les folders principaux

/bin → binary (executable des commandes essenciel)

/boot → bootstrap (fichier statique chargeur d’amorçage)

/etc → editing text config (fichier de configuration)

/dev → device

/lost and found → dossier de la commande fsck

/opt → application hors gestionnaire de paquet

   /mnt → mount

/run → runtime system (info relative au system depuis son dernier reboot)

/sbin → super binary (exe system essentiels)

/srv → service (data pour les services du system)

/usr → Unix system ressources

/var → variable

en vrac

telnet → pour le troubleshooting network

neofetch → paquet pour avoir les infos du poste

init → 1er process sur les distributions ubuntu

dmesg → log du boot

umask → droits chown - umask (exemple: 777 - 222 = 444)

commande whereis est différente de locate

Shabang

-xe: mode debug

Hostnamectl

hostnamectl status

Cut

cut -d: -f1

-d delimiter

-f fields

Grep (Globale/REgular/Expression/Print)

grep -E: egrep

grep -F: fgrep

grep -r: rgrep

grep toto /tmp/*

-r récursif

-i no key sensitive

Sed (Stream EDitor)

SED command in UNIX stands for stream editor and it can perform lots of functions on file like searching, find and replace, insertion or deletion.

sed -i.bck 's/unix/linux/' toto.txt : Replacing or substituting string

sed -i.bck 's/unix/linux/2' toto.txt : Replacing the nth occurrence of a pattern in a line

sed -i.bck 's/unix/linux/g' toto.txt : Replacing all the occurrence of the pattern in a line

sed -i.bck '3 s/unix/linux/' toto.txt : Replacing string on a specific line number

sed -i.bck '1,3 s/unix/linux/' toto.txt : Replacing string on a range of lines

sed -i.bck -n 's/unix/linux/p' toto.txt : Printing only the replaced lines

sed -i.bck '/tata/d' toto.txt: delete line with the occurrence

sed '5d' filename.txt: delete the nth line

sed '$d' filename.txt: delete the last line

sed '3,6d' filename.txt delete between the 3th to 6th line

Rsync

rsync -av toto root@machine:/tmp

-a archive

-v verbose

ln

ln -s /pt d’arriver /pt départ

awk

Troubleshoot linux

free -h

du -sh

cat /var/log/messages

cat /var/log/secure

htop -u toto: Cette commande permet d’afficher les processus d’un utilisateur.

htop -t: tree