- Displays entries from databases configured in /etc/nsswitch.conf - Most commonly used to query passwd, hosts, group, and services

2015 Updates Flashcards by Matt Miller

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Displays entries from databases configured in /etc/nsswitch.conf
Most commonly used to query passwd, hosts, group, and services

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anacron

Like cron, but looks to see if it has been AT LEAST a certain time since the last time the job was run.

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anacron -f

Forces execution of all jobs

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anacron -u

Updates the timestamps of all jobs to current time but does not actually run any

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anacron -n

Run all jobs immediately

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anacron -t

Use the specified file rather than /etc/anacrontab

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Can regular users use anacron?

no!

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anacron syntax

period_in_days delay_in_minutes
job_identifier
command

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who -b

time of last system boot

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who -l

print system login processes

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who -q

count all login names and number of users logged in

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who -u

list logged in users and process id/comment

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who -H

print column headers

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who -a

print all info

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fuser

Display the PIDs of processes using the specified files or file systems

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fuser -k

Kills all processes accessing a file

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fuser -i

interactive mode

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fuser -v

verbose

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fuser -u

append username

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fuser -a

display all filenames

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w -i

display ip addresses instead of hostnames

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last -n

show specific number of lines

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last -R

suppress hostname

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last -F

Print full login and logout times and dates

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last -x

Display the system shutdown entries and run level changes

What order do the bash and profile configuration files execute?

/etc/profile ~/.bash_profile ~/.bashrc /etc/bashrc

Non-login shell will only execute...

/etc/bashrc | ~/.bashrc

Ways to switch to root using login shell

su - su --login su -l

exec

Replaces the current shell process with the specified command

logrotate configuration file

/etc/logrotate.conf

In logrotate.conf, compress

compress old version of files with gzip

In logrotate.conf, rotate

files are rotated the specified amount of times before being removed or mailed

In logrotate.conf, size

Log will be rotated once it reaches a certain size

In logrotate.conf, prerotate

Lines between prerotate and endscript are executed before the log file is rotated

In logrotate.conf, postrotate

Lines between postrotate and endscript are executed after the log file is rotated

In logrotate.conf, sharedscripts

Makes prerotate and postrotate scripts run only once (prerotate before any of them start and postrotate after all have rotated)

In logrotate.conf, create

Immediately after rotation the log file is created with the same name as the log file just rotated

journalctl

Without parameters will show the full contents of the journal starting with the oldest entry

journalctl -n

Show the specified number of lines

journalctl -k journal --dmesg

show only kernel messages

By default the journal data is stored in _______

/run/log/journal This is temporary storage, cleared at reboot

journalctl _SYSTEMD_UNIT=httpd.service

Show entries pertaining to httpd.service

dig @8.8.8.8 domainname.com

Use 8.8.8.8 as the nameserver for the lookup

host -4 host -6

Force IPv4 or IPv6

host google.com 8.8.8.8

Use 8.8.8.8 as the name server for the host command

System provided configuration files for lightdm

/usr/share/lightdm/lightdm.conf.d/*.conf

Configuration files you can edit to override lightdm settings

/etc/lightdm/lightdm.conf.d/*.conf or /etc/lightdm/lightdm.conf

How to disable booting into a graphical user interface

Edit /etc/default/grub and set | GRUB_CMDLINE_LINUX="text"

GRUB default configuration file

/etc/default/grub

How to disable guest login

allow-guest=false

How to hide the user list

greeter-hide-users=true

How to allow manual login

greeter-show-manual-login=true

How to set automatic login

autologin-user=username | autologin-user-timeout=delay

Used to test a network service that's behaving oddly

nc -z

specifies that nc should just scan for listening daemons without sending any data to them

nc -l

binds to a specific port to listen for incoming connections

nc -vz localhost 22

runs netcat on localhost port 22

traceroute -n

Do not map IP address to host names when displaying them

traceroute -p

Specify port number

tracepath

show the route to a destination and discovers MTU

/etc/hostname

File where the hostname is stored

In /etc/resolv.conf, domain server.com

Use server.com for short searches

In /etc/resolv.conf, search server.com

Will make it so that test.server.com will work just by accessing "test"

netstat -P

show the PID and name of the program to which each socket belongs

netstat -i

Display interface information

netstat -r

Display routing table information

netstat -M

Information about IP/NAT Linux masquerade

netstat -a

Display all info

netstat -n

Do not resolve to hostnames