Ubuntu Server Overview

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title
Ubuntu Server Overview Training Course
author
Lukasz Sokolowski


Ubuntu Server Overview

Ubuntu Server Overview Training Materials

Introduction ⌘

  • Overview
  • Installation
  • Ubuntu Server Edition
  • Ubuntu and Hardware
  • Package Management

Overview ⌘

Ubuntu

  • For all people - usable even by disabled (anyhow)
  • Connects people (opensource) - no matter what race, age, path, etc
  • So my modified custom version of it's logo is.. (-;

Overview Con't - ..like that! ⌘

UbuServ.png

Installation ⌘

  • Instant Ubuntu VMs
    • multipass.run
      • cloud-init.io
  • Manual
  • Automated
    • maas.io

Ubuntu Server Edition ⌘

  • Ubuntu versions
  • Available support
  • LTS vs standard edition
  • Maintenance policy and life cycle

Ubuntu versions ⌘

  • Every Oct and Apr, each year
  • Funny codenames: Focal, Beaver, Tahr, etc
  • Every 2y, stable and long support ver(for 5y)
  • Choice between long-stable and features-full

Available support ⌘

  • features-full - ATM: 21.04 and 21.10
    • standard 9 months, no long-term, same EoL(9m)
  • long-stable - ATM: 20.04.x, 18.04.x, 16.04.x, 14.04.x
    • Long-Term Support 5y, EoL for 10y

LTS and standard edition ⌘

  • Releases
    • wiki.ubuntu.com/Releases
  • ESM - Extended Security Maintenance
    • Extendable subscription
    • for LTS only, for 5y - free(private) or paid(enterprise)
    • ubuntu.com/advantage

Maintenance policy and life cycle ⌘

  • $ ua status
  • debs, snaps, images, containers
  • Version cycle
    • ubuntu.com/about/release-cycle

Ubuntu and Hardware ⌘

  • Checking compatibility with Ubuntu
  • Available kernels and supported architectures

Checking compatibility with Ubuntu ⌘

  • follows the requirements of the Linux kernel and the GNU tool-sets
  • wiki.ubuntu.com/HardwareSupport
  • ubuntu.com/certified
  • wiki.ubuntu.com/Hardware_probe
    • hwinfo, hw-probe, hwdata
    • sudo -E hw-probe -all -upload
  • $ discover

Available kernels and supported architectures ⌘

UbuSuppArch.png

  • help.ubuntu.com/lts/installation-guide/s390x/ch02s01.html

Package Management ⌘

  • Dpkg VS apt-get VS snap(snapcraft.io)
  • Available sources
  • Adding new sources
  • Alternative packet management systems (RPM, Yums, etc...) and dependencies
  • Aptitude
  • Automatic Updates
  • Distribution Upgrades

Examples ⌘

# 'dpkg' VS 'apt' (or apt-get) VS 'snap'
sudo apt install mc
sudo snap install hello
sudo dpkg -i package_name.deb

# updating the index of packages
sudo apt update

# upgrading packages
sudo apt upgrade

# removing
sudo apt remove subversion*

# aptitude - menu-driven text-based front-end to 'apt'
sudo aptitude

Exercises ⌘

Install

  1. MariaDB via 'apt' command
  2. postgresql with 'snap'
  3. with 'dpkg' add nodejs

Sources ⌘

  • Main - /etc/apt/sources.list
  • Custom - /etc/apt/sources.list.d
  • Adding new - manually, via commands
    • mongoDB example
# Import the public key
wget -qO - https://www.mongodb.org/static/pgp/server-5.0.asc | sudo apt-key add -

# Creates a list file
echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/5.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-5.0.list

# Refreshing the list
sudo apt update

RPM, Yum, etc

"Yes we can" - but don't!

  • Doable but can have serious dependency issues
  • It is always better to do it from sources instead and then make a deb package
    • packaging.ubuntu.com/html/packaging-new-software.html

Automatic Updates ⌘

  • If installed via snap - enabled by default (but slower run and separated form the rest of the server)
  • sudo apt install unattended-upgrades
    • Config - /etc/apt/apt.conf.d/50unattended-upgrades
    • Enabling - /etc/apt/apt.conf.d/20auto-upgrades
  • Automatic email when updates available - sudo apt install apticron
    • Config - /etc/apticron/apticron.conf

Distro Upgrades ⌘

  • To go for the next big ver, especially LTS
    • sudo do-release-upgrade
    • we should do it at least once in 5y, before the end of support for LTS
  • To fully update existing release
    • sudo apt-get dist-upgrade
    • might be helpful, but does remove or install new things
    • will be called by do-release-upgrade

Networking ⌘

  • Network Configuration
  • TCP/IP, IPv4 and IPv6
  • Dynamic Host Configuration Protocol (DHCP) - server
  • Time Synchronisation with NTP - depricated
  • DPDK

Network Configuration ⌘

  • Ethernet Interfaces - eno1, enp0s25 or kernel style eth#
    • $ ip a
    • $ sudo lshw -class network
    • netplan config - match, set-name keys
      • $ netplan info; netplan get all
    • $ sudo ethtool eth3

IP Addressing ⌘

  • Temporary assignment - ip command
    • $ sudo ip addr add 10.102.66.200/24 dev enp0s25; ip link set dev enp0s25 up/down
  • via DHCP or static IP
    • use netplan config file and then $ sudo netplan apply

Name Resolution ⌘

  • DNS Client Configuration - symlink with netplan
    • /etc/resolv.conf -> ../run/systemd/resolve/stub-resolv.conf
  • Static Hostnames - /etc/hosts
  • Name Service Switch Configuration - /etc/nsswitch.conf
  • Bridging - more advanced config, bridges: in /etc/netplan
    • scenario1 - setting up a bridge with multiple network interfaces, then using a firewall to filter traffic between two network segments
    • scenario2 - using bridge on a system with one interface to allow virtual machines direct access to the outside network
  • networkd-dispatcher - for pre-up, post-up, etc. hook scripts
    • netplan doesn't support hooks by deafult, like it was with ifupdown

DHCP server ⌘

  • Configuration
    • Manual allocation (MAC address)
    • Dynamic allocation (address pool) - from scope(range)
    • Automatic allocation - permanent assignment
  • $ sudo apt install isc-dhcp-server
  • Important related files
    • /etc/dhcp/dhcpd.conf
    • /etc/default/isc-dhcp-server

Time sync ⌘

  • timedatectl or timesyncd - they are part of systemd
  • also chrony - chronyd and chronyc
    • supports GPSD
      • gpsd.gitlab.io/gpsd/hardware.html
    • support for NTS(Network Time Security)

DPDK ⌘

  • Data Plane Development Kit
  • libraries and drivers for fast packet processing
  • provide the EAL(Environment Abstraction Layer)
  • hides the details of the environment and provides a standard programming interface
  • Common use cases
    • special solutions for instance network function virtualization
    • advanced high-throughput network switching
  • OpenVswitch-DPDK - built in client lib (openvswitch-switch-dpdk)

Remote Administration ⌘

  • OpenSSH Server
  • OpenLDAP Server
  • Samba and LDAP
  • Kerberos

OpenSSH Server ⌘

Tools for the remote control of networked computers and transfer of data between

  • replaced insecured telnet and rcp
  • ssh client calls sshd server via authenticated session
  • secure and encrypted connection - plain passw, public key, Kerberos tickets
  • clients: ssh, scp, etc
  • packages: openssh-client, openssh-server
  • configs: /etc/ssh/sshd_config
  • commands: ssh-keygen -t rsa -b 4096 ; ssh-copy-id username@remotehost ; ssh-import-id <username-on-remote-service>

OpenLDAP Server ⌘

Lightweight Directory Access Protocol

  • for querying and modifying a X.500-based directory service running over TCP/IP
  • Accesses directories
    • directory - tree of data entries (DIT)
    • entry - set of attributes, has unique identifier(DN)
      • DN is based on RDN and it's parent entry's DN
    • attribute - key and value(s), defined in objectClass(special attr)
    • schema - consists of attrs and objectClasses
  • Main config files: /etc/ldap/slapd.d ; /etc/ldap/schema
  • Commands: ldapwhoami ; ldapadd ; ldapsearch ; ldappasswd ; ldapmodify
  • Additional configs: add_content.ldif ; uid_index.ldif ; logging.ldif ; changerootpw.ldif

Samba and LDAP ⌘

  • Samba 4 is best integrated with its own LDAP server in AD mode
  • The NT4 mode - deprecated

More about Samba - later on.. (-;

Kerberos ⌘

Network authentication system based on the principal of a trusted third party

  • Principal - users, computers, and services provided by servers
  • Instances - service and special administrative principals
  • Realms - domain or group our hosts and users belong to, uppercase, defult is DNS domain
  • Key Distribution Center(KDC) - database, authentication, ticket granting; each realm >= 1 KDC
  • Ticket Granting Ticket(TGT) - issued by the Authentication Server(AS), encrypted in user’s passw
  • Ticket Granting Server(TGS) - issues service tickets to clients upon request
  • Tickets - confirm the identity of user and service requested by the user
  • Keytab Files - extracted from the KDC db, contain the encryption key for a service or host

Domain Name Service (DNS) ⌘

  • Maps IPs with FQDN(fully qualified domain names)
  • Configuration - name server
    • $ sudo apt install bind9 dnsutils
    • Common cases: caching nameserver, primary server, secondary server
      • Can be all of them in the same time
    • Config files
      • global DNS options - /etc/bind/named.conf.options
      • for our zones - /etc/bind/named.conf.local
      • default (localhost, its reverse, root hints) - /etc/bind/named.conf.default-zones
  • More here: ubuntu.com/server/docs/service-domain-name-service-dns

Security ⌘

  • User Management
  • Console Security
  • Firewall
  • AppArmor
  • Certificates
  • OpenVPN
  • SSSD

User Management ⌘

  • root disabled by default
    • enabling - $ sudo passwd
  • sudo - accountability, granular control
    • group sudo, config /etc/sudoers
  • Commands: adduser ; deluser ; chown ; chmod ; passwd ; addgroup ; delgroup
  • Files: /home/username ; /etc/skel ; /etc/passwd ; /etc/group
  • Remove/rename /home/username/.ssh/authorized_keys
  • External user db auth - centralized (ldap, openid, cas, etc)
  • Good password

Good password ⌘

  • $ chage -l username
    • min passw lenght
    • passw expiration
    • periodically forcing to change passw
  • Good passw - Exercise

Console Security ⌘

  • dis ctrl+alt+del
    • $ sudo systemctl mask ctrl-alt-del.target ; sudo systemctl daemon-reload
  • ssh captcha - libpam-captcha
    • extensions - sentry over fail2ban(denyhosts, sshblacklist, etc)

Firewall ⌘

  • Netfilter subsystem from Linux kernel
    • managed with iptables
  • Frontend tools can simplify it
    • ufw - simple firewall config tool
  • IP masquerading - private machine can access Internet through masquerade-machine
    • doable via both: iptables and ufw
  • Other tools - shorewall (advanced firewall)
  • Logs - rules must come before terminating

AppArmor ⌘

  • Linux Security Module implementation of name-based mandatory access controls
  • installed and loaded by default
  • uses profiles of an application to determine what files and permissions the application requires
  • some packages will install their own profiles
  • additional apparmor-profiles package

Certificates ⌘

  • public-key cryptography
  • public key encrypts, private key decrypts
  • app traffic - with SSL(Secure Socket Layer) or TLS(Transport Layer Security)
  • Example - apache with https
  • Certificate - distributes public key and org
    • digitally signed by CA(Certification Authority)
    • self-signed (not recommended for prod envi)
  • tools: openssl
    • $ openssl genrsa -des3 -out server.key 2048

OpenVPN ⌘

  • Virtual Private Networking (VPN)
  • flexible, reliable and secure - originates from SSL/TLS VPN stacks
  • Allows to set up a Public Key Infrastructure (PKI)
    • uses SSL/TLS certificates for authentication
    • and key exchange between the VPN server and clients
  • routed or bridged VPN mode
  • uses either UDP or TCP, default port 1194 (configurable) covers all communication
  • support for all systems - Lin distros, OS X, Win, OpenWRT based WLAN routers, etc

SSSD ⌘

  • System Security Services Daemon
  • Collection of daemons that handle:
    • authentication, authorization, and user and group information from a variety of network sources
  • Its core supports - Active Directory, LDAP, Kerberos
  • Provides PAM and NSS modules to integrate remote sources
  • Allows remote users to login and be recognized as valid users, including group membership
  • Allow for disconnected operation - cached when network failure, etc

Web Servers ⌘

  • HTTPD - Apache2 Web Server
    • LAMP - Linux, Apache, MySQL, Perl/Python/PHP
  • Apache extensions like Tomcat, Kafka, etc
  • PHP(5/7/8) - Scripting Language
    • ATM, php8.1 - faster, more reliable, plenty of features (like JIT, Union Types, etc)
  • Squid - Proxy Server
    • full-featured web proxy cache server app
    • caching SSL, DNS lookups, transparent caching
    • caching protocols - ICP, HTCP, CARP, WCCP
  • Ruby on Rails - open source web framework
    • for developing database backed web applications
    • optimized for sustainable productivity of the programmer
    • lets the programmer to write code by favouring convention over configuration
  • Nodejs based stacks like MEAN or MERN

Databases ⌘

  • MySQL, MariaDB
  • PostgreSQL

MySQL, MariaDB ⌘

  • Fast, multi-threaded, multi-user, and robust db server
  • Preferred for higher performance requirements
  • Intended for mission-critical, heavy-load production systems and mass-deployed software
  • Oracle took MySQL - here came MariaDB (-;
    • Even faster, more performant and fully open-source
  • DB engines - transparent to the end user
    • MyISAM - fulltext data type, favours read-only workload, lacks journaling, locking only whole table
    • InnoDB - ACID compliant, reliable transactions, locking on row level, journaled(more reliable data recovery)
  • Commands: mysgl ; mysqld ; mysqldump ; mysqltuner

PostgreSQL ⌘

  • Preferred for its attention to standards conformance, features, and extensibility
  • Hybrid of relational and OOP approaches
  • Streaming Replication
    • continuously ships and applies the WAL XLOG records (Write-Ahead Log)
    • keeps standby servers current
  • Commands: psql ; postgresql
  • Package with docs: postgresql-doc-12

Wiki Applications ⌘

  • Moin Moin
    • advanced, easy to use and extensible WikiEngine with a large community of users
    • it is about collaboration on easily editable web pages
  • MediaWiki
    • php based collaboration and documentation platform
    • powers Wikipedia and thousands of other websites, companies and organizations
    • uses simple markup language - yet stil supports pure html

File Servers ⌘

  • FTP Server
    • downloading files between computers
    • also uploading, but insecure - depricated
  • Network File System (NFS)
    • allows a system to share directories and files with others over a network
    • locals use less disk space, same home dir on all machines, less removable medias
  • CUPS - Print Server
    • Common UNIX Printing System - freely available, portable printing layer
    • uses Internet Printing Protocol (IPP), while supports large range of printers
    • supports PostScript Printer Description (PPD) and auto-detection of network printers

Email Services ⌘

  • Postfix
    • default Mail Transfer Agent (MTA) in Ubuntu
    • fast and secure, with flexibility in administration, compatible with the MTA sendmail
  • Exim4
    • Message Transfer Agent (MTA) developed at the University of Cambridge
    • originally for Unix, can be installed in place of sendmail
  • Dovecot Server
    • Mail Delivery Agent, written with security primarily in mind
    • It supports the major mailbox formats: mbox or Maildir, serves as IMAP or POP3
  • Mailman
    • open source program for managing electronic mail discussions and e-newsletter lists
    • powerful, easy to install and maintain - all the Ubuntu mailing lists are using it
  • Mail Filtering - modules like dovecot-sieve, dovecot-antispam

Version Control System ⌘

  • Bazaar - free software sponsored by Canonical
    • doc.bazaar.canonical.com/migration/en/why-switch-to-bazaar.html
  • Subversion - based on CVS, improved a lot, centralized
    • subversion.apache.org
  • CVS Server - good(?) old grandpa (-;
  • Mercurial - like git, but with more freedom (-:
    • www.mercurial-scm.org
  • GIT - "the stupid content tracker"
    • distributed, fast, efficient, compressed

Windows Networking ⌘

Sharing network resources with Windows computers

  • Samba File Server
    • Facilitates sharing of files, folders, volumes
  • Samba Print Server
    • extends CUPS to share printers with Win cli
  • Securing a Samba File and Print Server
    • Identifying via file permissions, group policies, Kerberos authentication service
    • needs additional package - libpam-winbind
  • Samba as a Domain Controller - configured to appear as a WinNT4-style
    • centralizes user and machine credentials, can work as PDC or BDC
  • Samba Active Directory Integration
    • Sharing vital information about the computers and users of the network - LDAP, MAD
  • Likewise Open - old, depricated, insecure

Backups ⌘

  • Shell Scripts
    • Archive Rotation
  • Bacula
  • Rsnapshot

Shell Scripts ⌘

  • File - backup.sh
    • $ tar czf "/mnt/backup/$hostname-$day.tgz" "/home /var/spool/mail /etc /root /boot /opt"
    • $ chmod u+x backup.sh
    • one time - $ sudo ./backup.sh
    • periodically - $ sudo crontab -e 
      • # m h dom mon dow   command
0 0 * * * bash /usr/local/bin/backup.sh
    • restoring - $ cd / ; sudo tar -xzvf /mnt/backup/host-Monday.tgz
  • Archive Rotation
    • Rotating NFS Archives - grandfather-father-son rotation scheme (monthly-weekly-daily)

Bacula ⌘

  • Backup, restore, and verify data across our network
  • Cross-platform, supports - Lin, Win, MacOS
  • Several components and services involved
    • Director - main service, controls all the rest
    • Console - pure text and GUI
    • File(Client) - on each backed up machine, unswers to Director
    • Storage - storage and recovery of data to the physical media
    • Catalog - maintaining the file indexes and volume databases
    • Monitor(only GUI so far) - monitoring of the Director, File and Storage daemons

Rsnapshot ⌘

  • rsync-based filesystem snapshot utility
  • incremental and scheduled backups of local and remote filesystems
  • extensive use of hard links - low disk space used
  • when remotely - needs SSH without password (OpenSSH)

Virtualization and Cloud Computing ⌘

  • libvirt
  • JeOS and vmbuilder - depricated, EoL
    • packer.io - an alternative
  • Quemu and KVM
  • VirtualBox
  • VMware
  • EC2
  • Containers - lxd, lxc
  • Eucalyptus - old, replaced with OpenStack

libvirt ⌘

  • Used to interface with different virtualization technologies
  • kvm-ok - checks if our hardware supports the necessary virtualization extensions for KVM
  • Virtual Machine Management - virsh, multipass, uvt, virt-*, openstack
    • system and session scope
    • migration - offline, live, postcopy
    • Device Passthrough vs Hotplug
    • can access Qemu monitor
    • Huge Pages - allocation, usage
    • Apparmor isolation
    • Sharing files between Host <=> Guest

Quemu and KVM ⌘

  • machine emulator
    • can run operating systems and programs for one machine on a different machine
  • Mostly used as virtualizer with KVM kernel components
  • utilizes the virtualization technology of the hardware to virtualize guests
  • Upgrading the machine type
  • Usage for microvms

VirtualBox ⌘

x86 and AMD64/Intel64 virtualization - enterprise and home use

  • lots of features
    • backed by Oracle and huge community
  • high performance
  • open source via GPL2
  • runs on Win, Lin, Mac, Sol
    • offers guests in above and also OS/2, OpenBSD
  • guest-additions (mostly for GUIs)

VMware ⌘

Not only virtualization

  • Platform for applications
  • multi-cloud (Telco, etc)
  • Networking, security
  • Workspace - any-*

EC2 ⌘

Amazon Elastic Compute Cloud (Amazon EC2)

  • humongous web service, mostly for developers
  • provides secure, resizable compute capacity in the cloud
    • complete control of computing resources
  • supports macOS
  • Intel, AMD, and Arm-based processors
  • ATM: 25 regions and 81 availability zones globally

Containers - lxd, lxc ⌘

  • lxd - like libvirt
    • lightervisor - lightweight container hypervisor
    • creates and administers "containers" on a local system
    • LXD API deals with ‘remotes’
      • uses LXC under the covers
    • commands: lxd init ; lxc launch ; lxc image list(info) ; lxc exec ; lxc config ; lxc-remote
  • lxc - like QEMU
    • Containers are a lightweight virtualization - an enhanced chroot, no full virtualization
    • Do not emulate hardware, share the same operating system as the host
    • similar to Solaris zones or BSD jails
    • implementations in Linux - vserver and OpenVZ ("fathers" of containers)
    • commands: lxc-create ; lxc-ls ; lxc-start(stop) ; lxc-info ; lxc-destroy ; lxc-attach

Other ⌘

  • Keeping /etc under Version Control System
  • Block Device Replication

Tools ⌘

  • byobu
  • etckeeper
  • munin
  • nagios
  • pam_motd
  • Puppet

Byobu ⌘

  • xterm multiplexor
    • acts as a wrapper to screen or tmux(default)
  • multiple shells in one terminal
  • more user-friendly

etckeeper ⌘

  • industry best practice
  • stores the contents of /etc in VCS repo (default is GIT)
  • integrates with APT
    • automatic commits of changes in packages
sudo apt install etckeeper

munin ⌘

  • networked resource monitoring tool
  • helps analyze resource trends and performance issues
  • plug and play
  • no need to configure - default inst. provides a lot of graphs

nagios ⌘

Monitoring of

  • Network
    • overloaded data links or network connections, routers, switches, etc
    • availability, uptime and response time - all in a variety of visual representations and reports
  • Server - for Win and Lin
    • supports agent-based and agentless monitoring
    • above 5000 different addons from community
  • Application - Win, Lin, UNIX, Web
    • detects application, service, or process problems
    • takes action to eliminate downtime for our application users

pam_motd ⌘

After logging shows the informative Message Of The Day (MOTD)

  • landscape-common - displaying core system data: cpu, memory, disk space, etc
  • update-notifier-common - available package updates, impending filesystem checks (fsck), and required reboots
  • weather-util, etc

Puppet ⌘

  • cross platform framework enabling system admins to perform common tasks using code
    • installing new software, checking file permissions, updating user accounts, etc
  • Useful during the initial inst. of a system, also throughout the system’s entire life cycle
  • Mostly used in a client/server configuration

Block Device Replication ⌘

Ubuntu HA - DRBD

  • Distributed Replicated Block Device (DRBD)
  • mirrors block devices between multiple hosts
  • transparent to other applications
  • Mirrors - any block device hard disks, partitions, RAID devices, logical volumes, etc
sudo apt install drbd8-utils

THE END ⌘

Summary - Ubuntu

  • Try it and have fun! (-;
  • Enjoy the fearless world of debian-based distro
    • Stable, safe and yet modern system
  • For PL-guys check: ubuntu.pl

Resources

Based on (mostly):

  • ubuntu.com/server/docs
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