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% Document Info
\author{nhatlong0605}
\pdfinfo{
  /Title (lfcs-module4-operatingrunningsystems.pdf)
  /Creator (Cheatography)
  /Author (nhatlong0605)
  /Subject (LFCS\_Module4\_OperatingRunningSystems Cheat Sheet)
}

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    {\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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    \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{LFCS\_Module4\_OperatingRunningSystems Cheat Sheet}}}} \\
    \normalsize{by \textcolor{DarkBackground}{nhatlong0605} via \textcolor{DarkBackground}{\uline{cheatography.com/68292/cs/17215/}}}
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  \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}}  \\
  \vspace{-2pt}nhatlong0605 \\
  \uline{cheatography.com/nhatlong0605} \\
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  \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}}  \\
   \vspace{-2pt}Published 25th September, 2018.\\
   Updated 6th April, 2020.\\
   Page {\thepage} of \pageref{LastPage}.
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  Measure your website readability!\\
  www.readability-score.com
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\begin{multicols*}{3}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Boot order}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{p{5.377cm}}{\vspace{1px}\centerline{\includegraphics[width=5.1cm]{/web/www.cheatography.com/public/uploads/nhatlong0605_1537858731_Capture.JPG}}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.64241 cm} x{3.33459 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Process Properties w/ ps}}  \tn
% Row 0
\SetRowColor{LightBackground}
\seqsplit{PID-VCZ-RSS-TTY} & Process ID-Virtual Memory Size-Residence Memory Size-Console Process running on \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
ps aux | grep sshd & Find SSHD service running on system \tn 
% Row Count 6 (+ 2)
% Row 2
\SetRowColor{LightBackground}
ps -ef | less (PPID) & Parent Process ID \tn 
% Row Count 8 (+ 2)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{ps -e -o pid,args -{}-forest} \tn 
% Row Count 9 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.23965 cm} x{2.73735 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Process Properties w/ ps}}  \tn
% Row 0
\SetRowColor{LightBackground}
PID-VCZ-RSS-TTY & Process ID-Virtual Memory Size-Residence Memory Size-Console Process running on \tn 
% Row Count 4 (+ 4)
% Row 1
\SetRowColor{white}
ps aux | grep sshd & Find SSHD service running on system \tn 
% Row Count 6 (+ 2)
% Row 2
\SetRowColor{LightBackground}
ps -ef | less (PPID) & Parent Process ID \tn 
% Row Count 8 (+ 2)
% Row 3
\SetRowColor{white}
ps -e -o pid,args -{}-forest | less & Show relation between parent and child processes \tn 
% Row Count 11 (+ 3)
% Row 4
\SetRowColor{LightBackground}
ps aux -{}-sort pmem & Sorting process memory \tn 
% Row Count 12 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Systemd}}  \tn
% Row 0
\SetRowColor{LightBackground}
/usr/lib/systemd & Main config dir \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
systemctl -t help & List available unit types \tn 
% Row Count 3 (+ 2)
% Row 2
\SetRowColor{LightBackground}
ls \seqsplit{/usr/lib/systemd/system/*socket} & List available socket service \tn 
% Row Count 5 (+ 2)
% Row 3
\SetRowColor{white}
Socket: ListenStream=22 & Listen on TCP port 22 \tn 
% Row Count 7 (+ 2)
% Row 4
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{Service can be dead and socket can still listening, reducing resource to run service} \tn 
% Row Count 9 (+ 2)
% Row 5
\SetRowColor{white}
systemctl show sshd = man systemd.directives & List all options can be included in service \tn 
% Row Count 12 (+ 3)
% Row 6
\SetRowColor{LightBackground}
systemctl set-property httpd.service MemoryLimit=500m & Modify unit file htttpd \tn 
% Row Count 15 (+ 3)
% Row 7
\SetRowColor{white}
Target & Group of unit file \tn 
% Row Count 16 (+ 1)
% Row 8
\SetRowColor{LightBackground}
systemctl get-default & Default targart \tn 
% Row Count 18 (+ 2)
% Row 9
\SetRowColor{white}
systemctl set-default multi-user.target & Set default to multi.user \tn 
% Row Count 20 (+ 2)
% Row 10
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{When boot \seqsplit{systemd.unit=rescue.target}} \tn 
% Row Count 21 (+ 1)
% Row 11
\SetRowColor{white}
systemctl list-units & List all current units \tn 
% Row Count 23 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.14011 cm} x{2.83689 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Linux Log}}  \tn
% Row 0
\SetRowColor{LightBackground}
Make dir "journal" in /var/log & make journal consistently \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
vim \seqsplit{/etc/systemd/journald}.conf & change storage=auto to make journalctl consistently \tn 
% Row Count 5 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.73735 cm} x{2.23965 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Managing Shell Jobs}}  \tn
% Row 0
\SetRowColor{LightBackground}
sleep 600 then Ctrl+Z  or sleep 600 \& & Start job in background \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
fg & Move last bg job to foreground \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
jobs & Show current jobs \tn 
% Row Count 5 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Cron jobs}}  \tn
% Row 0
\SetRowColor{LightBackground}
/etc/cron.d/ & Main dir to put file for scheduling (used by rpm) \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
minute hour dayofmonth month dayofweek username command & Crontab syntax \tn 
% Row Count 6 (+ 3)
% Row 2
\SetRowColor{LightBackground}
crontab -e & Open crontab for current user \tn 
% Row Count 8 (+ 2)
% Row 3
\SetRowColor{white}
{\emph{/10 }} {\emph{ }} 1-5 /bin/logger & Run logger every 10 minute on weekdays \tn 
% Row Count 10 (+ 2)
% Row 4
\SetRowColor{LightBackground}
cat /var/log/cron | grep CRON & Verify schedule cron jobs \tn 
% Row Count 12 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.94103 cm} x{3.03597 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Libraries, RPM}}  \tn
% Row 0
\SetRowColor{LightBackground}
ldd \seqsplit{/usr/bin/passwd} & Show all libraries the command need \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
rpm -qa | grep httpd & List all installed packages (query all) and see if httpd is installed \tn 
% Row Count 5 (+ 3)
% Row 2
\SetRowColor{LightBackground}
rpm -qi httpd & Provide info about package \tn 
% Row Count 7 (+ 2)
% Row 3
\SetRowColor{white}
rpm -ql http & Provide list of files installed from package \tn 
% Row Count 9 (+ 2)
% Row 4
\SetRowColor{LightBackground}
rpm -qc httpd & List configuration file (c) \tn 
% Row Count 11 (+ 2)
% Row 5
\SetRowColor{white}
rpm -qd httpd & List documentation about package (d) \tn 
% Row Count 13 (+ 2)
% Row 6
\SetRowColor{LightBackground}
rpm -qpi filename & Provide info about uninstalled package \tn 
% Row Count 15 (+ 2)
% Row 7
\SetRowColor{white}
rpm -qp -{}-scripts filename & Find which scripts are executed if package is installed \tn 
% Row Count 18 (+ 3)
% Row 8
\SetRowColor{LightBackground}
rpm -qf /etc/nanorc & Find out which package the file coming from \tn 
% Row Count 20 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.43873 cm} x{2.53827 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Configuring GRUB2 Boot Loader}}  \tn
% Row 0
\SetRowColor{LightBackground}
Press ESC after boot & Stop booting process \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
Rescue kernel & Boot w/ minimal modules \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
Press e & Edit \tn 
% Row Count 5 (+ 1)
% Row 3
\SetRowColor{white}
Take out "rhgb" "quiet" & See what's happen upon boot \tn 
% Row Count 7 (+ 2)
% Row 4
\SetRowColor{LightBackground}
Edit /etc/default/grub & Permanent boot modifications \tn 
% Row Count 9 (+ 2)
% Row 5
\SetRowColor{white}
\seqsplit{/boot/grub2/grub.cfg} & Determine everything when system boot \tn 
% Row Count 11 (+ 2)
% Row 6
\SetRowColor{LightBackground}
grub2-mkconfig -o \seqsplit{/boot/grub2/grub.cfq} & Write a new GRUB config \tn 
% Row Count 13 (+ 2)
% Row 7
\SetRowColor{white}
\seqsplit{systemd.unit=rescue.target} & Start booting at rescue mode \tn 
% Row Count 15 (+ 2)
% Row 8
\SetRowColor{LightBackground}
\seqsplit{systemd.unit=emergency.target} & Boot at minimal \tn 
% Row Count 17 (+ 2)
% Row 9
\SetRowColor{white}
mount -o remount,rw / & Put root file system in read,write mode \tn 
% Row Count 19 (+ 2)
% Row 10
\SetRowColor{LightBackground}
rd.break & Break in boot procedure at the end of init params \tn 
% Row Count 22 (+ 3)
% Row 11
\SetRowColor{white}
chroot /sysroot & Set root file system to /sysroot \tn 
% Row Count 24 (+ 2)
% Row 12
\SetRowColor{LightBackground}
echo b \textgreater{}  \seqsplit{/proc/sysrq-trigger} & Crash and reset \tn 
% Row Count 26 (+ 2)
% Row 13
\SetRowColor{white}
touch .autorelabel & on CentOS \tn 
% Row Count 27 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.23965 cm} x{2.73735 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Rsyslog}}  \tn
% Row 0
\SetRowColor{LightBackground}
systemctl status rsyslog & Check status of Rsyslog \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{vim /etc/rsyslog.conf} \tn 
% Row Count 3 (+ 1)
% Row 2
\SetRowColor{LightBackground}
facility & authpriv, kern, mail \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
priority & .emerg, .crit, .debug \tn 
% Row Count 5 (+ 1)
% Row 4
\SetRowColor{LightBackground}
kern.*  /dev/console & Log from kern with all priority written to /dev/console \tn 
% Row Count 8 (+ 3)
% Row 5
\SetRowColor{white}
mail.*  -/var/log/maillog & Written not in realtime (-) \tn 
% Row Count 10 (+ 2)
% Row 6
\SetRowColor{LightBackground}
{\emph{.emerg  :omusrmsg:}} & Every user will receive emergency messsage on console \tn 
% Row Count 13 (+ 3)
% Row 7
\SetRowColor{white}
*.crit /var/log/critical & Save message with critical priority or higher to /var/log/critical \tn 
% Row Count 16 (+ 3)
% Row 8
\SetRowColor{LightBackground}
logger -p crit Critical Situation & Write log with crit priority \tn 
% Row Count 18 (+ 2)
% Row 9
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{\seqsplit{/etc/cron.daily/logrotate}} \tn 
% Row Count 19 (+ 1)
% Row 10
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{logrotate.conf} \tn 
% Row Count 20 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.89126 cm} x{3.08574 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Install software}}  \tn
% Row 0
\SetRowColor{LightBackground}
tar xvf filename -C /tmp & Decompress tar file verbose (v), x (extract) f(file) to /tmp dir \tn 
% Row Count 3 (+ 3)
% Row 1
\SetRowColor{white}
file filename & Find info about compressed file \tn 
% Row Count 5 (+ 2)
% Row 2
\SetRowColor{LightBackground}
gunzip {\emph{filename}} & Decompress file \tn 
% Row Count 7 (+ 2)
% Row 3
\SetRowColor{white}
tar czvf etc.tar /etc/ & Create tarball (c) and compress (z) \tn 
% Row Count 9 (+ 2)
% Row 4
\SetRowColor{LightBackground}
gunzip {\emph{filename}} & Unzip file \tn 
% Row Count 11 (+ 2)
% Row 5
\SetRowColor{white}
-p & preserver permission while decompress, compress \tn 
% Row Count 13 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.64241 cm} x{3.33459 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Process Signals}}  \tn
% Row 0
\SetRowColor{LightBackground}
Within top, press k & PID, 15(sigterm) \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
kill 14053 & Kill process 14053 \tn 
% Row Count 3 (+ 1)
% Row 2
\SetRowColor{LightBackground}
killall dd & Kill all process w/name dd \tn 
% Row Count 4 (+ 1)
% Row 3
\SetRowColor{white}
kill -9 14321 & Kill process 14321 w/ signal 9 (kill) \tn 
% Row Count 6 (+ 2)
% Row 4
\SetRowColor{LightBackground}
kill \$(pidof dd) & Kill all dd process, similar to killall \tn 
% Row Count 8 (+ 2)
% Row 5
\SetRowColor{white}
kill -l & List of kill signal \tn 
% Row Count 9 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.14011 cm} x{2.83689 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{SELinux Booleans}}  \tn
% Row 0
\SetRowColor{LightBackground}
getsebool -a & List of all current booleans \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
setsebool \seqsplit{ftpd\_anon\_write} on & Switch on to anonymous writing on ftp \tn 
% Row Count 4 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{SELinux}}  \tn
% Row 0
\SetRowColor{LightBackground}
getenforece & Current mode of SELinux \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
setenforce Permissive & Change to Permissive mode \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
cd \seqsplit{/etc/sysconfig/selinux} & Disable or enable SELinux \tn 
% Row Count 6 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.53827 cm} x{2.43873 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Systemd timers, at}}  \tn
% Row 0
\SetRowColor{LightBackground}
\seqsplit{/usr/lib/systemd/system} & Dir for unit file and timers \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
systemctl status atd & Check at daemon status \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
at 11:00, Ctrl+d to start job & start job at 11 \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
atq & Current jobs running w/ at \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
atrm {\emph{jobnumber}} & Remove job \tn 
% Row Count 9 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{SELinux Labels}}  \tn
% Row 0
\SetRowColor{LightBackground}
man semanage-fcontext & man page for setting context \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
semanage fcontext -a -t \seqsplit{httpd\_sys\_content\_t} "/web(/.*)?" & Setting SELinux to allow Apache read from /web \tn 
% Row Count 5 (+ 3)
% Row 2
\SetRowColor{LightBackground}
\mymulticolumn{2}{x{5.377cm}}{ls -lZd /web} \tn 
% Row Count 6 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{restorecon -Rv /web} \tn 
% Row Count 7 (+ 1)
% Row 4
\SetRowColor{LightBackground}
semanage port -a -t http\_port\_t -p tcp 444 & Allow Apache listen to port 444 \tn 
% Row Count 10 (+ 3)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.58804 cm} x{2.38896 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{SEAlert}}  \tn
% Row 0
\SetRowColor{LightBackground}
less /var/log/messages & Look for sealert \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
sealrt -l {\emph{code}} & Troubleshoot sealert \tn 
% Row Count 4 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.4885 cm} x{2.4885 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Kernel Modules}}  \tn
% Row 0
\SetRowColor{LightBackground}
lsmod | less & List modules \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
modprobe cdrom & Load cdrom module \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
modinfo cdrom & Info about module \tn 
% Row Count 3 (+ 1)
% Row 3
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{/etc/modprobe.d} \tn 
% Row Count 4 (+ 1)
% Row 4
\SetRowColor{LightBackground}
echo options cdrom autoclose=1 \textgreater{} cdrom.conf & Create cdrom.conf to automatically apply option \tn 
% Row Count 7 (+ 3)
% Row 5
\SetRowColor{white}
/proc & Interface to modify linux kernel \tn 
% Row Count 9 (+ 2)
% Row 6
\SetRowColor{LightBackground}
echo 1 \textgreater{} \seqsplit{/proc/sys/ipv6/conf/all/disable\_ipv6} & Disable ipv6 on runtime \tn 
% Row Count 12 (+ 3)
% Row 7
\SetRowColor{white}
echo \seqsplit{net.ipv6.conf.all.disable\_ipv6} = 1 \textgreater{} \seqsplit{etc/sysctl.d/ipv6.conf} & Disable ipv6 persistently \tn 
% Row Count 16 (+ 4)
% Row 8
\SetRowColor{LightBackground}
sysctl -a & List all tools \tn 
% Row Count 17 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{1.89126 cm} x{3.08574 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Yum}}  \tn
% Row 0
\SetRowColor{LightBackground}
yum search {\emph{pacckage}} & Search for package \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
yum info {\emph{package}} & Info about package \tn 
% Row Count 4 (+ 2)
% Row 2
\SetRowColor{LightBackground}
yum provides */filename & Provide package info \tn 
% Row Count 6 (+ 2)
% Row 3
\SetRowColor{white}
yum remove {\emph{package}} & Remove package \tn 
% Row Count 8 (+ 2)
% Row 4
\SetRowColor{LightBackground}
yum downloader {\emph{package}} & Download the package to analyse \tn 
% Row Count 10 (+ 2)
% Row 5
\SetRowColor{white}
yum list & Get information about package \tn 
% Row Count 12 (+ 2)
% Row 6
\SetRowColor{LightBackground}
yum install & Install from the repo \tn 
% Row Count 13 (+ 1)
% Row 7
\SetRowColor{white}
yum update & Compare packages and update if suitable \tn 
% Row Count 15 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{2.43873 cm} x{2.53827 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Process Priority}}  \tn
% Row 0
\SetRowColor{LightBackground}
RT & Real time process, part of the kernel \tn 
% Row Count 2 (+ 2)
% Row 1
\SetRowColor{white}
\mymulticolumn{2}{x{5.377cm}}{Within top, press r} \tn 
% Row Count 3 (+ 1)
% Row 2
\SetRowColor{LightBackground}
nice -n 5 dd if/dev/zero of=/dev/null \& & Run dd command with nice value of 5 and priority of 25 \tn 
% Row Count 6 (+ 3)
% Row 3
\SetRowColor{white}
renice -n 5 14053 & Change priority of process id 14053 \tn 
% Row Count 8 (+ 2)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{x{0.89586 cm} x{4.08114 cm} }
\SetRowColor{DarkBackground}
\mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Changing top Display Properties}}  \tn
% Row 0
\SetRowColor{LightBackground}
Press f & Changing top window and sorting \tn 
% Row Count 1 (+ 1)
% Row 1
\SetRowColor{white}
Press z & Color top window \tn 
% Row Count 2 (+ 1)
% Row 2
\SetRowColor{LightBackground}
Press W & Write to config file \tn 
% Row Count 3 (+ 1)
\hhline{>{\arrayrulecolor{DarkBackground}}--}
\end{tabularx}
\par\addvspace{1.3em}

\begin{tabularx}{5.377cm}{X}
\SetRowColor{DarkBackground}
\mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Managing Processes}}  \tn
\SetRowColor{LightBackground}
\mymulticolumn{1}{p{5.377cm}}{\vspace{1px}\centerline{\includegraphics[width=5.1cm]{/web/www.cheatography.com/public/uploads/nhatlong0605_1537825032_Screenshot from 2018-09-25 09-36-46.png}}} \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\SetRowColor{LightBackground}
\mymulticolumn{1}{x{5.377cm}}{Load average: last min, last 5 mins, last 15 mins \newline Press 1 to see number of CPU cores \newline Zombie task: Tasks lost communication w/ parent process \newline CPU: US process started by users, SY process relay directly to hardware, ni (nice) process w/ adjusted priority, id (idle) CPU time, wa(waiting) for  harddisk. \newline S for status, R for running, S for sleeping \newline VIRT virtual mem, RES resident mem process really using, SHR sharing mem to share with other processes \newline top -u student: process started by user}  \tn 
\hhline{>{\arrayrulecolor{DarkBackground}}-}
\end{tabularx}
\par\addvspace{1.3em}


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

\end{document}