diff --git a/README.md b/README.md
index d206c03..5905faf 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,17 @@
 # renew_cert
 
-A shell script used to renew let’s encrypt certificates
\ No newline at end of file
+A shell script used to renew let’s encrypt certificates
+
+## CSR creation
+### For only one domain
+
+```
+	openssl req -nodes -newkey rsa:4096 -sha256 -keyout bulbizarre.swordarmor.fr.key -out bulbizarre.swordarmor.fr.csr
+```
+
+### For multiple domains
+
+```
+	openssl req -new -sha512 -key ix.bzh.key -subj "/" -reqexts SAN -config < (cat /etc/ssl/openssl.cnf < (printf "[SAN]\nsubjectAltName=DNS:ix.bzh,DNS:www.ix.bzh")) > ix.bzh.csr
+```
+