brainscape_system_admin_flashcards

Question 1

Front

Answer 1

Back

Question 2

Linux

Answer 2

Open‑source OS kernel used by many distributions.

Question 3

Distribution (distro)

Answer 3

Packaged Linux + tools; examples: Ubuntu, Debian, Fedora, Arch.

Question 4

Kernel

Answer 4

Core that manages CPU, memory, devices, and system calls.

Question 5

GNU userland

Answer 5

CLI tools (coreutils, bash, grep, sed, awk) that sit above the kernel.

Question 6

Shell

Answer 6

Command interpreter; common: bash, zsh, fish.

Question 7

Terminal

Answer 7

Program that emulates a TTY to interact with the shell.

Question 8

Absolute path

Answer 8

Path from root / (e.g., /etc/hosts).

Question 9

Relative path

Answer 9

Path from current directory (e.g., ../logs).

Question 10

Home directory

Answer 10

~ expands to the user’s home.

Question 11

Hidden files

Answer 11

Names starting with .; show with ls -a.

Question 12

Package manager (Debian)

Answer 12

apt, lower-level dpkg.

Question 13

Package manager (RHEL)

Answer 13

dnf/yum, lower-level rpm.

Question 14

Update packages (Debian)

Answer 14

sudo apt update && sudo apt upgrade.

Question 15

Install package (Debian)

Answer 15

sudo apt install <pkg>.

Question 16

Install package (RHEL)

Answer 16

sudo dnf install <pkg>.

Question 17

Filesystems

Answer 17

Common: ext4, xfs, btrfs.

Question 18

Inode

Answer 18

Metadata record for a file (owner, perms, timestamps, blocks).

Question 19

Hard link

Answer 19

Directory entry pointing to same inode; ln.

Question 20

Symbolic link

Answer 20

Pointer file to path; ln -s.

Question 21

View disk layout

Answer 21

lsblk, blkid, fdisk -l, parted -l.

Question 22

Make filesystem

Answer 22

mkfs.ext4 /dev/sdXn etc.

Question 23

Mount filesystem

Answer 23

mount /dev/sdXn /mnt.

Question 24

Persistent mounts

Answer 24

/etc/fstab entries.

Question 25

Swap

Answer 25

Virtual memory; check with `swapon --show`.

Question 26

LVM basics

Answer 26

`pvcreate`, `vgcreate`, `lvcreate`; mount `/dev//`.

Question 27

Check disk usage

Answer 27

`df -h` (filesystem), `du -sh *` (directory sizes).

Question 28

Permissions bits

Answer 28

r=4,w=2,x=1 for user, group, others.

Question 29

Change permissions

Answer 29

`chmod 750 file` or symbolic `chmod g+w`.

Question 30

Ownership

Answer 30

`chown user:group file`.

Question 31

Special bits

Answer 31

setuid, setgid, sticky; view with `ls -l` (+s/t).

Question 32

umask

Answer 32

Default permission mask; view/set with `umask`.

Question 33

ACLs

Answer 33

Fine‑grained perms: `getfacl`, `setfacl`.

Question 34

Users database

Answer 34

`/etc/passwd` (accounts), `/etc/shadow` (hashes).

Question 35

Groups database

Answer 35

`/etc/group`.

Question 36

Create user

Answer 36

`sudo adduser ` (Debian) or `useradd` (low‑level).

Question 37

Delete/lock user

Answer 37

`deluser` or `userdel`; lock with `usermod -L`.

Question 38

Modify user

Answer 38

`usermod -aG ` adds to group.

Question 39

Password aging

Answer 39

`chage -l `; set with `chage`.

Question 40

Create group

Answer 40

`groupadd `.

Question 41

Remove group

Answer 41

`groupdel `.

Question 42

List groups for user

Answer 42

`groups `.

Question 43

Switch user

Answer 43

`su - `; to root with `sudo -i` if allowed.

Question 44

sudo

Answer 44

Privilege escalation per `/etc/sudoers`; edit with `visudo`.

Question 45

PAM

Answer 45

Pluggable Authentication Modules control auth policies.

Question 46

Process listing

Answer 46

`ps aux`, `top`, `htop`.

Question 47

Signals

Answer 47

Terminate with `kill `; SIGKILL `-9`, SIGTERM `-15`.

Question 48

Job control

Answer 48

`&`, `jobs`, `bg`, `fg`, `Ctrl+Z`.

Question 49

Priorities

Answer 49

`nice` sets, `renice` changes niceness.

Question 50

Background survival

Answer 50

`nohup cmd &` or `disown`.

Question 51

Systemd service control

Answer 51

`systemctl start|stop|restart|status `.

Question 52

Enable at boot

Answer 52

`systemctl enable `; disable with `disable`.

Question 53

Targets (runlevels)

Answer 53

`systemctl get-default`/`set-default`.

Question 54

Logs (journald)

Answer 54

`journalctl -u `; follow with `-f`.

Question 55

Traditional logs

Answer 55

Files under `/var/log/` (e.g., `auth.log`, `syslog`, `secure`).

Question 56

Crontab

Answer 56

Schedule with `crontab -e`; format: m h dom mon dow cmd.

Question 57

System‑wide cron

Answer 57

`/etc/crontab`, `/etc/cron.*`.

Question 58

At jobs

Answer 58

One‑time run: `at 22:00` then commands, end with `Ctrl+D`.

Question 59

Time sync

Answer 59

`timedatectl` and `chrony`/`systemd-timesyncd`.

Question 60

Networking basics

Answer 60

Show IP: `ip addr`; routes: `ip route`.

Question 61

Test connectivity

Answer 61

`ping`, `traceroute`/`tracepath`.

Question 62

Name resolution

Answer 62

`/etc/hosts`, `/etc/resolv.conf`, `nsswitch.conf`; test with `dig`/`nslookup`/`host`.

Question 63

Open ports

Answer 63

`ss -tuln` or `netstat -tuln`.

Question 64

SSH client

Answer 64

`ssh user@host`.

Question 65

SSH keys

Answer 65

Generate `ssh-keygen`; copy with `ssh-copy-id`.

Question 66

File transfer

Answer 66

`scp`, `sftp`, `rsync -av`.

Question 67

Firewall (UFW)

Answer 67

`ufw enable`; `ufw allow 22/tcp`; `ufw status verbose`.

Question 68

FirewallD

Answer 68

`firewall-cmd --add-service=ssh --permanent && --reload`.

Question 69

SELinux/AppArmor

Answer 69

Mandatory access control frameworks; tune via policies.

Question 70

Text viewing

Answer 70

`cat`, `less`, `head`, `tail -f`.

Question 71

Search text

Answer 71

`grep -R`, `egrep`, ripgrep `rg`.

Question 72

Find files

Answer 72

`find /path -type f -name '*.log'`.

Question 73

Locate db

Answer 73

`updatedb`; search with `locate`.

Question 74

Redirection

Answer 74

`>`, `>>`, `2>`, `&>`, `tee`.

Question 75

Pipes

Answer 75

`|` sends stdout of left command to right command.

Question 76

Editors

Answer 76

`nano`, `vim`, `ed`.

Question 77

Compression

Answer 77

`tar`, `gzip`, `bzip2`, `xz`; e.g., `tar czf backup.tgz dir/`.

Question 78

Environment vars

Answer 78

`printenv`, set `VAR=value cmd`, export with `export VAR=value`.

Question 79

Bash expansion

Answer 79

Globbing `* ? []`; brace `{a,b}`; command `$(...)`.

Question 80

History

Answer 80

`history`, rerun with `!n` or `!!`.

Question 81

Timestamps

Answer 81

`stat file` shows atime, mtime, ctime.

Question 82

System info

Answer 82

`uname -a`, `lsb_release -a`, `hostnamectl`.

Question 83

Hardware info

Answer 83

`lscpu`, `lsmem`, `lspci`, `lsusb`, `dmidecode`.

Question 84

Kernel modules

Answer 84

`lsmod`, `modprobe`, `rmmod`.

Question 85

Bootloader

Answer 85

GRUB; edit `/etc/default/grub`, update with `update-grub`.

Question 86

Rescue/emergency

Answer 86

Boot to rescue target; `systemctl rescue`.

Question 87

Backups

Answer 87

`rsync`, `tar`; verify and test restores.

Question 88

Security updates

Answer 88

Apply promptly; consider unattended‑upgrades (Debian).

Question 89

Logs for auth

Answer 89

Debian: `/var/log/auth.log`; RHEL: `/var/log/secure`.

Question 90

File integrity

Answer 90

`sha256sum file` to verify checksums.

Question 91

Networking config tools

Answer 91

`nmcli` on NetworkManager systems.

Question 92

Host keys vs user keys

Answer 92

Server identity in `/etc/ssh/ssh_host_*`; user creds in `~/.ssh/`.

Question 93

SSH hardening

Answer 93

Disable root login, use keys, set `AllowUsers`, change `PasswordAuthentication` to `no`.

Question 94

Name services order

Answer 94

`/etc/nsswitch.conf` controls lookup sequence.

Question 95

System resource monitors

Answer 95

`top`, `htop`, `iostat`, `vmstat`, `sar`.

Question 96

Space hogs

Answer 96

`du -xhd1 /` to find large dirs (Debian syntax).

Question 97

Tar extract

Answer 97

`tar xzf archive.tgz -C /target`.

Question 98

Grep regex basics

Answer 98

`.` any char; `^` start; `$` end; `*` 0+; `+` 1+; `?` 0/1; `[]` class.