added instructions to format usb

tutos/computer.txt

@@ -56,3 +56,32 @@
 	**sudo update-alternatives --config x-www-browser**
 	**sudo update-alternatives --config gnome-www-browser**
 
+**change dns :**
+	https://learnubuntu.com/change-dns-server/
+	so far i just changed in /etc/resolv.conf
+
+**format usb :**
+	- list disk :
+		**df -h** mounted partitions, or
+		**lsblk** or
+		**sudo fdisk -l** for more informations
+	- unmount partitions :
+	**sudo umount /dev/sdb1** unmount usb, replace /dev/sdb1 with name of your usb
+	- if necessary, erase all memory :
+	**sudo dd if=/dev/zero of=/dev/sdb bs=4k status=progress && sync** sync to flush the cache
+	- if necessary, erase all partitions or create new ones :
+	**sudo fdisk /dev/sdb**
+		> Command (m for help): **o** for creating an empty partition table
+		> Command (m for help): **n** for creating a new one
+			> Select (default p): **<enter>** to select default p
+			> Partition number (default 1): **<enter>** to create a partition number 1
+			> First sector (default 2048): **<enter>** to start partition at begining
+			> Last sector (default xxxxxxxx): **<enter>** to give partition full size
+		> Command (m for help): **w** to write the changes (before that, nothing was really made)
+	- format partitions (re list before) :
+	**sudo mkfs -t vfat -n "<name>" /dev/sdb1** to format in fat32 (vfat) (MaKe FileSystem)
+
+**list of automatic settings :**
+	- change dns
+	- configure firefox addons
+	-