~$ cat admsys/cheatsheet.md_

Cheat Sheet
Administration Systeme

Commandes essentielles des 4 modules — version unifiee pour revision d'examen

grub2disquesutilisateursnetwork UEFILVMPAM
check config system danger
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01 — GRUB2 & UEFI
Boot mode, update-grub, efibootmgr, chroot
02 — Disques & LVM
lsblk, fdisk, mkfs, fstab, LVM
03 — Utilisateurs & Groupes
useradd, usermod, passwd, chage, PAM
04 — Network Manager
nmcli, ip, DNS, diag
module 01
GRUB2 & UEFI

Check rapide

# mode boot
[ -d /sys/firmware/efi ] && echo "UEFI" || echo "BIOS legacy"
# entrées UEFI
sudo efibootmgr -v

Config minimale

# editer /etc/default/grub
sudo nano /etc/default/grub
# appliquer
sudo update-grub
rappelNe jamais editer /boot/grub/grub.cfg directement.

Reparer (chroot)

lsblk -f
sudo mount /dev/sda2 /mnt
sudo mount /dev/sda1 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount --bind $i /mnt$i; done
sudo chroot /mnt
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=ubuntu
update-grub

grub rescue>

grub rescue> ls
grub rescue> set root=(hd0,gpt2)
grub rescue> set prefix=(hd0,gpt2)/boot/grub
grub rescue> insmod normal
grub rescue> normal
module 02
Disques, Partitions, LVM

Decouverte

lsblk -f
df -h
sudo blkid

Partition + format

sudo fdisk /dev/sdb
sudo partprobe /dev/sdb
sudo mkfs.ext4 /dev/sdb1

Montage & fstab

sudo mount /dev/sdb1 /mnt/data
sudo umount /mnt/data
sudo mount -a
formatUUID=... /mnt/data ext4 defaults 0 2

LVM essentiel

sudo pvcreate /dev/sdb1
sudo vgcreate vg0 /dev/sdb1
sudo lvcreate -L 10G -n lv-data vg0
sudo lvextend -l +100%FREE /dev/vg0/lv-data
sudo resize2fs /dev/vg0/lv-data
module 03
Utilisateurs & Groupes

Verifier

id
getent passwd robert
getent group sudo

Comptes

sudo useradd -m -s /bin/bash -G sudo robert
sudo passwd robert
sudo usermod -aG sudo robert
sudo userdel -r robert
piegeToujours -aG pour ajouter un groupe a un user.

Groupes

sudo groupadd devteam
sudo gpasswd -a robert devteam
sudo gpasswd -d robert devteam

Expiration / PAM

sudo chage -l robert
sudo chage -M 90 -W 14 robert
sudo nano /etc/security/pwquality.conf
module 04
Network Manager & Diagnostics

Etat & profils

nmcli device status
nmcli connection show
sudo nmcli connection up "Wired connection 1"
sudo nmcli connection down "Wired connection 1"
notenmcli = persistant. ip = temporaire.

WiFi

nmcli device wifi list
sudo nmcli device wifi connect "SSID" password "mdp"

IP & routes

ip addr show
ip route show
ip route add default via 192.168.1.1

DNS & diag

nslookup google.com
ping -c 3 8.8.8.8
sudo journalctl -u NetworkManager -n 50