src/Doc/System/Misc.thy

   \<^medskip>
   Option \<^verbatim>\<open>-B\<close> specifies the Docker image taken as starting point for the
   Isabelle installation: it needs to be a suitable version of Ubuntu Linux.
   The default \<^verbatim>\<open>ubuntu\<close> refers to the latest LTS version provided by Canonical
   as the official Ubuntu vendor\<^footnote>\<open>\<^url>\<open>https://hub.docker.com/_/ubuntu\<close>\<close>. For
-  Isabelle2020 this should be Ubuntu 18.04 LTS.
+  Isabelle2021 this should be Ubuntu 20.04 LTS.
 
   Option \<^verbatim>\<open>-p\<close> includes additional Ubuntu packages, using the terminology
   of \<^verbatim>\<open>apt-get install\<close> within the underlying Linux distribution.
 
   Option \<^verbatim>\<open>-P\<close> refers to high-level package collections: \<^verbatim>\<open>X11\<close> or \<^verbatim>\<open>latex\<close> as

 
 text \<open>
   Produce a Dockerfile (without image) from a remote Isabelle distribution:
   @{verbatim [display]
 \<open>  isabelle build_docker -E -n -o Dockerfile
-    https://isabelle.in.tum.de/website-Isabelle2020/dist/Isabelle2020_linux.tar.gz\<close>}
+    https://isabelle.in.tum.de/website-Isabelle2021/dist/Isabelle2021_linux.tar.gz\<close>}
 
   Build a standard Isabelle Docker image from a local Isabelle distribution,
   with \<^verbatim>\<open>bin/isabelle\<close> as executable entry point:
 
   @{verbatim [display]
-\<open>  isabelle build_docker -E -t test/isabelle:Isabelle2020 Isabelle2020_linux.tar.gz\<close>}
+\<open>  isabelle build_docker -E -t test/isabelle:Isabelle2021 Isabelle2021_linux.tar.gz\<close>}
 
   Invoke the raw Isabelle/ML process within that image:
   @{verbatim [display]
-\<open>  docker run test/isabelle:Isabelle2020 process -e "Session.welcome ()"\<close>}
+\<open>  docker run test/isabelle:Isabelle2021 process -e "Session.welcome ()"\<close>}
 
   Invoke a Linux command-line tool within the contained Isabelle system
   environment:
   @{verbatim [display]
-\<open>  docker run test/isabelle:Isabelle2020 env uname -a\<close>}
+\<open>  docker run test/isabelle:Isabelle2021 env uname -a\<close>}
   The latter should always report a Linux operating system, even when running
   on Windows or macOS.
 \<close>
 
 

 
   Display Isabelle version information.\<close>}
 
   \<^medskip>
   The default is to output the full version string of the Isabelle
-  distribution, e.g.\ ``\<^verbatim>\<open>Isabelle2020: April 2020\<close>.
+  distribution, e.g.\ ``\<^verbatim>\<open>Isabelle2021: February 2021\<close>.
 
   The \<^verbatim>\<open>-i\<close> option produces a short identification derived from the Mercurial
   id of the @{setting ISABELLE_HOME} directory.
 \<close>