====== Linux Commands ======

Below are a list of useful Linux commands

==== Find release version of Linux ====

<code>
lsb_release -a

</code>

==== Append contents within file ====

<code>
cat <<EOF | tee -a /etc/ssh/sshd_config
permitrootlogon yes
EOF

</code>

==== Replace contents within a file ====
<code>

cat <<EOF | tee /etc/ssh/sshd_config
permitrootlogon yes
EOF

</code>

==== Find and Replace contents within a file ====
<code>

sed -i 's/PermitRootLogin no/PermitRootLogin yes/' /etc/ssh/sshd_config

</code>

==== Change directory back one level to another folder ====

<code>
cd ../test2

</code>

==== Delete folder ====

<code>
rm -rf folder

</code>

==== Delete file ====

<code>
rm file

</code>

==== Copy files within one folder to another ====

<code>
cp * ../test2

</code>

==== Create empty file ====

<code>
touch filename

</code>

==== Find out if a website supports HTTP2 Protocol ====

<code>
curl -I --http2 -s http://coffee.orionmail.org | grep HTTP

</code>

==== Check HTTP Header ====
<code>

curl -vs http://coffee.orionmail.org

</code>

==== Ensure APT packages cannot be auto-updated ====

<code>
apt-mark hold kubeadm kubelet kubectl

</code>

==== See status of a Service ====

<code>
systemctl status docker

</code>

==== Restart service ====

<code>
systemctl restart docker

</code>

==== User GREP to find text within a file ====

<code>
cat /etc/ssh/sshd_config | grep permit

</code>

==== Find file in File System ====
<code>

find / -name sasl_passwd

</code>

==== Disk Usage for Folders ====

<code>
du -shc

</code>

s Displays the total size for the Directory. It does not display the totals for subdirectories

h Prints sizes in human readable format

c Prints grant total for all sizes