Index

Numbers and Symbols

  • / filesystem, 200
  • 128-bit message digests, 60

A

  • acceleration, linear, input devices, 107
  • AccelerationProfile, input devices, 107
  • accessibility
    • GRUB beep for input, 116
    • key presses, 119
    • legacy utilities, 111
    • Orca, 112
    • screen magnifier, 116
    • speech recognition, KDE, 114
    • Ubuntu, 209
  • account information, 178
  • accounts
  • addresses
    • IPv6, 161, 170
    • local, IPv6 pings, 165
    • private, internal use, 160
  • administrative tasks, 124–138, 257–263
  • aliased commands, 90
  • aliases, missing, 98
  • anacron, 129
  • Apache, /var/log/httpd/access.log, 53
  • appending files, 61
  • applications, containerization versus virtualization, 35
  • apt-cache, Debian, package lists, 38
  • architecture, system, 3–20, 220–226
  • ARP, disabling, 170
  • arp, IP address-to-Mac address pair, 168
  • arrays, Bash script, 91
  • assistive technology, 110, 115–116
  • at
  • atq, as root, 210
  • authentication
  • autofs, configuration files, default, 72

B

  • backups, 205
  • Bash, 54
    • bash function, 97
    • command history, 53
    • command substitution, 93
    • configuration files, locating on login, 88
    • environment settings, 47
    • executing commands, 87
    • file overwrite, preventing, 47
    • if conditionals, 88
    • initialization files, no reading, 91
    • logout, command execution, 87
    • output, redirect, 47
    • printing, list of numbers, 88
    • quotes, 57
    • reading commands, 87
    • sayHello function, 209
    • scripts, command-line parameters, 88
    • shell script, outputting name, 55
    • source built-in, 100
    • STDERR, redirecting, 52
    • STDOUT, redirecting, 52
    • umask setting, 79
  • Bash scripts
    • arrays, creating, 91
    • debugging, #! line, 96
    • division operator, 98
    • email, sending, 98
    • exit code, 95
    • find command, 96
    • functions, command sequence as, 89
    • greater than or equal to, 94
    • initialization, system wide, 94
    • keywords, 89, 95
    • loops, 100
    • output, 96
    • return values, testing, 95
    • terminating, 99
    • values, user entry, 96
    • variables, 95, 98, 208
  • Bash shell
    • invocation, file execution, 95
    • path, /srv/bin, 95
    • /user/local/lib, 28
    • /usr/local/bin, 100
  • .bash_history, 201
  • .bashrc, 201
  • BIOS (basic input/output system)
    • boot loader, disk location, 200
    • integrated peripherals, 20
  • blocks, reserving, 77
  • boot loaders, ISO9660 CD-ROMS, 14
  • boot order, 14
  • /boot partition
    • /dev/sdal, 33
    • extlinux, 33
  • booting
    • configuration, /etc/default/grub, 29
    • GUI, disabling, 105
    • initramfs, 14
    • No init found, 14
    • reboot, 7
    • troubleshooting, kernel ring buffer and, 7
  • bootstrapping, 205
  • Braille display, 107
  • btrfs subvolume, 75–76
  • built-in commands, listing read-only variables, 91
  • bunzip2, 61
  • bzip2, archive, sending to STDOUT, 56

C

  • case statement, 92–93
  • CentOS
    • groups, deleting, 217
    • packages, 37, 39
  • CentOS 6, RAM disk creation, 12
  • change, password changes, 191
  • character maps, 217
  • character sets, 125
  • characters
    • commands as function, Bash script, 89
    • multibyte representation, 126
    • sequence, alternate command, 89
  • child processes, variables, 208
  • chmod
    • execute permission, 97
    • minimum privileges, 90
  • chown, recursive change, 71
  • Chrony package, 152
  • chronyd, status, 156
  • CIDR (Classless Inter-Domain Routing), subnets
  • clock, hardware, 143
  • command-line
    • date, 143
    • parameters, Bash script, 88
  • commands. See also specific commands
    • aliased, removing, 90
    • executing two, 89
    • foreground processing, 50
    • history, 53
    • libraries, 29
    • locating elements, 69
    • paths, 61
    • return value test, 97
    • scheduling execution, 125
    • types, 57
  • compression, 59
    • decompressing files, 53
    • log files, disabling, 149
  • configuration
    • booting, 29
    • CUPS, 142
    • devices, udev, 6
    • /etc/hosts, 164
    • Ethernet devices, 173
    • files
      • autofs, 72
      • Bash, 86
      • Chrony, 152
      • locating on login, Bash, 88
      • logrotate, 156
      • modprobe, 196
      • priority order, 72
      • systemd, 8, 72
      • Upstart, 9
      • X clients, 107
      • XDMCP, 118
      • yum, 36
    • GRUB 2, 26, 201
    • IPv6, 166
    • kernel, 13
    • LightDM, 105, 111, 216
    • modprobe, 196
    • persistent, 157–174, 270–277
    • SSH custom client, 189
    • systemd, 13, 15
    • udev, 6
    • UEFI (Unified Extensible Firmware Interface), 15
    • Weston, 115
    • Wi-Fi devices, 173
    • X, 107, 112, 113
  • connectivity
    • testing, TCP level, 170
    • troubleshooting, 167
  • copying
    • directories, recursive, 49
    • files, at user creation, 90
  • copy-on-write, 73
  • cp, 202
    • confirmation, 100
    • directories, copying recursively, 49
    • file overwrite, 49
  • cpio, 56
  • CPU time, displaying, 180
  • cron, 124
  • crontab, 210
    • other users, 211
    • removing, 136
  • CUPS (Common UNIX Printing System)
    • configuration files, 142
    • daemon, listening on port 631, 150
    • default local printer configuration, 155
    • default port, 145
    • print jobs, completed, viewing, 146
    • print sharing, 149
    • restarting, 149
  • currency-related localization, 132
  • cut, delimiters, default, 50

D

  • data, writing to disk, 74
  • databases
    • hosts, enumerating, 163
    • updates, 71
  • date
    • command line, 143
    • current, 125
    • environment variables, 126
    • setting, 153
  • date, date/time set, 153
  • DATE variable, shell script, 92
  • dbus, communication, monitoring, 197
  • D-Bus, machine ID, 38
  • Debian
    • packages, 30–32, 33, 36, 38, 198–199
    • reconfiguration, 31
    • services, starting/stopping, 185
    • source repository, 198
    • startup scripts, 20
    • time zones, 133, 216
    • updates, 27
    • zsh package, 28
  • debugfs, 74
  • debugging
    • /etc/resolv.conf and, 172
    • messages, journalctl, 149
    • slapd, 132
    • XFS filesystem, 78
  • declare, 91, 93
  • decompressing files, 53, 60
  • default gateway, changing, 164
  • desktop, 113, 251–257
  • devices, 63–81
    • answers to review questions, 239–245
    • drivers, lsmod output, 11
    • empty, 78
    • filters, vgscan, 39
    • hotplug, udevadm commands, 6
    • input, acceleration, 107
    • NVMe-based, 18
    • USB, listing, 6
    • wireless, parameters, 168
  • /dev/sdal, /boot partition, 33
  • df, 79, 204
  • DHCP, activity, 171
  • dig, 162, 172, 173
  • directories
    • backups, user home, 37
    • changes, tilde character and environment variable, 92
    • copying recursively, 49
    • FHS, local binaries, 99
    • files, coping, 209
    • finding, 48
    • ldconfig, command-line, 38
    • printing, 54, 199
    • removing, 48
    • root user, home directory, 27
    • skeleton home directory, 136
    • system log, 155
    • time zones, 217
    • useradd, 128
    • users, changing, 130
  • display
    • accessibility, Orca, 112
    • assistive technology, 110
    • Braille, 107, 116
    • fonts, 107, 110
    • fonts.scale, 112
    • GDM (GNOME Display Manager), welcome message, 105
    • GNOME, 106, 108, 109, 114
    • GUI, boot disable, 105
    • inactivity timeout, 113
    • input devices, linear acceleration, 107
    • KDE, magnification, 108
    • LightDM, 105, 106, 110
    • monitor, 105, 106
    • mouse gestures, 108
    • RDP (Remote Desktop), server-side implementation, 114
    • screen magnifier, 116
    • video cards, RAM, 112
    • X
      • authority files, 108
      • local client, 111
      • monitor vertical refresh, 107
      • window information, 109
    • X Display Manager, login, 116
    • X session
      • information, 115
      • pointer keys, 114
      • terminal device width, 111
    • xauth authority file, 110
    • XFree86, hardware query, 106
    • xfwm4 window manager, 113
    • xorg.conf
      • blank mode, 109
      • video mode changes, 108
  • division operator, Bash script, 98
  • dmesg, time, 196
  • DNS (Domain Name System)
    • default route, 160
    • lookups, overriding, 166
    • POP3 server specification, 173
    • setting, 163
    • SPF query, 167
    • systemd-resolved, 173
  • documentation, access, 47
  • domain names, 162
  • DPMS (Display Power Management Signaling), 109, 113
  • drift file, location, 144
  • driftfile, 217
  • du, printing, 205
  • dumpe2fs, partition bad blocks, 73

E

  • e2fsck, superblocks, location, 79
  • egrep, 52
  • email. See also messages
    • abuse account, 146
    • aliases, 210
    • forwarding, Procmail, 150
    • per-user forwarding, 153
    • processing statistics, 149
    • removing, 150
    • root user, 144, 209
  • emulation, ping, 166
  • encrypted files, gpg, 187
  • encryption
    • passwords, 131
    • remote desktop, 113
  • env, 96
  • environment, Bash, 47
  • environment variables
    • date format, 126
    • declaring, 55
    • directory change, tilde character and, 92
    • localization, 127
    • paper size, 135
    • PS1, 87
    • removing, 87
    • removing temporarily, 57
    • single-line viewing, 99
    • terminal device, X session, 111
    • text editors, 58
    • time format, 126
    • usernames, 99
  • ESP (EFI system partition)
    • filesystem mount, 26
    • format type, 33
    • grub-install, 38
  • /etc/aliases, email messages, 150
  • /etc/default/grub, 29, 32
  • /etc/fstab, 72, 75, 81
  • /etc/hosts, 164, 171
  • /etc/hosts.allow, wildcards, 186
  • /etc/inetd.conf, services, disabling, 184
  • /etc/inittab, runlevel, single-user mode, 185
  • /etc/localtime, directory listings, 151
  • /etc/logrotate.conf, emailing log, 144
  • /etc/ntp.conf, drift file, location, 144
  • /etc/passwd, 49
  • /etc/resolv.conf, debugging and, 172
  • /etc/security/limits.conf, 182
  • /etc/shadow, 183, 188
  • /etc/sudoers, 214
    • admins group, 190
    • editing, 182
    • password prompt, 180
  • /etc/X11/xorg.conf, 105
  • /etc/yum.conf, kernel update, 32
  • Ethernet, device configuration, 173
  • event viewing, 6
  • Exam 1, practice exam, 284–288
  • Exam 101-500, practice exam, 288–292
  • executable files, location, 67
  • exFAT filesystem, formatting, 78
  • Exim server
    • mail delivery, 155
    • SMTP traffic and, 148
  • expiration, removing, 124
  • export
    • names as functions, 94
    • variables, 101
      • removing, 97
  • expressions, regular expressions, 59
  • ext2 filesystem, 68
    • journal, adding, 76
    • superblock, corrupt, 79
  • ext3 filesystem, 68
    • checking clean, 75
    • metadata image, 204
    • repairs, 204
  • extlinux, installation, /boot partition, 33

F

  • FAT (File Allocation Table)
    • formatting, 76
    • rescue disks, boot loader, 13
  • Fedora 22, packages, installation, 37
  • fgrep, 59
  • FHS (filesystem hierarchy standard), 69–70, 99
  • Fibre Channel, 17
  • file compression, 53, 59, 60
  • file dumps, maximum file size, 75
  • file tests, 95
    • operator, 98–100
  • $FILEPATH variable, 92
  • files
    • appending, 61
    • binary mode, 58
    • content search, 203
    • copying, 90, 209
    • decompressing, 53
    • existence, testing, 93
    • extracting, 50
    • group information, 126
    • gzip, 50
    • initialization, no reading, 91
    • line numbers, prepending, 53
    • listing, 56
    • moving, 54
    • open, listing, 186
    • overwriting, confirmation, 100
    • ownership, 68, 204
    • passwords, 125
    • removing, 55
    • removing lines, 60
    • searches, backward, 55
    • size, 55, 190
    • splitting, 60
    • tar, 50
    • UID, 125
    • usernames, 125
    • users, deleted, 79
  • filesystems
    • copy-on-write, 73
    • creating, bad blocks, 204
    • disk space, 70
    • ext2, 68
    • ext3, 68
    • extensions, missing, 49
    • hierarchy, 63–81, 239–245
    • information, 70
    • inodes, 68
    • ISO, creating, 72
    • Linux, 63–81
    • listing currently mounted, 34
    • mounted, 204
    • mounting, 69, 70, 71, 77
    • overwriting, 49
    • processes, running, 196
    • read-write mode, 74
    • ro, 73
    • sticky bits, 69
    • type, mke2fs, 72
    • unmounting, 74, 178
    • verifying, 74
    • xfs_check, 74
  • find, 54, 81, 97, 99, 205
  • firewalls
  • fonts, X.org, 107
  • fonts.scale, 112
  • for loops, 90, 93
  • foreground processing, 50, 51
  • fsck, 68, 72, 204

G

  • gateways, default, 160, 164
  • GDM (GNOME Display Manager)
    • greeter, welcome message, 105
    • login window options, 118
    • welcome message, 105
  • getent, password database, 136
  • GIDs, UIDs and, 130
  • GNOME
    • GOK (GNOME On-Screen Keyboard), 109
    • high-contrast theme, 108
    • on-screen keyboard, 119
    • screen reader, 106, 109
    • slow keys, 114
    • sticky keys, 106
  • GNU, commands, 41–61
    • answers to review questions, 233–239
  • GnuPG
    • key pair generation, 183
    • private keys, daemon process, 189
  • GOK (GNOME On-Screen Keyboard), 109, 111
  • gpg
    • detached signatures, 188
    • encrypted files, 187
    • keys, sending to key server, 190
    • public keys, 185
    • signatures, generating, 183
  • GPT disks
    • formatting, 77
    • partitions, Linux, 37
  • greater than or equal to operator, 94
  • grep, 100, 174
  • group ID, minimum group ID, 137
  • group information, 126, 127
  • group ownership of files, 68
  • groupadd, 135, 137
  • groupdel, 131
  • groups
  • GRUB
    • beep for input, 116
    • versus GRUB 2, 36
    • images, alternate directory, 34
    • MBR, SATA disk, 30
    • menu display, 25
    • operating system, default boot, 32
    • parameters, editing, 16
    • partitions, 25
    • ro option, 29
    • single-user mode, 25
    • timeout, setting, 28
  • GRUB Legacy
    • dual-boot option, 27
    • hd(0,0), 33
    • kernel options, 25
    • non-Linux kernel, 26
  • GRUB2
    • configuration changes, 201
    • configuration file, 26
    • versus GRUB, 36
  • grub-install, 34
    • boot images, 201
  • grub-mkconfig, 200
    • file output, 29
  • GUI (graphical user interface)
    • applications, screen, 209
    • boot disable, 105
  • .gz extension, 55
  • gzip files, 50

H

  • handshakes, three-way, 167
  • hardware, clock
  • head, 48, 51
  • /home/webfiles, 124
  • host, 160, 172
  • hostname
  • hostname, programmatic functions, 171
  • hosts
    • blocking, TCP wrappers and, 208
    • storing, ssh keys, 182
  • hosts database, enumerating, 163
  • hotplug devices, udevadm commands, 6
  • hwclock, system time, 145

I

  • IaaS (Infrastructure as a Service), performance, 36
  • ICMP (Internet Control Message Protocol)
    • echo requests, 216
    • packets, generating, interface, 161
    • ports, 164
    • requests for IPv6, 170
  • iconv, 125
  • if conditionals, Bash script, 88
  • ifconfig, MTU, network interfaces and, 168
  • ifup, 214
  • IMAPS (IMAP over SSL), listening port, 174
  • indexes, recreating, 130
  • init, process IDs, 196
  • initialization
    • files, no reading, 91
    • xinit, 117
  • initrd, filesystem, 16
  • inodes, 68
    • usage information, 81
  • input. See also assistive technology
    • devices, acceleration, 107
  • installation
    • Fedora 22 system, 37
    • Linux, 21–39, 226–232
    • rpm, 28
    • yum package, 27
    • zypper, 37
  • interfaces, 105–119
    • answers to review questions, 251–257
    • auto, online, 161
    • displaying information, 160
    • selecting, 161
  • interprocess communication service units, systemd, 188
  • ip, 168, 174, 215
  • IP addresses, availability, 167
  • ip route change, 166
  • iproute2, address changes, 173
  • IPv4/ IPv6 comparison, 164
  • IPv6
    • addresses, 161, 170
    • configuration, 166
    • IPv4comparison, 164
    • pings, unique local address, 165
    • route traces, 172
    • traceroute, 162
  • IRQ (interrupt request), assignments, viewing, 6
  • ISO filesystem, creating, 72
  • ISO9660 CD-ROMS, boot loader, 14

J

  • JAVA_PATH, 201
  • job schedulers, 125, 126, 127, 128, 133, 136
  • jobs, 56, 61
  • journal logs, files, maximum size, 147
  • journalctl, 149
    • filters, time-based, 154
    • journal data location, 155
    • journal data size, 153
    • kernel message queries, 152
    • logs, clearing, 150
    • maximum space, 154
    • new log entries, 147
    • service names, 153
  • journald.conf, file size, 147

K

  • KDE
    • magnification, 108
    • speech recognition, 114
  • keepalive messages, 190
  • kernel
    • configuration information, 13
    • messages, 142, 152
    • modules, listing, 8
    • printing information, 47
    • ring buffer, 7, 9
    • symbols, files, 12
    • udev events, 6
    • updating, 32
  • key pairs, 179, 183
  • keyboard, 209
  • keys, listing current, 181
  • keywords, Bash scripts, 89, 95
  • kill, 20, 51, 52, 57
  • killing processes, 54
  • klogd, logging messages, 145

L

  • LANG variable, 128
  • last, recent login details, 184
  • LDAP (Lightweight Directory Access Protocol), 213
    • entries, importing, 124
    • LDIF file, creating, 127
    • local files, lookups, 162
    • over SSL, listening, 133
    • user list, 127
  • LDAP over SSL, port, 166
  • ldconfig
    • cache location, 198
    • directories, 35, 38
    • library path, directories, 35
  • LDIF files, creating, 127
  • libraries
    • availability, 81
    • commands, 29
    • printing, 199
    • shared, 26
    • storage, 30
  • libwrap, 191
  • LightDM
  • lightdm.conf, SeatDefaults section, 117
  • line numbering, 201
  • linear acceleration, input devices, 107
  • link status, displaying, 168
  • links, symbolic, 79
  • Linux
    • / filesystem, 200
    • /boot partition, size, 30
    • directory structure, 27
    • documentation, access, 47
    • filesystems, 63–81, 239–245
    • GIDs, versus UIDs, 130
    • initialization, single-user mode, 7
    • installation, 21–39, 226–232
    • package management, 21–39, 226–232
    • partition, non-swap, 67
    • partition structure, 27
    • swap, 30
    • swap space, deactivating, 76
    • system logs, 155
    • time zones, 124, 143
    • UIDs, versus GIDs, 130
  • ln, symlinks, 69
  • load average
    • determining, 51
    • uptime, 203
  • loading, modules, 6
  • locale
    • currency-related, 132
    • LANG variable, 128
    • reconfiguring variables, 128
  • locale, 134
  • localhost, redirecting to, 166
  • locate, 71, 80
  • log files
    • compression, disabling, 149
    • entries, parsing, 211
    • journal logs, maximum size, 147
    • journalctl, 150
    • rotation, configuring, 148
    • systemd, disk space used, 144
  • log in
    • automatic, LightDM, 111
    • message display, 18, 19
    • number logged, 191
    • number of, 182
    • password-based, 128
    • preventing temporarily, 178
    • users logged in, 180
    • X Display Manager, 116
  • log zeroing, 77
  • logging
    • kernel messages, 142
    • messages, klogd, 145
  • logical volumes, 18
  • login name, changing, 189
  • logout, command execution, Bash shell, 87
  • logrotate, 142, 149, 156, 212
  • logs, emailing, /etc/logrotate.conf, 144
  • lookups, 162
  • loops, 90, 100, 101
  • ls, 48, 87
  • ls -la, output, 67
  • lsblk
    • empty devices, 78
    • filesysem UUID, 80
    • partitions, 200
  • lsof, instances, open, 215
  • lspci, 8, 12
  • LUN (logical unit number), 17
  • lvchange, logical volume availability, 35
  • LVM (Logical Volume Manager), 30, 31, 32, 34, 35
  • .lzma extension, 53

M

  • MAC (Media Access Control), 168
  • mail, 153, 155
  • mail servers, querying for, 161
  • man, 52
  • man pages, 56, 59
  • MBR partitioning system, 26, 30
  • MBR-formatted disks, partition size, 77
  • measurement, environment variables, 127
  • /media/ mount point, 78
  • memory
  • menu.lst, 29
  • messages. See also email
    • all users, 8
    • debugging, journalctl, 149
    • keepalive, 190
    • log, klogd, 145
    • Postfix server, 146, 150
    • subject, 153
  • MIME types, 134
  • minimum group ID, 137
  • mke2fs, 72, 204
  • mkfs.ext4, block reservation, 77
  • mkswap, back block check, 80
  • modprobe
    • configuration information, 196
    • module dependencies, 8
    • modules, blacklist information, 12
  • monitors, 105, 106
  • mount, 69, 73
  • mount points, 38
    • FHS, removable media, 70
    • maximum, 73
    • /media/, 78
  • mounting
    • filesystems, 69, 70, 71, 77
    • partitions and, 67, 76
    • simulating mount process, 73
    • unmounting, 74, 178
    • USB disk, 67
  • mouse gestures, 108
  • moving, files, 54
  • MTU, network interfaces, 168
  • mv, file overwrite, 49

N

  • nagios, monitoring, 50
  • name resolution, 168, 186, 213
  • netcat, servers, listening ports, 165
  • netlink, messages, listening for, 162
  • netmasks, subnets, CIDR notation, 163
  • netstat
    • -a, 216
    • process ID, 179
    • sockets, send and receive queues, 163
  • Network Manager, 166, 172, 173
  • networks, persistent configuration, 157–174, 270–277
  • nl, 201
  • nmap
    • name resolution, 186
    • open ports, finding, 184
    • UDP and, 215
  • nptd, synchronization, time and, 147
  • NTP (Network Time Protocol)
    • interactive mode, 144
    • internally facing, 168
    • ntpdate, 211
    • time, 142
  • ntpdate, 211
  • ntpq, messages, 143
  • numbering lines, 201
  • NVMe-based devices, 18
  • NXDOMAIN, 173

O

  • OnCalendar systemd, 136
  • OpenLDAP
    • corrupted, recovery, 131
    • database storage, 137
    • entries, adding, 129
    • slapd, 126
  • operators, 94, 98, 99, 100
  • Orca, 112, 116, 216
  • out-of-memory conditions, 50
  • output, realtime viewing, 56
  • overwriting files, 49, 100
  • ownership of files, group ownership, 68

P

  • packages
    • cache update, Debian systems, 30
    • CentOS, 37, 39
    • Debian, 28, 31, 32, 33, 36
    • information, Debian, 199
    • installation, Fedora 22 system, 37
    • Linux, 21–39
    • RPM, downloading, 28
    • upgrades, yum, 199
    • upgrading, rpm, 199
    • yum, 27, 28, 31
    • zypper, installation, 37
  • packet forwarding, number of packets, 168
  • packets, statistics, 213
  • pagers, backward/forward search, 58
  • parameters, wireless devices, 168
  • partitions
    • bad blocks, 73
    • GRUB, 26
    • images, 49
    • initial sector, 33
    • Linux systems, 27, 67
    • lsblk, 200
    • LVM (Logical Volume Manager), initializing, 30
    • mail servers, 26
    • MBR system, 26, 77
    • mounting and, 67
    • swap partitions, formatting, 70
    • type 0x82, 67
    • UUID, 74
  • passwd, 187, 214
  • passwordfile, /etc/passwd, 49
  • passwords
  • paths, 61
    • ~/code/bin, 208
    • removing from results, 69
  • PCI devices, 196
  • permissions
    • chmod, 90
    • editing, simultaneous, 79
    • execute, 97
    • granting, 78
    • ls command, 88
    • root privileges, 189
    • setgid, 80
  • persistent configuration, 157–174, 270–277
  • pgrep, 57
  • ping, 161, 166, 213
  • pkill, 61
  • plaintext files, octal representation, 202
  • pointer keys, X session, 114
  • POP3, DNS and, 173
  • port scans, TCP connect, 187
  • port-forwarding, local session, 183
  • ports
  • port-to-protocol translation, 163
  • POSIX (Portable Operating System Interface), umask and, 68
  • Postfix server
  • power, shutdown, 19
  • practice exams
    • Exam 1, 284–288
    • Exam 101-500, 288–292
  • prepending line numbers, 53
  • printing
    • adding jobs to queue, 153
    • deleting jobs, 212
    • directories, 54, 199
    • head, default number printed, 48
    • human-readable format, 205
    • libraries, 199
    • lpr option, 154
    • queue, placing file, 145
    • removing jobs, 152, 155
    • tail, default number printed, 48
    • users, groups, 148
    • viewing jobs, 147
    • wc, number of lines, 47
  • private addresses, internal use, 160
  • /proc filesystem, 11
  • process IDs, 50, 196, 203
  • processes
    • child, variables, 208
    • killing, 54
    • priorities, 52
    • reprioritizing running, 59
    • running, 196
  • Procmail, email forwarding, 150
  • programs, crashing, 50
  • protocols
  • ps, aliases, 208
  • PS1 environment variable, 87
  • ps-based commands, 57
  • public/private key pair, ssh, 179

R

  • RAID (Redundant Array of Inexpensive Disks), 17
  • RAM, video cards, 112
  • rc files, runlevels, 13
  • RDP (Remote Desktop), 114, 119
  • read access, granting, 78
  • README file, missing, 96
  • readonly, 99
  • read-only mode, filesystem mounting, 77
  • read-only variables, 91, 93
  • read-write mode, 74
  • reboot, commands, 7
  • recursive copy, symlinks, 202
  • Red Hat, 15, 217
  • regular expressions, 59
  • remote desktop, 113, 115
  • remote forwarding, SSH, 191
  • remote hosts, port setting, 183
  • remote servers, command execution, 181
  • remote system logging, 156
  • removable media, mount points, FHS, 70
  • repositories, yum, 29
  • rm, 55
  • rmdir, 48
  • rmmod, module, unloading, 11
  • ro, GRUB file, 29
  • root user, home directory, 27
  • route, 167, 168, 171
  • rpm, 28, 29, 31, 38, 199
  • RPM, packages, downloading, 28
  • rpm2cpio, output location, 27
  • RSA-based key pairs, 181, 184
  • rsyslogd, server listening, 147
  • runlevel
    • default, 16
    • display, 7
  • runlevels, systemctl, 16
  • running tasks, backgrounded, 53

S

  • SAN (storage area network), 11
  • SATA (Serial Advanced Technology Attachment)
    • disks, 197
    • identifiers, 25
  • sayHello function, 209
  • scheduling
    • certain time, 133
    • command execution, 125
    • cron, 126
    • directories, 136
    • listing jobs, 133
    • power down and, 125
    • scheduled jobs, finding, 127
    • script directory, 128
  • screen magnifier, 116
  • screen resolution, 106
  • scripts. See also Bash scripts
    • answers to review questions, 245–251
    • changes, 68
    • command line, date, 143
    • domain names, server, 162
    • execute then leave, 89
  • SCSI (Small Computer System Interface), 18
  • searches, 55, 58, 60
  • Secure Shell, ports, 164
  • security, 175–192, 277–284
  • sed, 47
  • sendmail, 145, 146, 148, 149
  • seq, delimiters, 95
  • server host keys, SSH, 189
  • servers
    • routes, adding, 163
    • setgid bit, 185
  • set, 94
  • setgid, file permissions, 80
  • setuid bit set, 178
  • shared libraries, 26
  • shebang line, 97
  • shell scripts, 85–101
    • answers to review questions, 245–251
    • DATE variable, 92
    • files, existence, 90
    • permission denied, 94
    • shebang line, 97
    • syslog, logging to, 152
    • variable contents, displaying, 88
    • variables, user input, 89
  • shells, 85–101
    • answers to review questions, 245–251
    • built-in commands, 71, 91
    • script, execute then leave, 89
  • shutdown, 10, 19, 198
  • shutdown command, 19
  • SIGHUP signals, 56
  • SIGKILL, 20
  • single-user mode, 14
  • skeleton home directory, 136
  • slapadd, line number specification, 134
  • slapd, 126, 130, 132
  • SMART (Self-Monitoring, Analysis, and Reporting Technology), compatible hard drives, 74
  • SMTP (Simple Mail Transfer Protocol), 148, 151
  • snapshots, btrfs subvolumes, 76
  • SNMP (Simple Network Management Protocol), ports, 162
  • SOA (Start of Authority), 213
  • source built-in, 100
  • speech capabilities, Orca, 216
  • speech recognition, KDE, 114
  • SPF (Sender Policy Framework), 167
  • Spice, authentication disable, 113
  • .sql extension, searching for, 80
  • srv/vhosts, 35
  • ss, process IDs, 171
  • SSD (solid-state drive), hardware, NVMe (Non-Volatile Memory Express), 17
  • ssh
    • authentication key, enabling, 184
    • key-based authentication, 179, 184
    • public/private key pair, 179
    • remote host port, 183
    • username change, 213
    • X11 application forwarding, 187
  • SSH (Secure Shell)
    • custom client configuration, 189
    • hosts, 182
    • keys, adding, 187
    • keys, virtual machine cloud deployment, 37
    • new windows, X forwarding and, 105
    • remote forwarding, 191
    • server host keys, 189
    • server-wide client, 191
    • sudoers, 114
    • visudo, 114
    • X sessions, 110
  • ssh-agent, keys, listing current, 181
  • ssh-keygen, 188, 191
  • Start of Authority, information display, 165
  • STDERR, redirect, 52
  • STDIN, mail, 217
  • STDOUT, redirect, 52
  • sticky bits, 69
  • sticky keys, GNOME, 106
  • storage, libraries, 30
  • su, 181, 186
  • subnets, 215
  • sudo, 53, 78, 184, 214
  • sudoers, SSH connection, 114
  • suehring, 179
  • swap partitions, formatting, 70
  • swap space (Linux), 30
    • activating, 34
    • deactivating, 76
    • determining, 50
    • swapon, 39
  • swapon, 39
  • switch statement, 92
  • symbolic links, 79
    • file test operators, 99
    • find, 205
  • symlinks
    • ln, 69
    • recursive copy, 202
  • sysfs filesystem, MAC addresses, 197
  • syslog
    • - sign in configuration, 154
    • custom log files, 148
    • informational messages, 143
    • logging to, 152
    • lp printing, 217
  • syslog-ng, configuration files, primary, 148
  • system architecture, 3–20, 220–226
  • system clock, 134
  • system logs, Linux directories, 155
  • system services, 139–156
    • access allowed, 188
    • answers to review questions, 263–270
    • libwrap, 191
    • listening, 186
    • loaded, 9
    • preventing startup, 181, 182
  • system time, 145, 146
  • systemctl, 11
    • processes, killing, 197
    • runlevels, 16
  • systemctl kill, 198
  • systemd, 198
    • active timer display, 136
    • boot messages, 19
    • booting, 17
    • configuration files, 8, 72
    • configurations, 13
    • default target, 10
    • GUI, boot disable, 105
    • interprocess communication service units, 188
    • journal, 142, 149, 172, 212
    • location specification, 76
    • log file, 142, 144
    • logging, 142
    • multi-users, 16
    • network interface management, 174
    • output logging, 152
    • overriding configuration files, 15
    • program executing, 10
    • service units, listing, 8
    • single-user mode command, 9
    • storage, 13
    • timer units, 134, 135
    • udev, 197
    • user init files, 14
  • systemd-resolved, DNS resolution, 173
  • systemd-run, timed events, 132
  • systemed, timer units, 138
  • SysV system
    • chkconfig, services, 9
    • init, 7, 15
    • process termination, 19
    • scripts, starting/stopping, 15
  • SysVinitu environment, 198

T

  • tail, 48, 51, 202
  • tar files, 50
  • tasks
    • administrative, 124–138
    • running, backgrounded, 53
  • TCP (Transmission Control Protocol)
    • remote system logging, 156
    • wrappers, blocking hosts, 208
  • tcpdump, available interfaces, 170
  • tee, appending, 205
  • telinit, 197
  • terminal processing, 51, 56
  • terminal-based interface, package management, Debian, 31
  • test built-in command, arguments, not null, 92
  • text, formatting, 202
  • TFTP (Trivial File Transfer Protocol), PXELINUX, 15
  • three-way handshake, 167
  • time
    • current, 125
    • dmesg, 196
    • environment variables, 126
    • hardware clock, 143
    • NTP (Network Time Protocol), 142
    • setting, 153
    • system clock, 134, 145, 146
    • system time, offline devices, 145
  • timedatectl, 134, 151
  • timezones
  • top, 60, 203
  • touch, 48
  • tracepath, 165
  • traceroute, 165
    • ICMP, request and, 171
    • IPv6 route traces, 172
    • TCP SYN packets, 161
  • traceroute, !H, 215
  • traceroute6, IPv6 traceroute, 162
  • traffic, route limiting, 165
  • transport layer security, remote desktop, 115
  • tune2fs, 73, 75, 77
  • type 0x82 partition, 67

U

  • Ubuntu
    • accessibility, 209
    • images, deploying to remote provider, 36
  • udev, 6, 12
  • udevadm commands, hotplug devices, 6
  • UDP, nmap, 215
  • UEFI (Unified Extensible Firmware Interface)
    • boot configuration, 15
    • boot loaders, 14
    • booting, shim, 16
  • UG flags, 167
  • UIDs
  • ulimit, memory limits, 187
  • umask, POSIX format and, 68
  • umount, 71, 178
  • uniq, 202
  • UNIX, commands, 41–61, 233–239
  • unset, 87
  • unset option, 97
  • updates, kernels, 32
  • Upstart, configuration files, 9
  • uptime, load average information, 203
  • USB (Universal Serial Bus)
    • connections, information, 11
    • devices, 6, 9, 10
    • disks, mounting, 67
    • drives, 10
    • temporary disk, removing, 10
  • user information, 137
  • useradd
    • account disabled, 210
    • adding groups, 130
    • home directory, 128
    • password expiration, 210
  • usermod, 131, 189
  • usernames
    • changing, 189, 213
    • environment variables, 99
    • files, 125
    • printing, 202
    • sorted list, 48
  • users
    • account expiring, 182
    • deleting, 79, 125, 211
    • directories, 130, 133
    • executing commands on, 180
    • expiring account, 180
    • file copying, 90
    • interfaces, 105–119, 251–257
    • limits, 180, 181, 191
    • logged in currently, 180
    • login, preventing temporarily, 178
    • messaging all, 8
    • names, printing, 202
    • printing, from password file, 188
    • time zones, 127
    • useradd, 128
  • /usr/local, directories, creating, 49
  • UTC (Coordinated Universal Time)
    • hardware clock, current system time, 146
    • output to, 212
  • UUID
    • lsblk and, 80
    • partition identification, 72, 74

V

  • variables
    • Bash script, 98, 208
    • child processes, 208
    • DATE, 92
    • environment
      • declaring, 55
      • localization, 127
      • paper size, 135
      • PS1, 87
      • removing, 87
      • single-line viewing, 99
      • terminal device, X session, 111
      • usernames, 99
    • export, 101
    • exported, 101
    • $FILEPATH, 92
    • read-only, declare, 93
  • .variables.sh, 208
  • vgscan, devices, filters, 39
  • Vi editor
    • cursor, moving, 58
    • files, removing lines, 60
    • insert mode, 52
    • moving to line, 203
    • save and exit, 51
    • searches, backward, 55
  • video cards, RAM, 112
  • virtual machine
    • boot process, 25
    • bootstrapping, 205
    • deployment, 36
  • virtualization, 35, 39
  • visudo, SSH connection, 114
  • volumes, logical volumes, 18

W

  • wall, user log off, 196
  • Wayland protocol, 113
  • wc, printing, number of lines, 47
  • web server, /home/webfiles, 124
  • Weston, configuration, 115
  • while loops, 90, 91, 93, 101
  • Wi-Fi, device configuration, 173
  • wildcards, 60
    • /etc/hosts.allow, 186
  • wireless devices, parameters, 168
  • wireless networks, scanning for, 168
  • WWN (World Wide Name), directory hierarchies, 18

X

  • X
    • abbreviations, 112
    • authority files, 108, 115
    • clients, executing, configuration file, 107
    • configuration
      • keyboard model, 107
      • Screen section, 112
      • server layouts, 112
    • local client, display, 111
    • SSH (Secure Shell), 110
    • window information, 109
  • X Display Manager, login, 116
  • X forwarding, SSH server, new windows, 105
  • X server
    • clean exit, 108
    • configuration, 107, 113
    • connections, closing, 117
    • defaults, restoring, 117
    • error log, 117
    • hosts, 110, 116
    • init, 117
    • resources, freeing, 117
    • TCP, listening disable, 116
    • user access, 210
  • X session, pointer keys, 114
  • X windows, 216
  • X11, 118, 187
  • x11vnc, passwords, 114
  • xauth, 117, 119
  • xauth authority file, 110
  • xauth utility, X authority files, 108
  • XDMCP
    • BroadcastQuery packets, 118
    • configuration file, 118
    • host access, 108
  • XFree86, hardware query, 106
  • XFS filesystem, 73, 78
  • xfs_check, 74
  • xfs_fsr, filesystem reorganization time, 78
  • xfs_metadump, progress indicator, 70
  • xfs_repair, log zeroing, 77
  • xfsrestore, options, 75
  • xfwm4 window manager, 113
  • xhost, hosts, enabling, 118
  • xinit, per-user initialization, 117
  • X.org, font storage, 107
  • xorg.conf
    • blank mode, 109
    • Files section, fonts, 110
    • inactivity timeout, 113
    • Module section, 106
    • video mode changes, 108
  • Xsession, 111, 115, 118
  • xzcat program, 58

Y

  • yum
    • configuration file, primary, 36
    • package cache search, 31
    • package installation, 27
    • packages, 28, 199
    • repositories, 29
    • verification prompt, 199
  • yumdownloader, dependencies, downloading, 32

Z

  • zone transfer, 167
  • zsh, searching for, 28
  • zypper, packages, installation, 37
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