't remember that the option is -user ,rate 1 if the options are in wrong order, rate 3 if dont rememeber / corresponds to root dir, rate 1

Answer 36

find /home -user Techmint -type f if added any extra options like -name , rate 1 if the options are in wrong order, rate 3

Answer 37

find /home -group developer -type f If don't remember that the option is -group ,rate 1 if added any extra options like -name , rate 1 if the options are in wrong order, rate 3

Answer 38

find /home -type f -iname "*.txt" -user Techmint if don't remember that the option is -user ,rate 1 if the options are in wrong order, rate 3 if dont rememeber / corresponds to root dir, rate 1

Answer 39

find . -type f -mtime 50 if don't remember that the option is -mtime ,rate 1 if have any + or - sign , rate 3,since asked just precise 50 days

Answer 40

find . -type f -atime 50 if don't remember that the option is -atime ,rate 1 if have any + or - sign , rate 3 ,since asked just precise 50 days

Answer 41

find . -type f -mtime +50 -mtime -100 If don't remember that the option is -mtime ,rate 1 If don't remember that the option is -mtime should be used two times to specify range ,rate 1 f don't remember that the option is -mtime arguments have +, - signs ,rate 1

Answer 42

find . -type f -cmin 60 if confused with cmin and mmin, rate 3 if don't remember the cmin option, rate 1 if don't remember the arguments are in minutes count, rate 1

Answer 43

find . -type f -mmin 60 if confused with cmin and mmin, rate 3 if don't remember the cmin option, rate 1 if don't remember the arguments are in minutes count, rate 1

Answer 44

find . -type f -amin 60 if confused with cmin and mmin, rate 3 if don't remember the cmin option, rate 1 if don't remember the arguments are in minutes count, rate 1

Answer 45

find / -type f -size 50M if don't remember the -size option, rate 1 if don't remember the option's argument needs to specify the unit of size, rate 1

Answer 46

find / -type f -size +50M -size +100M If don't remember that the option is -size ,rate 1 If don't remember that the option is -size should be used two times to specify range ,rate 1 f don't remember that the option is -size arguments have +, - signs ,rate 1 if don't remember the option's argument needs to specify the unit of size, rate 1

Answer 47

find / -type f -size 100M -exec rm -rf {} /; if don't remember the -size and -exec for deleting -rm, rate 1

Answer 48

find / -type f -name "*.mp3" -size +10M -exec rm -rf {} /;

Answer 49

``` Type Regular file Directory file Block file Character file Pipe file Symbolic link file Socket file. ```

Answer 50

find / -perm /o=t if dont know o means others and t is for sticky, rate 1

Answer 51

find / -perm /u=r if don't know u means owner and r is for read pnly , rate 1

Answer 52

find / -perm /a=x if don't know a means owner, user and all others and x is for execution , rate 1

Answer 53

find / -newer newertxt need to know that -newer is an option, rate 1 if no

Answer 54

find / -type -f -size +10c if don't now that c is used for bytes notation of size in units, rate 1

Answer 55

find /opt -type -f -size 10k if don't now that k is used for kilo bytes notation of size in units, rate 1

Answer 56

find /opt -type -f -size 0k if don't now that k is used for kilo bytes notation of size in units for empty files too , rate 1

Answer 57

find /opt -type -f -size +1G if don't now that G is used for giga bytes notation of size in units, rate 1

Answer 58

find /opt -size 100M -group sales -perm g+s -name pass.txt

Answer 59

find / -size +100M -size -1G if don't know to put appropriate units near the -size's argument, rate 2

Answer 60

find /var -iname passwd.txt -exec ls -l {} ; if dont remeber long listing option is for ls , rate 1

Answer 61

find /mnt -type f -name test.txt -user Surendra -exec chown Narendra {} \; if don't remember that exec needs to be used, rate 1 if don't remember that chown needs to used with exec to do modifications on the found files, rate 2 if added extra options with chown, rate 3

Answer 62

find /mnt -type f -inode 23 if don't remember the inode number , then rate 2

Answer 63

find /abc -type f -name test.sh -exec grep "for" {} \;

Answer 64

find /var/ftp/pub -type f -name xyz.txt -user Surendra -exec chmod 775 { } \; make sure you have included all the filter options, rate 4 if missed

Answer 65

find /xyz -type f -name temp.txt -exec tar -cvfz backup.tar.gz {} /; any small obvious mistake , rate 1

Answer 66

find /xyz -type f -name temp.txt -exec cp {} {}.bkf /; If doesn't strike to use cp command, rate 1 if don't remember that cp follows w=by the current path of the file represented by {} in -exec command , rate 1 If don't remember the cp syntax, rate 1

Answer 67

find /con -type f -perm /a=x -exec -md5sum {} \; if don''t remember that md5sum is the command for the checksum, rate 1

Answer 68

find /com -type f -name abc.txt -user surendra -exec mv {] /opt/ \; If doesn't strike to use mv command, rate 1 if don't remember that mv follows by {}. rate 1 the current path of the file represented by {} in -exec command , rate 1 If don't remember the mv syntax, rate 1

Answer 69

find /com -type f -name abc.txt -user surendra -exec chown Narendra \; -exec chmod 775 \; If you don't remember that We can use this multiple -exec option more than two times, rate 2

Answer 70

find /opt /var -name abc.txt If you don't remember that two locations can be specified side by side, rate 2

Answer 71

find /opt /var -path /proc -prune -name abc.txt if don't remember this - The -path variable to define the path of a location. And -prune combined with -path will say not to descend in to the mention path /proc- rate 1

Answer 72

find /opt /var -name abc.txt -o -name hash.c if don't know that the -o should be followed by the specific previous option , rate 3 if don't know h=that -o option should be used to find for something together, rate 1

Answer 73

find . -type d -name opt -o -type d-name var if don't understand the question, rate 1 if doesn't strike that its type d option, rate 1

Answer 74

find . -maxdepth 1 -type f -newer first_file if don't remember the maxdepth option, rate 1

Answer 75

find . -type l -print0 | xargs -o ls -ld | awk '{print $10}' 10th field has the actual link pointing, remember if forgot, rate 3 if forgot about the awk syntax, rate 2 if forgot about symbolic links , rate 1

Answer 76

know this or not

Answer 77

executable files

Answer 78

config files

Answer 79

only temporary files, they clear during boot time

Answer 80

installing software not bundled with os

Answer 81

log files created by programs and applications

Answer 82

mount point for files on cdrom

Answer 83

mount point for cdrom and dvd

Answer 84

web files, ftp server files /srv/ftp

Answer 85

executable files

Answer 86

configuration files

Answer 87

ls -F @ link / dir * binary executables

Answer 88

./binaryfilename

Answer 89

ls -r yes with ls -R which is a recursive listing not reverse listing

Answer 90

tree -d | tree - c to colorize output

Answer 91

ls --color

Answer 92

vi filename

Answer 93

3 | command, insert, line

Answer 94

i - to insert right at after the cursor

Answer 95

h left j down k up l right

Answer 96

type : followed by the command

Answer 97

/pattern ( n for next, N for previous match)

Answer 98

? n for next, N for previous match

Answer 99

ps -u root

Answer 100

ps -e --forest | pstree

Answer 101

they specify storage location and has a name and a value, they affect the way programs behave

Answer 102

TZ,HOME,PATH

Answer 103

echo $ENVIRONMENT VARIABLE NAME($HOME)

Answer 104

export VAR='value'

Answer 105

export EDITOR="vi" | export TZ="US/Pacific"

Answer 106

vi .bash_profile ``` insert mode, go to the end export TZ="US?Pacific" :wq! exit login to shell printenv TZ or echo $TZ ```

Answer 107

pipe the output to less command

Answer 108

man commandname will display the man pages with a section on environment variables

Answer 109

fg %jobid ;fg %3

Answer 110

bg %jobid; bg (will background the latest process evoked)

Answer 111

``` kill %jobid; kill %3 kill pid; kill 103458 kill -TERM pid; kill -TERM 123 kill 15 123 kill -9 123 (9 kill signal) ```

Answer 112

cron services

Answer 113

cron job starts when the system boots, it performs routine maintenance and it automates a process

Answer 114

``` min hr dom month dow /path/to/the/executable/file min(0-59) hr(0-23) (dom= day of the month) (1-31) (dow=day of the week)(0-6) ```

Answer 115

min hr dom month dow | 0 19 * * 1 /opt/sales/bin/weekly-report

Answer 116

``` 0,30 * * * * /opt/sales/bin/weekly-report */2 * * * * /opt/sales/bin/weekly-report ```

Answer 117

0-5 * * * * /opt/sales/bin/weekly-report

Answer 118

0 0 1 1 * /opt/sales/bin/weekly-report

Answer 119

0 0 * * 0 path/to/the/executable/file

Answer 120

0 0 1 * * path/to/the/executable/file

Answer 121

0 0 * * * path/to/the/executable/file

Answer 122

0 * * * * path/to/the/executable/file

Answer 123

chrontab command

Answer 124

crontab file

Answer 125

crontab -l

Answer 126

crontab -e (should open ur favrt editor: set an environment variable)

Answer 127

crontab -r

Answer 128

1) open a vi editor with the file name => vi my-cron 2) in insert mode type 07 **1 /opt/sales/bin/weekly-report 3) :wq! 4) install the file with crontab command => crontab my-cron 5) echo $ EDITOR 6) export EDITOR =vi 7) crontab -e to do any edits

Answer 129

su with no arguments

Answer 130

su -C command; su -C ls -l

Answer 131

su oracle ( with out - before the user name )

Answer 132

su - oracle (with the - and space followed by a username)

Answer 133

sudo -u sqoop command

Answer 134

sudo su - sqoop command

Answer 135

sudo -u sqoop -s

Answer 136

sudo visudo

Answer 137

scp source destination scp z.txt linuxserver(hostname):~ (~ shortcu for hoe dir)

Answer 138

sftp linuxserver pwd ls lpwd # local path to directory lls # local list files put z.txt ls rm z.txt quit

Answer 139

scp z.txt adminuser@linuxserver:/home/adminstration or sftp adminuser@linuxserver pwd ls lpwd # local path to directory lls # local list files put z.txt ls rm z.txt quit

Answer 140

diff file1 file2

Answer 141

file1lineno change - c file2lineno

Answer 142

sdiff file1 file2 or vimdiff file1 file2 (to view ffiles in two diffent windows) | symbol for differing lines > lines exist only in 2nd file < lines exist only in 1rst file

Answer 143

rm -r -dir

Answer 144

cp file1 file2 /home

Answer 145

cp -r file /newdir

Answer 146

mv source destin

Answer 147

sort -k 10 # 10 is field no

Answer 148

du ``` then gzip then check du then tar gzip and view contents of the tar gzip file ```

Answer 149

egrep is to search for multiple patterns with pattern having a pipe character eg: egrep "PATTERN1|PATTERN2" FILE grep is for searching patterns as a string, any special characters are needed to be escaped eg: grep "PATTERN1\|PATTERN2" FILE

Answer 150

grep, egrep, sed, awk

Answer 151

$ grep -E -o "\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,6}\b" file.txt

Answer 152

grep -E -o "([0-9]{1,3}[\.]){3}[0-9]{1,3}" file.txt

Answer 153

53, 123 and 111/2049

Answer 154

All configuration files are located in /etc directory and the name of the DNS configuration file is named.conf. /etc/named.conf

Answer 155

No because it will create IP conflict

Answer 156

Check for /etc/hosts or DNS to see if it has hostname to IP entry

Answer 157

Absolute path starts from / where relative path is your current directory

Answer 158

1) The adduser command automatically creates a home directory and sets the default group, shell, etc. To create a new standard user with the adduser command the syntax is as follows: sudo adduser bob 2) Anytime you add a user, that user is added to the passwd file,You can edit the file directly or use the commands we will go over shortly - useradd roman 3) useradd bob passwd

Answer 159

chown and chgrp

Answer 160

ext4, NTFS FAT

Answer 161

A user of an operating system can expect to find executable files in binary.

Answer 162

passwd username

Answer 163

Windows, Linux and MAC

Answer 164

Redhat, CentOS, Ubuntu and SUSE

Answer 165

/var/named/zonefiles

Answer 166

uname –a

Answer 167

So the communication of each application goes through a dedicated port

Answer 168

cat filename | awk ‘{print $1}’

Answer 169

kill will create a sigterm signal. kill -9 willforcefull kill the process

Answer 170

tar (compress) the entire /etc directory and sftp or scp

Answer 171

First 3 bits should have x

Answer 172

1) provides a method of communication between kernel space and user space. 2) the process reporting utility ps uses the proc file system to obtain its data, 3) special filesystem in Unix-like operating systems that presents information about processes and other system information in a hierarchical file-like structure

Answer 173

cd, pwd and ls

Answer 174

1) it provides a barrier to control network traffic both into and out of an organization’s Internet-connected network, or perhaps between different segments of an internal network. 2) companies can configure multiple firewalls inside their corporate network to essentially divide the network into multiple segments. That helps contain the damage should some form of worm or other malware be unleashed in any given segment.

Answer 175

Hardware, OS and Applications

Answer 176

virtual memory: memory in db server or any virtual machine memory cache: active memeory sits between cpu and memory physical memory: memory

Answer 177

/usr/bin or /bin

Answer 178

o grep o mail this one o touch o cd

Answer 179

sudo nano /etc/hosts | sudo nano /etc/hostname

Answer 180

“tail –f logfilename”

Answer 181

cat filename | sort –r

Answer 182

Solaris, HP-UX etc

Answer 183

bytes, kilobytes, megabytes,gigabytes,terabytes

Answer 184

cat filename | awk ‘{print $5}’ | cut –c1-3

Answer 185

To resolve hostnames with IP address

Answer 186

df -h df -x tmpfs to exclude certain filesytem types df -t ext4 list only specific file system types df -T To show the file system type pass the -T option

Answer 187

To combine multiple commands

Answer 188

For configuration files

Answer 189

rm filename and rmdir dirname

Answer 190

cat, more, less, vi

Answer 191

head -5 filename

Answer 192

echo > filename and vi filename

Answer 193

top command shows swap space, swap space is the amount of memory reserved for a process which is equivalent to amount of memory assigned to the process by the kernel., when the physical memory passes its threshold then the swap space is activated,the inactive

Answer 194

1) An inode is simply an internal data structure that Linux uses to store information about a filesystem object 2) ls -id /path/to/dir ``` i = inode d= directory ```

Answer 195

1) /etc/sysctl.conf you can configure various Linux networking and system settings

Answer 196

grep word filename

Answer 197

Check your system time Check your crontab entry Check /var/log/messages

Answer 198

Remove r from the last 3 bits of file permission

Answer 199

1) uniq authors.txt, uniq command is of showing a count of occurrences, showing only repeated lines and ignoring characters and specific fields. uniq -c authors.txt To output the number of occurrences of a line use the -c uniq -d authors.txt This will output only lines that occur more than once and write the result to standard output In summary the purpose of uniq is to parse data a 2) sed is a stream editor. A stream editor is used to perform basic text transformations on an input stream (a file or input from a pipeline). ``` for eg: the input file is Tom Westley Essex Ravi Bopara Essex Marcus Trescothick Somerset Joe Root Yorkshire Jonny Bairstow Yorkshire ``` uniq -f 2 -c cricketers.txt | sed 's/^\s*//' | cut -d ' ' -f 1,4 2 Essex 1 Somerset 2 Yorkshire To ignore fields in a comparison pass the -f option to uniq. This will run the comparison on the specified field and output the result to standard output. ^/s* zero or more occurences of space is replaced by1 single space " " to make a solid delimiter for cut command The cut command in UNIX is a command line utility for cutting sections from each line of files and writing the result to standard output. In summary, the sed and uniq command are for data transformation.

Answer 200

ls –ltr explanation: ls -ltr : - t option will sort the entries by modification date (with newest first) - r will reverse the sorting order. As -t will sort by modification time with newest first, -r will cause the reverse i.e. oldest entries will be shown first now.

Answer 201

Tar is a file archiving technique and it combines mulitple files to a single archive file gzip is to compression technique to compress a file which has large file gunzip is to decompress the compressed file that was compressed using the gzip technique

Answer 202

diff file1 and file2

Answer 203

grep -v "^#" filename

Answer 204

.bash_profile is executed when newly logged in to the shell session. .basharc is executed when already logged in but opened a new trminal

Answer 205

$ prompt is for users and # prompt is for root

Answer 206

/etc/named.conf

Answer 207

ext3,ext4, xfs,fat,ntfs

Answer 208

fedora ubuntu redhat suse

Answer 209

file filename

Answer 210

for eg to check if DNS package is installed rpm -qa | grep bind

Answer 211

which passwd

Answer 212

ls /usr/bin

Answer 213

ifconfig -a

Answer 214

wc -l filename

Answer 215

/etc/ntpd.conf

Answer 216

to show last logged in users

Answer 217

1) Run the df command to find out info about the total space and available space on a file system including partitions 2) Locate the filesystem that has unusually high usage 3) When the disk is full, du on the /var/logs and tar the files where the directory is large on du 4) compress the tar files either usng gzip or bzip technique. 5) Delete unwanted files using rm , and unwanted directories using rmdir 6) Move files to other systems or external hard disk rsync --remove-source-files -azv /ftp/tmp/*.log /mnt/usbdisk/ rsync --remove-source-files -azv /ftp/tmp/*.log server2:/path/to/the destination/directory 7) find largest dir or files eating disk space on unix system du -a /ftp/tmp | sort -n -r| head -n 10 8) locate those largest files and truncate the largest files on unix/linux truncate -s 0 /ftpuser/ftp.log 9)find and remove large files that are open but have been deleted on unix lsof -np | grep 'deleted' 10) Check if you are running out of inodes, coz most likely when 1000's of small files are created on a dir, the ifilesystem runs out of inodes. To check this out we can use du -i /dirname/filename.ext if 100 % of inodes are used, we need to find the unwanted files and delete them after transfering them to different server or mount point using rsync command 11) du -hs points to the biggest directory and points to what needs cleaning up

Answer 218

1) Run the df command to find out info about the total space and available space on a file system including partitions 2) Locate the filesystem that has unusually high usage 3) When the disk is full, du on the /var/logs and tar the files where the directory is large on du 4) compress the tar files either usng gzip or bzip technique. 5) Delete unwanted files using rm , and unwanted directories using rmdir 6) Move files to other systems or external hard disk rsync --remove-source-files -azv /ftp/tmp/*.log /mnt/usbdisk/ rsync --remove-source-files -azv /ftp/tmp/*.log server2:/path/to/the destination/directory 7) find largest dir or files eating disk space on unix system du -a /ftp/tmp | sort -n -r| head -n 10 8) locate those largest files and truncate the largest files on unix/linux truncate -s 0 /ftpuser/ftp.log 9)find and remove large files that are open but have been deleted on unix lsof -np | grep 'deleted' 10) Check if you are running out of inodes, coz most likely when 1000's of small files are created on a dir, the ifilesystem runs out of inodes. To check this out we can use du -i /dirname/filename.ext if 100 % of inodes are used, we need to find the unwanted files and delete them after transfering them to different server or mount point using rsync command 11) du -hs points to the biggest directory and points to what needs cleaning up

Answer 219

1) Run the df command to find out info about the total space and available space on a file system including partitions 2) Locate the filesystem that has unusually high usage 3) When the disk is full, du on the /var/logs and tar the files where the directory is large on du 4) compress the tar files either usng gzip or bzip technique. 5) Delete unwanted files using rm , and unwanted directories using rmdir 6) Move files to other systems or external hard disk rsync --remove-source-files -azv /ftp/tmp/*.log /mnt/usbdisk/ rsync --remove-source-files -azv /ftp/tmp/*.log server2:/path/to/the destination/directory 7) find largest dir or files eating disk space on unix system du -a /ftp/tmp | sort -n -r| head -n 10 8) locate those largest files and truncate the largest files on unix/linux truncate -s 0 /ftpuser/ftp.log 9)find and remove large files that are open but have been deleted on unix lsof -np | grep 'deleted' 10) Check if you are running out of inodes, coz most likely when 1000's of small files are created on a dir, the ifilesystem runs out of inodes. To check this out we can use du -i /dirname/filename.ext if 100 % of inodes are used, we need to find the unwanted files and delete them after transfering them to different server or mount point using rsync command 11) du -hs points to the biggest directory and points to what needs cleaning up

Answer 220

1) It happens when the query execution time exceeds the normal time 2) There will already by some shell scripts created by primary admin or system admin. 3) So, whenever the application is down, run the scripts 4) if the scripts don't work, accelerate the issue either to the system admin or the server admin 5) Sometimes the script requires to pass arguments to the scripts, we can either go and edit certain part of the script using the vi editor

Answer 221

./shellscript.sh argument1 argument2 argument3 2 "Newyork"

Answer 222

$# wil output the number of arguments specified to the script

Answer 223

Shebang is a pound symbol followed by an exclamation #! This syntx is used in scripts to indicate an interpreter for the execution under linux/unix os for eg #!/bn/bash would mean the shell script should be executed with the bash interpreter #! /usr/bin/prl meaning it should execute using the interpreter specified on a first line

Answer 224

1) Both are used to execute the script 2) Howewer sh scriptname will make it execute under sh 3) ./ could execute under bash/perl/sh/etc whatever interpreter specified in its shebang line

Answer 225

Each process is allocated some java heap size for eg 3gig has been alloted to one process However a user has started downloading a 600 MB excel file and now the process is taking 4GB RAM , then that particular process throws out of memory exception, since it's demanding more than what's allocated to it. The ways to troubleshoot this issue is: 1) If we have a shell script to auto-restart the process, we will go ahead and run it 2) If the process hangs, we will kill it or teminate it

Answer 226

We have couple of options 1) Reduce amount ofmeory asked by the process 2) Disallow process to overcomit memory 3) Simply add more memory to the server configuration > A useful memorymonitoring tool is the top command > If your system memory gets used up to the extent that it can threathen the system stability, the out of memory killer will choose which process to terminate or eliminate and linux keeps a score for each running process for this purpose and it's called oom score and this score is stored in the file /proc//oom_score ps aux |grep processname will give the processid cat /proc/pid/oom_score can give the score, higher the number more likely its can be eliminated. >Now to change the overcommit mode if the system is at risk of running out of memory, sudo sysctl -w um.overcomit_memory=2 2 meaning if system doesnt have meomry it will not overcommit other options include 1 to always allow 0 estimate if we have enough RAM

Answer 227

sudo netstat -tunlp | grep 8080 t = tcp u =udp n= numerical display of addresses ,ip and ports l=list only listening ports p=show processid and name of the program to which the socket belongs

Answer 228

sudo lsof -i :80

Answer 229

ps -p 2212 -o -comm= or ls -l /proc//exc

Answer 230

whatis pwdx

Answer 231

both are used to connect remotely to the other servers remotely However, ssh is encrypted version of telnet - telnet sends data in plain text, if the usecase is for fast protocol,telnet is the choice if the usecase if for security, ssh is the choice-its a slow protocol due to encryption.

Answer 232

1) During establishing connections to other computers firewall issues may be encountered 2) So we need to make sure that port is open in the firewall to listen 3) So wen use telent command to test ports opened or closed on a remote server as follows: telnet domainnameorIP port eg. telnet adminuser@google.com 80 Due to security issues of transferring data in plain text most use ssh 4) We can use ping to know if the ip or port are active, but most likely this will be disabled 5) After port issue is established, another issue that can be causing this is ip restriction ifconfig is to query network interface parameters, using this we can figure out if the ip address is resolved with the particular hostname

Answer 233

Will continuously monitor log files for errors, this way I can keep tabs on the live feed of data coming into the log file : var/log/messages tail -f /var/log/messages AND use Cntrl C to exit

Answer 234

/var/log/messages

Answer 235

I will not use cat command as it can potentially hang the system I will use the tail -f /varlog/messages

Answer 236

vi filename | 0 0 * * * /bin/find -mtime +7 -exec rm -rf {} ;/

Answer 237

tar -cvf users.tar /etc/passwd | awk '{print $1}' >file.ext tar -cvf users.tar /etc/passwd | cut d ':' -f 1 >file.ext sftp file.ext server2:/destination/dir

Answer 238

touch or vi used to create a file, | awk and cut can be used to pront out the first column

Answer 239

cut -d ' ' -f 2

Answer 240

wall -n "server is going down in 15 mins"

Answer 241

useradd -s /sbin/nologin username then su username to check

Answer 242

shutdown -r 15

Answer 243

shutdown -r now

Answer 244

shutdown -r 23:00

Answer 245

this can be troubleshooted by checking disk space pertaining to a particulr user or by particular directory and sub directories pwd /var du -Sh | sort -n | less S is for searching disk space for directories

Answer 246

This question is pointing towards special permissions that are called sticky bit chmod 1777 hist/

Answer 247

cat filename | head -n 10 | tail -n 1

Answer 248

There are two parts in this question: Vmware and physical server 1) If I am using VMware and ther is a complete copy of that disk, VM has a tool in it that captures the ystems state off a particular system or depending on which date it's capturing from , you can completely redo the system from that particular date. we can restore it from the system state if VMware has saved it to some kind of capture tool that captures the whole system and deploys that image for that system 2) If it's the physical server , then only the data gets backedup , also some config files can be restored not all. We can restore the entire OS just from the back up and use the data from the back up taped device Config files are restored in /etc files So to summarize , we create a new system, get all the data from the back up and throw them on your new system.

Answer 249

yum update

Answer 250

yum remove packagename

Answer 251

service servicename stop

Answer 252

Unix was primarily developed with multi tasking and multi users in ind, unix cannot be installed on any hardware. Where as linux can be installed in almost many hardwares and supports may flavors of file system, whereas unix supports only fewer filesystems.

Answer 253

Linux is an operating system sits between hardware and users

Answer 254

free not free not user friendly userfreindly very secure not so secure very open to public can modify ur own changes Not an open surce os, cannot open the code or reveal to anyone Best for multi tasking multi tasking requires high cpu and mem

Answer 255

ifconfig command is deprecated, | ip addr

Answer 256

A filesystem is something similar to your closet at your hoe. Think of each shelf with specific kind of storage. One folder has only programs or applications, another folder have only attaced devices, so it will be much easier for the operating system to access the files, ``` There are different types of filesystems: 1)ext3 ext4 FAT NTFS XFS ```

Answer 257

touch command eg: touch mart lisa tex

Answer 258

touch command eg: touch mart lisa tex

Answer 259

mkdir dir1 dir2

Answer 260

if any eboard of mouse is attaches, then that file starts with c

Answer 261

named pipe file starts with p

Answer 262

block device starts with b

Answer 263

find and locate

Answer 264

touch abcd{1...9}-xyz this will create 9 files wildcards are to substitute for charecters

Answer 265

^ and $ respectively

Answer 266

it is related to inode. Inode is a pointer of a file on the hard disk Eevrytime we create a file, computer assisgns a number to the file and hard disk will associate that number to it and that number is called inode Soft link is a link if when created will be removed if the filname of that link is removed or renamed once created it looks for the inode through that file, so that creates a soft link, if removed the source file it removes the destination link whereas for hard link, deleting or renaming the source file will not change the hard link, as if you have copied it

Answer 267

to creata shortcut of the actual file, to have easy access instaed of doing a lot directory chnages or specifying the long path to the file

Answer 268

cd /tmp ln -s /home/hulk to check that the link got created ls -ltr command , at the botto of the output the file is seen

Answer 269

This happens when the hard link is created on the different partition. . For the hard link to work, it needs to be on the same partition.

Answer 270

Since unix is a multi user system. typically for protecting our environment where files could be viewed by other users, or unnecessarily modified or deleted by other users

Answer 271

ls -l command, the first 3 bits are for the user the second three bits are for the group the last three bits are for the other users of the system

Answer 272

chmod g-w filename

Answer 273

chmod a-r filename

Answer 274

chmod u+rw filename

Answer 275

It certainly doesnot mean it is a script, what it means is we cannot cd into that directory

Answer 276

chown and chgroup that an be changed from the root account

Answer 277

chown root filename

Answer 278

chgroup root filename

Answer 279

hitting a tab key after the command completes the command

Answer 280

type ch and press tab twice

Answer 281

up arrow key

Answer 282

``` top free df dmesg netstat iostat cat proc/cpuinfo cat proc/meminfo ```

Answer 283

df reports filesystem usage of disk

Answer 284

df command

Answer 285

to free up the disk space an, and the comand to help in this pursuit is du which will output the disk usage of the files and the directories

Answer 286

It throws bunch of messages and bunch of information at you , and that command is dmesg If there are any issues with the memory it will report right here , if there is a memory leak, cpu that crashed or any mother board issue, anything related to system hardware will be related to that

Answer 287

netstat -rnv

Answer 288

It gives you information about the virtual memory and the swap space which is a virtual memory utilization

Answer 289

cat /proc/cpuinfo

Answer 290

cat /proc/boot.log |more

Answer 291

/var/directory

Answer 292

cat /var/boot.log |more

Answer 293

cat /var/cron

Answer 294

/var/maillog

Answer 295

/var/maillogs

Answer 296

tail -f /var/secure

Answer 297

look into the /var

Answer 298

/var/messages

Answer 299

cat /var/messages | wc -l

Answer 300

go to sysctl.conf net.ipv4.icmp.ignore_echo_ignore_all = 1 that parameter 1 will disable the ping, the parameter 0 will enable it

Answer 301

username uid groupid shellname uid gid home drectory

Answer 302

netstat -tunlp | grep 22

Answer 303

average number of processes that are in runnable state or uninterrupted state

Answer 304

cat -n filename

Answer 305

go to /etc/sysconfig/network-scripts/ifcfg-empos3

Answer 306

rpm -qa | grep packagename rpm -qa | grep ntp

Answer 307

rpm -qa | grep bind

Answer 308

rpm command is a powerful package manager

Answer 309

wc -l filename

Answer 310

no don't do cat on large files

Answer 311

du -Sh |sort -nr | head -n 10

Answer 312

find / -type d -name conf

Answer 313

sos repor is a package of all the sysyem congifuration informations, all the processes and all the resources information packaged and send t redhat for support

Answer 314

cat file1 file2 file3 > file4

Answer 315

split -l 300 filename childfile

Answer 316

echo uk >>filename

Answer 317

know this?

Answer 318

nohup processname &

Answer 319

nice is the command to set priority of a process, the nice value ranges from -19 to 20, lower the number more priority the task gets. nice -n process command

Answer 320

systemctl restart ntpd d means daemon

Answer 321

its a daemon and is a network time protocol that runs all the time and syncs your time with other clocks

Answer 322

systemctl status ntpd

Answer 323

systemctl stop ntpd

Answer 324

systemctl enable ntpd this will start the ntpd daemon whenevr the system strts

Answer 325

top command that shows 99% of usage of mem and cp

Answer 326

cd /usr/bin | ls -l

Answer 327

only then the uniq command works | sort | uniq

Answer 328

1) add new disk 2) initialize the disk 3) Patition the disk 4) mount it to the different mount points

Answer 329

when u run out of the disk space or if you have multiple applications may be one partition is required for one application and other partiton is required for another application, that's why we ask new disk

Answer 330

when u run out of the disk space or if you have multiple applications may be one partition is required for one application and other partition is required for another application, that's why we ask new disk

Answer 331

zip -r filename /path/to/dir/to/zip

Answer 332

unzip filename -d dire/where/to/unzip/into

Answer 333

sar -p ALl

Answer 334

sar -p 4 (here 4 is the core number)

Answer 335

sar commadn with it's different options

Answer 336

sar -u -f /varlog/sa/sa15

Answer 337

iostat -p partition-device-name

Answer 338

last reboot

Answer 339

last shutdown

Answer 340

last -t 201801030300

Answer 341

last username

Answer 342

compress filename

Answer 343

compress -rv filename

Answer 344

du -a filename

Answer 345

add more disk, create a new partition and link the new partition to an existing file-system

Answer 346

TCP and UDP are protocols used for sending bits of data — known as packets — over the Internet. The main difference between TCP and UDP is connection; TCP is connection oriented and UDP is connectionless. TCP is all about reliability—packets sent with TCP are tracked so no data is lost or corrupted in transit UDP is used when speed is desirable and error correction isn’t necessary. For example, UDP is frequently used for live broadcasts and online games

Answer 347

sed -n '5,10p' file.txt

Answer 348

sed '20,35d 'file.txt'

Answer 349

sed -n -e '5-7p' -e '10-13p' myfile.txt

Answer 350

sed 's/version/story/g' myfile.txt

Answer 351

sed 's/version/story/gi' myfile.txt

Answer 352

sed 's/ */ /g' myfile.txt

Answer 353

sed '30,40 s/version/story/g' myfile.txt

Answer 354

sed '/^##/|^$/|*#/d' myfile.txt

Answer 355

blank lines

Answer 356

sed 's/[zZ]ip/rar/g' file.txt

Answer 357

sed -n '/^ Jul 2/p' file.txt

Answer 358

sed G file.txt

Answer 359

sed 'G;G' file.txt

Answer 360

sed -i '.orig' 's/this/that/gi' myfile.txt

Answer 361

sed 's/^$.*$\,$.*$/$/2\,/1' fil.txt

Answer 362

sed '/services/ s/start/stop/gi' file.txt

Answer 363

sed 's/this/that/gi;s/him/her/gi' file.txt

Answer 364

To understand what a zombie process is and what causes zombie processes to appear, you’ll need to understand a bit about how processes work on Linux. When a process dies on Linux, it isn’t all removed from memory immediately — its process descriptor stays in memory (the process descriptor only takes a tiny amount of memory). The process’s status becomes EXIT_ZOMBIE and the process’s parent is notified that its child process has died with the SIGCHLD signal. The parent process is then supposed to execute the wait() system call to read the dead process’s exit status and other information. This allows the parent process to get information from the dead process. After wait() is called, the zombie process is completely removed from memory. This normally happens very quickly, so you won’t see zombie processes accumulating on your system. However, if a parent process isn’t programmed properly and never calls wait(), its zombie children will stick around in memory until they’re cleaned up. Utilities like GNOME System Monitor, the top command, and the ps command display zombie processes.

Answer 365

sed 's/patter/replcer/gi' filename

Answer 366

To create an empty file

Answer 367

fdisk –l

Answer 368

print all the processes and only print the first column of all running processes and sort them and remove duplicates

Answer 369

Check for user internet Check to see if user computer has DNS for hostname lookup Check to see if the server is up that is running that website Check to see if the server’s web service is running Check for DNS availability which is resolving that website

Answer 370

/etc, /bin, /tmp, /home

Answer 371

It will show the first line from the last 10 lines of a file

Answer 372

username passwword uid group name group id fullname of the user user home directory user terminall login

Answer 373

Hostname will give you system name and uname will give you OS information

Answer 374

top and uptime command

Answer 375

Day of the month

Answer 376

systemctl restart servicename

Answer 377

shutdown or init 0

Answer 378

shutdown or init 0

Answer 379

To transfer files from one computer to another

Answer 380

rpm –e packagename

Answer 381

/etc/shadow

Answer 382

which chmod

Answer 383

ping othercomputer

Answer 384

A LAN (Local Area Network) is a group of computers and the network devices connected together usually within the same building. By definition, the connections must be high-speed and relatively inexpensive (e.g. token ring or Ethernet). A "LAN Connection" is a high-speed connection to a LAN. See "What is a LAN (local area network)?" below. A MAN (Metropolitan Area Network) is a larger network that usually spans several buildings in the same city or town. A WAN (Wide Area Network) is, in comparison, not restricted to a geographical location, although it might be confined within the bounds of a state or a country. A WAN connects several LANs, and may be limited to an enterprise (a corporation or an organization) or accessible to the public. The technology is high-speed, and is relatively expensive. The Internet is an example of a worldwide public WAN.

Answer 385

ssh is secure where telnet is not

Answer 386

bc and quit

Answer 387

top, df –h, iostat, dmesg

Answer 388

Check the system physically Login through system console Ping the system Reboot or boot if possible

Answer 389

A Static IP address is a dedicated IP address that has been assigned to you. This is an IP address that is used by you every time you log in to network and need an IP address. DHCP or Dynamic is an IP address that will automatically be chosen for you from a pool of IP addresses that are assigned in the DHCP scope available on your network. Think Static as permanent and DHCP as temporary.

Answer 390

i = insert, a = insert in next space, o = insert in new line

Answer 391

crontab is for repetitive jobs where at is for one time job

Answer 392

To get system information

Answer 393

/var/log directory

Answer 394

alias aliasname=”command” | It is used to created short-cuts for long commands

Answer 395

Netstat is a common command line TCP/IP networking utility available in most versions of Windows, Linux, UNIX and other operating systems. Netstat provides information and statistics about protocols in use and current TCP/IP network connections. netstat (network statistics) is a command line tool for monitoring network connections both incoming and outgoing as well as viewing routing tables, interface statistics etc. netstat is available on all Unix-like Operating Systems and also available on Windows OS as well

Answer 396

to resolve dns to obtain dns or ip addreses mapping for any other specific dns record

Answer 397

Crtl C, D and Z, tab and up arrow

Answer 398

ps -ef |awk '{print $1}' |sort |uniq|wc -l or simply | ps -ef |wc -l

Answer 399

sh, bash, ksh, csh etc.

Answer 400

a) Shell b) Kernel<< c) Commands d) Script

Answer 401

a) Shell b) Commands c) Kernel<< d) Applications

Answer 402

Shift ZZ or :wq!

Answer 403

A daemon is just a term for a process that runs continuously and usually is not attached to a terminal

Answer 404

top, iostat, df –h, netstat etc.

Answer 405

yum install packagename

Answer 406

ifconfig for Linux and ipconfig for Windows

Answer 407

Define shell | e.g. #!/bin/bash

Answer 408

/etc/sysconfig/network-scripts/ifcfg-nic

Answer 409

To see who has logged in the system whether active or logged off

Answer 410

history and history #

Answer 411

The server or usually called as web server is an actual place where your website files are hosted. ... The domain name is a pointer to an IP address which hosts a server. Think of it as the difference between the street address "Example Street 42" (the domain name) and the house on that address (the server).

Answer 412

crontab –l

Answer 413

free and top

Answer 414

systemctl enable servicename

Answer 415

cat fileA >> fileB

Answer 416

To output to a screen

Answer 417

/etc/sudoers

Answer 418

The /boot file is most likely corrupted

Basic unix commands Flashcards

to crack the interviews