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Fall 2024 > 9 Services > Flashcards

9 Services Flashcards

1
Q

services

A

interactive programs run in the background users can interact with

ex: web service users can interact with

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2
Q

daemons

A

noninteractive programs running on the system and don’t communicate with users

ex: httpd is required to make web service run

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3
Q

what is systemd?

A

software suit that provides an init method/daemon

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4
Q

improvements over SysVinit

A

support parallelization (starting programs at the same time). us Control Groups (cgroups) instead of PID for petter categorization and isolation

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5
Q

systemd service commands of systemctl

systemctl {subcommand} {service}

A

start
stop
restart
enable
disable
status
mask -creates a sym link to /dev/null to prevent starting service

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6
Q

unit vs unit files

A

the term unit describes a resource systemd knows how to manage

unit file defines how the unit must be manages by systemd

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7
Q

/lib/systemd/system

A

house default unit files

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8
Q

/etc/systemd/system

A

configurations managed here and changes to these files override settings default unit settings in /lib but it doesn’t overwrite the file with new configurations

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9
Q

.service files directives

A

Before=
-this will start before any unit in this field
After=
-when multiple units are specified, this unit will start after any unit listed
Requires=
-Units listed will be started if possible, and the primary unit will fail if the units specified by Requires= fail to start
Wants=
-Units listed will be started if possible, but the primary unit will still launch even if the units specified by Wants= fail to start
Type=
-Configures the startup type for the service; Values include simple, exec, forking, oneshot, dbus, notify, and idle
User=
-Specifies the user under whose authority the service runs (usually root)
ExecStart=
-Executes commands along a specified absolute path upon startup to start a service
ExecStop=
-Executes commands along a specified absolute path upon shutdown to stop a service

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10
Q

Timer unit files directives

A

OnBootSec - (monotonic) time spanning from an even such as system startup
OnCalender - (realtime) time referenced from system clock

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11
Q

OnCalender format for timer unit files

A

{day of the week: Fri} (Year-Month-Day) (Hour:Min:Sec) –>

  • --* ::*

*/ in a field of {clock time} - specifies whenever this amount of time passes (not the time of day) in clocks field containing this, the value associated and what after matches value execute
ex: :/30:00
in the minute field and associated value is 30 so at least every 30 min, and whatever is after

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12
Q

.mount unit files options

A

What=
-Absolute path to storage to mount
Where=
-Absolute path to mount point directory
Type=
-Define the filesystem type (optional)
Options=
-Any additional required options for the mount action

systemd unit files use dashes as a delimiter for paths when read

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13
Q

common .target unit files

A

default -The target to which the system boots by default

multi-user.target - Starts the enable services and the system to the CLI

graphical.target - Starts the enable services and the system to the GUI

network-online - Starts the specified network services, and delays the target until network service is established

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14
Q

systemctl get-default

A

display default target

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15
Q

systemctl isolate {graphical | multi-user}.target

A

swap system to graphical or multi-user target.

temporary?

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16
Q

/etc/rsyslog.conf

A

main rsyslog configurations file

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17
Q

/etc/rsyslog.d/50-default.conf

A

additional configurations r syslog file

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18
Q

cron.error -/var/log/cron

A

logs all cron messages from error and upwards to /var/log/cron

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19
Q

/var/log/syslog
/var/log/messages

A

general system logs for 1. Debian 2. Red hat derivatives

Log location for rsyslog daemon

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20
Q

/var/log/auth.log
/var/log/secure

A

authentication logs for 1. Debian 2. Red Hat derivatives

21
Q

/var/log/yum.log

A

logs YUM package management

22
Q

/var/log/httpd

A

dir for Apache webserver log information

23
Q

how to make a centralized server for rsyslogs where other servers will forward

A
  1. uncomment lines in the /etc/rsyslog.conf on the central server
    # Provides UDP syslog reception
    $ModLoad imudp.so
    $UDPServerRun 514
  2. configure a template to organize the storage of inbound logs
    $template DynamicFile,”/var/log/%HOSTNAME%/forwarded-logs.log” . -?DynamicFile
  3. configure firewall to accept inbound connections over port 514/udp

-On the forwarding server, edit the /etc/rsyslog.conf file and add the following line to the Rules section: . @IP
-Where IP is the IP
-address of the
-destination log
-storage server.
-Restart the rsyslogd on both servers.

  1. On forwarding server, type “ logger TEST “and search /var/log for a dir of the forwarding server and an entry
24
Q

Configure network time NTPd (daemon)

older service

A

synchronizes system time against 1 more more specified time servers over port 123/udp.
Configure: define time servers by editing /etc/ntp.conf
- add “server
{timeserver-IP-
address}” entry

restart service

25
Q

when is chrony better than ntpd

A

when Linux deployments lack constant or consistent network connections, time cant be accurately or immediately synchronized time settings.

26
Q

Configure chrony

latest service

A

Uses port 123/udp
edit chrony configuration file /etc/chrony.conf

view detail configs, status, and sync info with:
chronyc -n tracking
chronyc activity

27
Q

cron jobs

A

primary Linux schedular is cron. the tool references a crontab file to determine if a task has been assigned.
cron jobs can be used to specify tasks each min, hr, day, month, week day.

28
Q

cron date format

A

” * * * * * <cmd> "</cmd>

  • min (0 - 59)
  • hour (0 - 23)
  • day of month (1 - 31)
  • month (1 - 12)
    *day of week (0 - 6)
29
Q

/etc/crontab

A

system wide crontab file

30
Q

/var/spool/cron/crontabs

A

a per-use crontab

31
Q

crontab -e

crontab [options]

A

like visudo - its the formal way to edit the cron daemon. cron configurations rely on crontab file

Editing the file is used to schedule events

32
Q

at cmd

at [options] {time}

A

runs a task once at the specified time. flexible as it can be specify a date and time or to run after a given time period.

used in an interactive manner where “ at {time} “ once executed with pop and interactive menu to specify task.
- Ctrl + D exits

can be used noninteractively by piping “at {time}”
ex: echo “Hi” | at 3 pm

time arguments excepts:
-noon -12:00 p.m.
-teatime - 4:00 p.m.
-midnight - 12:00 a.m.
-now + # {minutes | hour} - time # {min | hr} from now

33
Q

crony vs at

A

cron scheduling executes at every occurrence of date/time .
at only executes task once and must be made against with the same command to execute similar task

34
Q

what other files can schedule events

A

systemd .timer files from unit files:
/etc/systemd/system

35
Q

configure an Apache web server

A
  1. edit /etc/httpd/conf/httpd.conf file.
    -find Listen and add
    next to it {localhost
    | 127.0.0.1}:80
    ex: Listen localhost:80
    -find DocumentRoot
    and add
    “/var/www/html”
    next to it like Listen
    ex: DocumentRoot “/var/www/html”

indicates to listens for connections to itself over port 80 and where the file that make up the website are found

  1. configure firewall to permit inbound http connections (80/tcp)
    firewall-cmd
    –permanent
    –zone=public
    –add-service=http
    ^(all one line)

firewall-cmd –reload

  1. use a text editor to create a simple test web page and save as index.html
    note: rename old
    index file
  2. change ownership and grp of the file to Apache

chown apache:apache /var/www/html/index.html

  1. enable and start/restart service

systemctl enable httpd
systemctl {start | restart} httpd

  1. launch browser to display webpage

firefox http://localhost

36
Q

configure NFS

permits file sharing and accessing over the network from a central server

A
  1. deploy NFS server and install, enable, and start service.

systemctl enable nfs-server
systemctl start nfs-server

  1. create or select directories on file server that should be shared/exported over network. note these and possible required permissions
  2. Edit /etc/exports file to make these resources available over network
    -must use absolute
    path

ex:
{(dir | file) path} {Network ID/CIDR} ({privileges - symbolic}, sync)
the dir/file will be available to clients connecting from that subnet and have specified privileges

{(dir | file) path} *(ro, sync)

the dir/file can be accessible from any client IP, the “ro” permission specifies read-only (optional)

  1. restart service
  2. might need to configure firewalls for NFS connections: 111/tcp (and udp) plus 2049/tcp (and /udp)
37
Q

Configure NFS clients

A
  1. display available directories on remote file server

showmount -e {remote -server-IP-address}

  1. on client, mount exported dir to a local mount point can create subdir int /mnt for nfs-share

mount -t nfs4 {remote-server-IP}:{NFS dir | file} {mount-point}

can mount -t samba2 work?

38
Q

CUPS

A

print management system for Linux enable a computer to be a print server. CUPS host can initiate client print jobs.

it can process different data formats on the same server.

39
Q

How to manage CUPS?

A

provides a web-based interface for configuring the service .

40
Q

/etc/cups/cupsd.conf
/etc/cups/cups-files.conf

A

CUPS configuration files that the provided CUPS web-based interface modifies

41
Q

CUPS configuration

A
  1. install service and start
    systemctl enable cups
    system start cups
  2. open fire wall to CUPS port 631/tcp
  3. management interface is access from web:
    http://localhost:631
42
Q

what is lpr

A

submits files via the command line for printing, and are sent to a default printer unless specified a printer to print or queue.

43
Q

lpr options cmd -E -P {destination}
-# {copies} -T {name} -l -o {options} -p -r

lpr [options] {file}

A

-E - force encryption

-P {destination} - specify printer

-# {copies} - copies 1-100

-T {name} - set job name

-o {option} set job option like landscape mode, scale output, double-sided etc.

-p print specified files with shaded header including date, time, job name, page #

-r printed files should be deleted after printing

44
Q

lpq cmd

A

display existing print jobs a printer is managing

45
Q

date cmd and options

A

print date in specified format

formation date is an argument with with preceding “+”
ex: date +[argument]

  • %A - Display the full weekday name.
    -%B - Display the full month name.
    -%F - Display the date in YYYY-MM-DD format.
    -%H - Display the hour in 24-hour format.
    -%I - Display the hour in 12-hour format.
    -%j - Display the day of the year.
    -%S - Display seconds.
    -%V - Display the week of the year.
    -%x - Display the date representation based on the locale.
    -%X - Display the time representation based on the locale.
    -%Y - Display the year.
46
Q

/etc/localtime

A

maintains date of system
format: <day><month><day><24 hour time ##:##:##> <time> <year></year></time></day></month></day>

47
Q

change systems date

A

date -s

48
Q

timedatectl cmd

timedate [option] [subcommand]

A

set system date and time info

subcommand:
status - show current settings
restart - sync local (system) clock base on hardware
list-timezones
set-timezones {time-zone}
ex: timedatectl set-timezone
“America/Denver”
set-time {HH:MM:SS}

options:
-H execute on remote host specified by IP or hostname
–no-ask-password prevent user being asked to authenticate when performing a priv task
–adjust-system-clock sync system clock to real-time clock
-M {local container} execute on local container

49
Q

/usr/share/zoneinfo/

A

store regional time zones and can use to trouble shoot.
they are special files and to change time zone, create a sym link to on of the time zones in /etc/localtime file

Fall 2024 (4 decks)

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