2015 Updates Flashcards
getent
- Displays entries from databases configured in /etc/nsswitch.conf
- Most commonly used to query passwd, hosts, group, and services
anacron
Like cron, but looks to see if it has been AT LEAST a certain time since the last time the job was run.
anacron -f
Forces execution of all jobs
anacron -u
Updates the timestamps of all jobs to current time but does not actually run any
anacron -n
Run all jobs immediately
anacron -t
Use the specified file rather than /etc/anacrontab
Can regular users use anacron?
no!
anacron syntax
period_in_days delay_in_minutes
job_identifier
command
who -b
time of last system boot
who -l
print system login processes
who -q
count all login names and number of users logged in
who -u
list logged in users and process id/comment
who -H
print column headers
who -a
print all info
fuser
Display the PIDs of processes using the specified files or file systems
fuser -k
Kills all processes accessing a file
fuser -i
interactive mode
fuser -v
verbose
fuser -u
append username
fuser -a
display all filenames
w -i
display ip addresses instead of hostnames
last -n
show specific number of lines
last -R
suppress hostname
last -F
Print full login and logout times and dates
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
nc
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
