Added linux owner rights commands.

applications/lofar2/doc/prestudy/desp_howtools_erko.txt

@@ -417,6 +417,9 @@ Host *
 Host astron
     User kooistra
     HostName portal.astron.nl
+Host dop386
+    User kooistra
+    ProxyCommand ssh -q -A astron netcat 10.87.0.228 22
 Host dop428
     User hiemstra
     ProxyCommand ssh -q -A astron netcat 10.87.0.228 22
@@ -613,6 +616,8 @@ Quartus version meeting minutes 13 may 2020 (RW, LH JH, EK):
 * Linux
 *******************************************************************************
 
+https://linuxize.com/
+
 dop466 = SSD
 dop466_0 = HDD
 
@@ -630,3 +635,17 @@ apt-get upgrade
 apt-get dist-upgrade
 apt remove
 
+# primary group
+# supplementary groups
+
+groups kooistra           # lists in which Linux groups I am a member of
+id kooistra               # lists in which Linux groups I am a member of
+getent group sudo         # lists which users are in the sudo Linux group
+more /etc/group
+sudo groupadd software                 # add new Linux group 'software'
+sudo usermod -a -G software kooistra   # add user 'kooistra' to a Linux group 'software'
+
+ls -l filename                  # shows current user,group owners of the 'filename'
+sudo chgrp software filename    # change group of 'filename' to 'software'
+sudo chgrp -R software dirname  # recursively change group of 'dirname' to 'software'
+#chown                          # change user,group