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% Document Info
\author{Anthony.Dominguez}
\pdfinfo{
  /Title (learning-ssh-2.pdf)
  /Creator (Cheatography)
  /Author (Anthony.Dominguez)
  /Subject (Learning SSH 2 Cheat Sheet)
}

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\fancyhead[L]{
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{C}
    \SetRowColor{DarkBackground}
    \vspace{-7pt}
    {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent
        \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}}
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\columnbreak
\begin{tabulary}{11cm}{L}
    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Learning SSH 2 Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{Anthony.Dominguez} via \textcolor{DarkBackground}{\uline{cheatography.com/202519/cs/43019/}}}
\end{tabulary}
\end{multicols}}

\fancyfoot[L]{ \footnotesize
\noindent
\begin{multicols}{3}
\begin{tabulary}{5.8cm}{LL}
  \SetRowColor{FootBackground}
  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}Anthony.Dominguez \\
  \uline{cheatography.com/anthony-dominguez} \\
  \end{tabulary}
\vfill
\columnbreak
\begin{tabulary}{5.8cm}{L}
  \SetRowColor{FootBackground}
  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Not Yet Published.\\
   Updated 22nd April, 2024.\\
   Page {\thepage} of \pageref{LastPage}.
\end{tabulary}
\vfill
\columnbreak
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}}  \\
  \SetRowColor{white}
  \vspace{-5pt}
  %\includegraphics[width=48px,height=48px]{dave.jpeg}
  Measure your website readability!\\
  www.readability-score.com
\end{tabulary}
\end{multicols}}




\begin{document}
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\begin{multicols*}{2}

\begin{tabularx}{8.4cm}{x{1.584 cm} x{0.864 cm} x{1.584 cm} x{3.168 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Installing OpenSSH}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Options}} & {\bf{Arguments}} & {\bf{Arguments}} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{sudo apt}} &  & update & Check for updated package definitions \tn 
% Row Count 6 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{sudo apt install}} &  & \seqsplit{opens-server} & Install OpenSSH server \tn 
% Row Count 9 (+ 3)
% Row 3
\SetRowColor{white}
{\bf{sudo systemctl}} &  & status sshd & Information about SSH configuration \tn 
% Row Count 12 (+ 3)
% Row 4
\SetRowColor{LightBackground}
{\bf{sudo ufw}} &  & status & Check firewall status and rules \tn 
% Row Count 14 (+ 2)
% Row 5
\SetRowColor{white}
{\bf{sudo ufw}} &  & allow ssh & Allows SSH traffic through the firewall \tn 
% Row Count 17 (+ 3)
% Row 6
\SetRowColor{LightBackground}
{\bf{sudo ufw}} &  & enable & Enables firewall \tn 
% Row Count 19 (+ 2)
% Row 7
\SetRowColor{white}
{\bf{sudo nano}} &  & \seqsplit{/etc/ssh/sshd\_config} & Allows editing the SSH server configuration \tn 
% Row Count 22 (+ 3)
% Row 8
\SetRowColor{LightBackground}
{\bf{sudo nano}} &  & \seqsplit{/etc/ssh/ssh\_config} & Allows editing the SSH client configuration \tn 
% Row Count 25 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{By default, SSH runs in port 22 using TCP protocol \newline SSH server configuration is stored in /etc/ssh/sshd\_config. \newline SSH client configuration is stored in /etc/ssh/ssh\_config.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.672 cm} x{1.9 cm} x{4.028 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{8.4cm}}{\bf\textcolor{white}{Managing Users and Access}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Argument}} & {\bf{Description}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
{\bf{AllowUser}} & leigh vishal stefan & Only allow these users to log in \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
{\bf{DenyUser}} & bob mary paulina & Allow all users except these \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
{\bf{AllowGroup}} & admins \seqsplit{developers} & Only allow users in these groups to log in \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
{\bf{DenyGroup}} & sales marketing & Allow all users except those in this groups \tn 
% Row Count 11 (+ 3)
% Row 5
\SetRowColor{white}
{\bf{Match Address}} & \seqsplit{10.0.1.0/24} & To be able to connect remotely only from 10.0.1.0/24 addresses \tn 
% Row Count 14 (+ 3)
% Row 6
\SetRowColor{LightBackground}
{\bf{Match User}} & alice bob & Alice and bob are able to connect remotely according to subsequent parameters \tn 
% Row Count 18 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{8.4cm}}{All the information above is available in the file /etc/ssh/sshd\_config \newline Precedence matters when defining access}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.292 cm} x{2.736 cm} x{3.572 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{3}{x{8.4cm}}{\bf\textcolor{white}{Connecting to a server using a password}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Arguments}} & {\bf{Description}} \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
{\bf{ssh}} & {\emph{username}}@{\emph{ip address}} & Connect to a remote SSH server \tn 
% Row Count 4 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\SetRowColor{LightBackground}
\mymulticolumn{3}{x{8.4cm}}{The first time connection is established to a remote SSH server, a host fingerprint is indicated in the screen, and if the fingerprint is accepted, the local device saves the fingerprint together with information about the connection into a folder into the file /home/ssh/known\_hosts}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}---}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{3.76 cm} x{4.24 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Creating a key pair with ssh-keygen}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & **Description \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
{\bf{ssh-keygen}} & Generate public/private rsa key pair. \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
{\bf{ssh-keyscan}} {\emph{server ip address}} & Displays keys to share depending on the encryption algorithm to be used. \tn 
% Row Count 7 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{It is recommended to generate a key pair for only one purpose (one user/one server). It is also recommended to save the keys in separate folders in the /home/{\emph{user}}/.ssh/ directory. A passphrase can also be added as an extra layer of security for the key pair.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
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\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Managing and using key pairs}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Description}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
ssh-copy-id -i \textasciitilde{}/.ssh/{\emph{mykey}}.pub {\emph{user}}@{\emph{server}} & Add key to \textasciitilde{}/.ssh/authorized\_keys if access to ssh server already exists \tn 
% Row Count 5 (+ 4)
% Row 2
\SetRowColor{LightBackground}
Add key to \textasciitilde{}/.ssh/authorized\_keys out of band & Add key to \textasciitilde{}/.ssh/authorized\_keys if access to ssh server does not exists \tn 
% Row Count 9 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{When changing the configuration of \textasciitilde{}/etc/ssh/sshd\_config with nano, remember to restart the service for the new settings to apply, with {\bf{sudo systemctl restart}} sshd. \newline When having a lot of keys, we can speed up the connection process by specifying which key we want to use to connect to the server, like: {\bf{ssh}} {\emph{user}}@{\emph{server}} -i \textasciitilde{}/.ssh/{\emph{key directory}}}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{p{0.8 cm} x{7.2 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Client Configuration Options}}  \tn
% Row 0
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{Host {\emph{name}}} \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
 & Hostname {\emph{ip address}} \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
 & Port {\emph{port number}} \tn 
% Row Count 3 (+ 1)
% Row 3
\SetRowColor{white}
 & User {\emph{username}} \tn 
% Row Count 4 (+ 1)
% Row 4
\SetRowColor{LightBackground}
 & IdentityFile \textasciitilde{}/.ssh/{\emph{key name}} \tn 
% Row Count 5 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{For information about precedence's and priorities, consult {\bf{man}} ssh\_config. SSH obtains configuration data from the following sources in the following order: \newline            1.   command-line options \newline            2.   user's configuration file (\textasciitilde{}/.ssh/config) \newline            3.   system-wide configuration file (/etc/ssh/ssh\_config) \newline  \newline It is also good practice to change \textasciitilde{}/.ssh/config to be only read and write by the user with {\bf{chmod}} 600 \textasciitilde{}/.ssh/config}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{0.936 cm} x{1.152 cm} x{1.656 cm} x{3.456 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Transferring Files with SFTP}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{sftp}} &  & {\emph{user}}@{\emph{ip address}} & Initiate SFTP connection with remote server. \tn 
% Row Count 6 (+ 3)
% Row 2
\SetRowColor{LightBackground}
{\bf{bye}} &  &  & Terminates SFTP connection to remote server. \tn 
% Row Count 9 (+ 3)
% Row 3
\SetRowColor{white}
{\bf{help}} &  &  & Shows a list of available commands while in SFTP mode, including commands to change working directories. \tn 
% Row Count 15 (+ 6)
% Row 4
\SetRowColor{LightBackground}
{\bf{put}} &  & {\emph{file name}} & Sends a file from the local working directory to the remote local directory. \tn 
% Row Count 19 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{0.864 cm} x{0.864 cm} x{2.736 cm} x{2.736 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Transferring Files with SCP}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{{\emph{Command}}}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
{\bf{scp}} &  & {\emph{local file name}} {\emph{user}}@{\emph{ip address}}: & Copies a file from the local working directory to the remote working directory. \tn 
% Row Count 10 (+ 6)
% Row 2
\SetRowColor{LightBackground}
{\bf{scp}} &  & {\emph{user}}@{\emph{ip address}}:{\emph{remote file name}} {\emph{local file name}} & Copies a file from the remote working directory to the local working directory. \tn 
% Row Count 16 (+ 6)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{The colon represents the remote user home directory, and both relative and absolute paths can be used to refer to a different directory than the home directory.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{p{0.72 cm} x{2.016 cm} x{2.232 cm} x{2.232 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Multi-Step SSH Connections}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{ssh}} & -J & {\emph{user}}@{\emph{server1}},{\emph{user}}@{\emph{server2}} {\emph{user}}@{\emph{server3}} & Enable multi-step SSH connection by providing the credentials to all \seqsplit{intermediate} and the final server to be accessed, without manually \seqsplit{establishing} all connections separately. \tn 
% Row Count 18 (+ 15)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{} \tn 
% Row Count 18 (+ 0)
% Row 3
\SetRowColor{white}
\mymulticolumn{4}{x{8.4cm}}{Host myserver} \tn 
% Row Count 19 (+ 1)
% Row 4
\SetRowColor{LightBackground}
 & Hostname {\emph{ip address}} &  &  \tn 
% Row Count 21 (+ 2)
% Row 5
\SetRowColor{white}
 & Port {\emph{port number}} &  &  \tn 
% Row Count 23 (+ 2)
% Row 6
\SetRowColor{LightBackground}
 & User {\emph{username}} &  &  \tn 
% Row Count 25 (+ 2)
% Row 7
\SetRowColor{white}
 & \seqsplit{IdentityFile} \textasciitilde{}/.ssh/{\emph{key name}} &  &  \tn 
% Row Count 28 (+ 3)
% Row 8
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{} \tn 
% Row Count 28 (+ 0)
% Row 9
\SetRowColor{white}
\mymulticolumn{4}{x{8.4cm}}{Host server2} \tn 
% Row Count 29 (+ 1)
% Row 10
\SetRowColor{LightBackground}
 & Hostname {\emph{ip address}} &  &  \tn 
% Row Count 31 (+ 2)
\end{tabularx}
\par\addvspace{1.3em}

\vfill
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\begin{tabularx}{8.4cm}{p{0.72 cm} x{2.016 cm} x{2.232 cm} x{2.232 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Multi-Step SSH Connections (cont)}}  \tn
% Row 11
\SetRowColor{LightBackground}
 & ProxyJump {\emph{user}}@{\emph{ip address of myserver}} &  &  \tn 
% Row Count 4 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.224 cm} x{0.864 cm} x{2.52 cm} x{2.592 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Port Forwarding with SSH}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{Command}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
{\bf{ssh}} & -L & {\emph{{[}bind\_addr:{]}}}{\emph{port}}:{\emph{host}}:{\emph{port}} {\emph{user}}@{\emph{ip address}} & Local port forwarding. \tn 
% Row Count 8 (+ 4)
% Row 2
\SetRowColor{LightBackground}
{\bf{ssh}} & -R & {\emph{{[}bind\_addr:{]}}}{\emph{port}}:{\emph{host}}:{\emph{port}} & Remote port forwarding. \tn 
% Row Count 11 (+ 3)
% Row 3
\SetRowColor{white}
{\bf{ssh}} & -D & {\emph{{[}bind\_addr:{]}}}{\emph{port}} & Dynamic port forwarding. \tn 
% Row Count 13 (+ 2)
% Row 4
\SetRowColor{LightBackground}
 & -f &  & Fork the SSH process into the background \tn 
% Row Count 16 (+ 3)
% Row 5
\SetRowColor{white}
 & -n &  & Don't read from STDIN. \tn 
% Row Count 18 (+ 2)
% Row 6
\SetRowColor{LightBackground}
 & -N &  & Don't run remote commands. \tn 
% Row Count 20 (+ 2)
% Row 7
\SetRowColor{white}
 & -T &  & Don't allocate a TTY \tn 
% Row Count 22 (+ 2)
% Row 8
\SetRowColor{LightBackground}
{\bf{ps x}} | {\bf{grep}} &  & ssh & Find processes owned by the user, including those without a controlling terminal \tn 
% Row Count 28 (+ 6)
% Row 9
\SetRowColor{white}
{\emph{kill}} &  & {\emph{process port}} & Ends the process that belongs to a process port. \tn 
% Row Count 32 (+ 4)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{Port forwarding can also be configured in the client file \textasciitilde{}/.ssh/config \newline ... \newline Host server1 \newline \textbackslash{}t{\bf{Hostname}} 10.0.1.110 \newline \textbackslash{}t\# Access remote port 3306 through local port 3333 \newline \textbackslash{}t{\bf{LocalForward}} 3333:localhost:3306 \newline \textbackslash{}t\# Access local port 22 through remote port 5432 \newline \textbackslash{}t{\bf{RemoteForward}} 22:localhost:5432 \newline \textbackslash{}t\# Starts a SOCKS proxy on local port 3000 \newline \textbackslash{}t{\bf{DynamicForward}} 3000}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.368 cm} x{1.08 cm} x{1.296 cm} x{3.456 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Troubleshooting SSH}}  \tn
% Row 0
\SetRowColor{LightBackground}
{\bf{{\emph{Command}}}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
{\bf{systemctl}} & \seqsplit{status} & sshd & Check the status of the SSH service. \tn 
% Row Count 5 (+ 2)
% Row 2
\SetRowColor{LightBackground}
{\bf{systemctl}} & \seqsplit{restart} & sshd & Restarts the SSH service. \tn 
% Row Count 7 (+ 2)
% Row 3
\SetRowColor{white}
{\bf{journalctl}} & -u & ssh & See the log for SSH services, to look at problems. \tn 
% Row Count 10 (+ 3)
% Row 4
\SetRowColor{LightBackground}
{\bf{sudo ufw}} &  & status & Looks at the rules set for the firewall. \tn 
% Row Count 13 (+ 3)
% Row 5
\SetRowColor{white}
{\bf{sudo cat}} &  & \seqsplit{/etc/shadow/} & Looks at the shadow file. \tn 
% Row Count 15 (+ 2)
% Row 6
\SetRowColor{LightBackground}
| {\bf{grep}} &  & {\emph{username}} & Pipes the search with grep to look for the username, if there is an exclamation mark at the beginning of the password field, that means the user is locked. \tn 
% Row Count 24 (+ 9)
% Row 7
\SetRowColor{white}
{\bf{sudo usermod}} & -U & {\emph{username}} & Unlocks the locked user account. \tn 
% Row Count 27 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
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\begin{tabularx}{8.4cm}{x{4 cm} x{4 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{8.4cm}}{\bf\textcolor{white}{Securing a SSH Server}}  \tn
% Row 0
\SetRowColor{LightBackground}
1) Don't allow the root user to log in & {\bf{PermitRootLogin}} no (or {\bf{prohibit-password}}) \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
2) Prevent password logins, and allow keys & {\bf{PasswordAuthentication}} no\{\{nl\}\}{\bf{PubKeyAuthentication}} yes \tn 
% Row Count 7 (+ 4)
% Row 2
\SetRowColor{LightBackground}
3) Change the service port & {\bf{Port}} {\emph{port number}} \tn 
% Row Count 9 (+ 2)
% Row 3
\SetRowColor{white}
4) Change the encryption ciphers the server allows & {\bf{Ciphers}} ... (see {\bf{man}} sshd\_config) \tn 
% Row Count 12 (+ 3)
% Row 4
\SetRowColor{LightBackground}
5) Enact user control & {\bf{AllowUser}}\{\{nl\}\}{\bf{DenyUser}}\{\{nl\}\}{\bf{AllowGroup}}\{\{nl\}\}{\bf{DenyGroup}} \tn 
% Row Count 16 (+ 4)
% Row 5
\SetRowColor{white}
\mymulticolumn{2}{x{8.4cm}}{6) Consider using software like Fail2ban to help prevent repeated malicious login attempts} \tn 
% Row Count 18 (+ 2)
% Row 6
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{8.4cm}}{7) Consider designing your system to use a bastion host} \tn 
% Row Count 20 (+ 2)
% Row 7
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\mymulticolumn{2}{x{8.4cm}}{8) Consider putting your SSH server or bastion host behind a VPN} \tn 
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\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{8.4cm}{x{1.584 cm} x{1.008 cm} x{1.512 cm} x{3.096 cm} }
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\mymulticolumn{4}{x{8.4cm}}{\bf\textcolor{white}{Tools That Use SSH (Mosh, Mobile Shell)}}  \tn
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{\bf{{\emph{Command}}}} & {\bf{Option(s)}} & {\bf{Argument(s)}} & {\bf{Description}} \tn 
% Row Count 3 (+ 3)
% Row 1
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{\bf{sudo apt install}} &  & mosh & Install Mosh (needed in both the client and the server) \tn 
% Row Count 7 (+ 4)
% Row 2
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{\bf{sudo ufw}} & allow & \seqsplit{60001/udp} & Opens ports for Mosh (in the 60,000 range, only needed in the server). \tn 
% Row Count 12 (+ 5)
% Row 3
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{\bf{mosh}} &  & {\emph{user}}@{\emph{ip address}} & Starts a Mosh session, just like a SSH connection. \tn 
% Row Count 15 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\SetRowColor{LightBackground}
\mymulticolumn{4}{x{8.4cm}}{Mosh provides a fault-tolerant shell experience. Mosh has to be configured in both the client and the server.}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}----}
\end{tabularx}
\par\addvspace{1.3em}


% That's all folks
\end{multicols*}

\end{document}