System Architecture (101)
13.3%of exam
Installation & Packages (102)
20%of exam
GNU & Unix Commands (103)
43.3%of exam
Devices & Filesystems (104)
23.3%of exam
Quick Facts
- Exam
- 101-500
- Credential
- LPIC-1 (Part 1 of 2)
- Time
- 90 min
- Pass
- 500 of 800
- Level
- Junior admin
- Format
- MC + fill-in-blank
- Blueprint
- v5.0 (Oct 2018)
Runlevel Map
0=off 1=rescue 2-4=multi 5=GUI 6=reboot
0: poweroff.target1: rescue.target2-4: multi-user.target5: graphical.target6: reboot.target
dmesg vs journalctl -b
dmesg
- Kernel messages only
- Lost at reboot
journalctl -b
- Kernel plus service messages
- Persistent if storage configured
Kernel buffer vs system journal
Boot & Target Picker
- Switch target right now→systemctl isolate(No reboot needed)
- Change target for future boots→systemctl set-default(Takes effect next boot)
- Check the current default→systemctl get-default(Read-only, no change)
- Need single-user maintenance mode→rescue.target(Runlevel 1)
- Need graphical login screen→graphical.target(Runlevel 5)
- Need multi-user, no GUI→multi-user.target(Runlevel 2, 3, or 4)
- See log for current boot→journalctl -b(Current boot; -b -1 previous)
- See kernel-only ring buffer→dmesg(Lost at every reboot)
Hardware Discovery
- lspci
- Lists PCI bus devices
- lsusb
- Lists USB devices
- lsmod
- Lists loaded kernel modules
- modprobe
- Loads or removes a module
- /proc
- Kernel and process info
- /sys
- Kernel objects, tied to udev
- udevadm
- Queries device manager events
- lscpu
- Shows CPU architecture details
Boot Sequence
- BIOS/UEFI
- Firmware initializes hardware first
- Bootloader
- Loads kernel and initramfs
- initramfs
- Temporary early-boot root filesystem
- init/systemd
- First process, PID 1
- journalctl -b
- Shows current boot's journal
- journalctl -b -1
- Shows previous boot (persistent only)
- dmesg
- Kernel ring buffer only
Runlevels & Targets
- Runlevel 0
- poweroff.target
- Runlevel 1
- rescue.target, single-user mode
- Runlevel 2-4
- multi-user.target, no GUI
- Runlevel 5
- graphical.target
- Runlevel 6
- reboot.target
- systemctl isolate
- Switch target now
- systemctl set-default
- Change future boot target
- systemctl get-default
- Show current default target
- telinit
- Legacy SysVinit runlevel switch
RPM Query Flags
-qa all, -qf owner, -qi info, -ql files
-qa: every installed package-qf: file's owning package-qi: package info summary-ql: package's file list
dpkg vs apt
dpkg -i
- Installs local .deb file
- No dependency resolution
apt install
- Resolves dependencies
- Downloads from repositories
Low-level vs high-level tool
Package Manager Picker
- Debian/Ubuntu install package→apt install(Resolves deps)
- Debian/Ubuntu find file owner→dpkg -S(Maps file to package)
- Have a local .deb file→dpkg -i(No dependency resolution)
- RHEL/Fedora install package→dnf install(Resolves deps)
- Older RHEL/CentOS system→yum install(Resolves deps)
- SUSE install package→zypper install(Resolves deps)
- Have a local .rpm file→rpm -Uvh(No dependency resolution)
- Find file's owning package→rpm -qf(RPM systems only)
Disk Layout & Boot
- /boot
- Holds kernel and initramfs
- ESP
- UEFI boot partition, FAT
- swap
- Extends RAM, stores hibernation image
- LVM
- Logical volumes across disks
- grub-install
- Writes boot code once
- grub-mkconfig
- Regenerates grub.cfg boot menu
- update-grub
- Debian wrapper for grub-mkconfig
- /etc/default/grub
- Source file grub-mkconfig reads
grub-install vs grub-mkconfig
grub-install
- Writes boot code
- Run once per disk
grub-mkconfig
- Regenerates grub.cfg
- Run after config changes
Install vs configure
Debian Packages
- dpkg -i
- Installs a local .deb file
- dpkg -L
- Lists files owned by package
- dpkg -S
- Finds package owning a file
- dpkg -l
- Lists all installed packages
- apt-get install
- Resolves and installs dependencies
- apt-cache search
- Searches downloaded package metadata
- apt-cache show
- Shows package details, no install
- /etc/apt/sources.list
- Debian repository source list
RPM Packages
- rpm -qa
- Lists every installed package
- rpm -qf
- Finds package owning a file
- rpm -qi
- Shows installed package info
- rpm -Uvh
- Installs or upgrades local RPM
- dnf install
- Resolves deps on Fedora/RHEL
- yum install
- Resolves deps on older RHEL
- zypper install
- Resolves deps on SUSE
- /etc/yum.repos.d/
- RPM repository config directory
Virtualization Guest
- cloud-init
- Sets hostname, keys, users on boot
- dmidecode
- Reads hypervisor SMBIOS/DMI data
- VM guest
- Runs under a hypervisor
- Container
- Shares the host kernel
Quoting Strength
Single blocks all, double still expands
Single quotes: fully literalDouble quotes: expands $varsBackslash: escapes one character
cp -r vs cp -a
cp -r
- Recursive copy
- New ownership
- Current timestamp
- umask permissions
cp -a
- Archive mode
- Preserves ownership
- Preserves timestamps
- Preserves links/xattrs
Recursive vs archive copy
Shell Basics
- Single quotes
- No expansion at all
- Double quotes
- Expands $var and $(cmd)
- export VAR=value
- Child processes inherit it
- VAR=value
- Shell-only, not inherited
- type
- Checks alias, builtin, function, file
- which
- Searches $PATH executables only
- history
- Lists past shell commands
- alias
- Names a shortcut command
Grep Family
egrep is grep -E; fgrep is grep -F
-E: extended regular expressions-F: fixed literal string matchegrep = deprecated grep -Efgrep = deprecated grep -F
rm -r vs rm -rf
rm -r
- Recursive delete
- Prompts on protected files
rm -rf
- Recursive delete
- Never prompts, ignores errors
Interactive vs forced delete
Text Filters
- cut -f
- Extracts delimited fields
- cut -c
- Extracts character positions
- sort -u
- Sorts and removes duplicates
- uniq
- Removes adjacent duplicates only
- sed (no g flag)
- Replaces first match per line
- sed (g flag)
- Replaces every match per line
- tr
- Translates or deletes characters
- wc -l
- Counts lines in input
sort -u vs uniq
sort -u
- Sorts input first
- Removes all duplicates
uniq
- Needs pre-sorted input
- Removes adjacent duplicates only
Global vs adjacent dedupe
File Management
- cp -r
- Recursive copy, new metadata
- cp -a
- Archive copy, preserves all
- rm -r
- Recursive delete, prompts sometimes
- rm -rf
- Recursive delete, never prompts
- find -name
- Quote the pattern always
- tar -czf
- Creates a gzip archive
- tar -xzf
- Extracts a gzip archive
- dd
- Copies data block by block
Streams & Redirects
- Overwrite (>)
- Truncates then writes output
- Append (>>)
- Appends output, keeps existing
- Redirect stderr (2>&1)
- Stderr follows stdout's target
- Redirect both (&>)
- Sends stdout and stderr together
- Pipe (|)
- Sends output to next command
- tee
- Writes to file and stdout
- xargs
- Builds arguments from stdin lines
Process Control
- ps aux
- BSD style, shows %CPU/%MEM
- ps -ef
- UNIX style, always shows PPID
- kill
- Sends SIGTERM (15) by default
- kill -9
- Sends SIGKILL, cannot be caught
- nice
- Sets niceness at launch, +10
- renice
- Changes priority of a running PID
- nohup
- Ignores SIGHUP, doesn't background it
- jobs / fg / bg
- Lists, foregrounds, backgrounds jobs
Regex & grep
- Anchor (^)
- Matches start of line
- Anchor ($)
- Matches end of line
- grep -E
- Extended regex, same as egrep
- grep -F
- Fixed string, same as fgrep
- grep -i
- Case-insensitive pattern matching
- grep -v
- Inverts the match, excludes lines
- Class ([^abc])
- Matches any char not listed
- regex(7)
- Linux manual page for regex
vi Editor
- Normal mode
- Default mode for navigation
- Insert mode
- Enter with i, a, or o
- Command-line mode
- Enter with : for ex commands
- dd
- Deletes (cuts) the current line
- yy
- Yanks (copies) the current line
- p
- Pastes buffer after cursor line
- :wq
- Saves changes, then quits
- ZZ
- Saves if changed, then quits
- :q!
- Quits, discarding unsaved changes
umask Bit Math
022 masks bits: files 644, dirs 755
File base is 666Dir base is 777022 gives 644 and 755
MBR vs GPT
MBR
- 4 primary partitions max
- 2 TiB address limit
GPT
- 128 partitions by default
- UEFI-standard partition scheme
Legacy vs modern partition table
Filesystem/Mount Picker
- Need UUID for fstab entry→blkid(Prints type, UUID, label)
- See device and partition tree→lsblk -f(Adds type, label, UUID)
- Filesystem stuck read-only→mount -o remount,rw(No unmount required)
- Check an ext4 filesystem→e2fsck(Unmount first, or read-only)
- Need to shrink a filesystem→ext4 + resize2fs(XFS cannot shrink at all)
- Need to grow XFS online→xfs_growfs(Grow only, no shrink)
- Copy directory, keep everything→cp -a(Owner, time, links preserved)
- Delete with zero prompts→rm -rf(Silent on missing files)
Partitioning
- MBR
- 4 primary partitions, 2TiB limit
- GPT
- 128 partitions default, UEFI standard
- fdisk
- Classic MBR/GPT partition tool
- parted
- Script-friendly partitioning tool
- mkfs.ext4
- Formats an ext4 filesystem
- mkfs.xfs
- Formats an XFS filesystem
- mkswap
- Formats a swap partition
hard link vs symbolic link
Hard link (ln)
- Shares the original inode
- Cannot cross filesystems
Symlink (ln -s)
- Separate inode holding a path
- Can cross filesystems
Same inode vs path pointer
Filesystem Integrity
- e2fsck
- Repairs ext filesystems, unmounted
- du
- Sums allocated disk blocks
- df
- Reads free space from superblock
- tune2fs
- Tunes ext filesystem parameters
- XFS resize
- Can only grow, never shrink
- ext4 resize
- Can grow or shrink (resize2fs)
Mounting
- /etc/fstab
- Device, mount point, type, options
- mount -o remount,rw
- Switches to read-write, no unmount
- blkid
- Shows type, UUID, and label
- lsblk -f
- Shows device tree plus UUID
- UUID
- Stable id, use it in fstab
Permissions & Links
- umask 022
- Files get 644, dirs 755
- setuid
- Runs as the file owner
- setgid
- New files inherit dir group
- sticky bit
- File/dir owner or root deletes
- ln
- Hard link, shares an inode
- ln -s
- Symlink, can cross filesystems
- chmod 4755
- Sets setuid plus rwxr-xr-x
FHS Layout
- /etc
- Static host configuration files
- /var
- Variable runtime data, logs
- /usr
- Installed programs, shared data
- /opt
- Optional third-party applications
- /tmp
- Temporary files, cleared often
- find
- Searches the live filesystem
- locate
- Queries a prebuilt index
Common Traps
Runlevel numbers
Runlevels 2, 3, 4 = multi-user ≠ Only 0, 1, 5, 6 differ
Copy recursive vs archive
cp -r resets ownership/time ≠ cp -a preserves everything
which vs type
which checks $PATH only ≠ type also finds builtins
kill default vs kill -9
Default sends SIGTERM (15) ≠ -9 sends SIGKILL, uncatchable
XFS vs ext4 shrink
XFS can only grow ≠ ext4 can grow or shrink
Single vs double quotes
Single blocks all expansion ≠ Double still expands $vars
MBR primary partition limit
4 primary partitions max ≠ 3 primary plus 1 extended
Last Minute
- 1.60 questions in 90 minutes
- 2.Pass score is 500 of 800
- 3.60 weight points, one per question
- 4.103 GNU/Unix commands is largest
- 5.Runlevels 2, 3, 4 = multi-user
- 6.cp -a preserves owner, time, links
- 7.umask 022 gives files 644
- 8.umask 022 gives dirs 755
- 9.kill -9 cannot be caught
- 10.XFS filesystems can only grow
- 11.Run grub-mkconfig after editing GRUB
- 12.Fix broken deps: apt --fix-broken install
- 13.Retake wait: 7 then 14 days
- 14.2-year lock after passing exam
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