Cherry-picking changes from #185

@zhujian0805 contributed some excellent cheatsheets in #185, but some
binary files seem to have gotten mixed into the commit as well. This
commit cherry-picks the cheatsheet file changes from that PR while
leaving behind the cruft.

Also performed minor editing on some of the cheatsheets.

cheat/cheatsheets/du

@@ -0,0 +1,2 @@
+# To sort directories/files by size
+du -sk *| sort -rn

cheat/cheatsheets/find

@@ -20,10 +20,10 @@ find ./path/ -name '*.txt' -exec rm '{}' \;
 find ./path/ -name '*.txt' | xargs grep 'string'
 
 # To find files with size bigger than 5 Mb and sort them by size:
-find ./ -size +5M -type f -print0 | xargs -0 ls -Ssh
+find . -size +5M -type f -print0 | xargs -0 ls -Ssh | sort -z
 
 # To find files bigger thank 2 MB and list them:
-find / -type f -size +20000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
+find . -type f -size +20000k -exec ls -lh {} \; | awk '{ print $9 ": " $5 }'
 
 # To find files modified more than 7 days ago and list file information
 find . -type f -mtime +7d -ls
@@ -41,4 +41,4 @@ find . -maxdepth 2 -name build -type d
 find . ! -iwholename '*.git*' -type f
 
 # Find all files that have the same node (hard link) as MY_FILE_HERE
-find / -type f -samefile MY_FILE_HERE 2>/dev/null
+find . -type f -samefile MY_FILE_HERE 2>/dev/null

cheat/cheatsheets/lvm

@@ -0,0 +1,7 @@
+#Exclusive Activation of a Volume Group in a Cluster 
+#Link --> https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/High_Availability_Add-On_Administration/s1-exclusiveactive-HAAA.html 
+1> vgs --noheadings -o vg_name
+2> volume_list = [ "rhel_root", "rhel_home" ]
+3> dracut -H -f /boot/initramfs-$(uname -r).img $(uname -r)
+4> Reboot the node
+5> uname -r to verify the correct initrd image

cheat/cheatsheets/nc

@@ -0,0 +1,20 @@
+# To open a TCP connection to port 42 of host.example.com, using port 31337 as the source port, with a timeout of 5 seconds:
+nc -p 31337 -w 5 host.example.com 42
+
+# To open a UDP connection to port 53 of host.example.com:
+nc -u host.example.com 53
+
+# To open a TCP connection to port 42 of host.example.com using 10.1.2.3 as the IP for the local end of the connection:
+nc -s 10.1.2.3 host.example.com 42
+
+# To create and listen on a UNIX-domain stream socket:
+nc -lU /var/tmp/dsocket
+
+# To connect to port 42 of host.example.com via an HTTP proxy at 10.2.3.4, port 8080. This example could also be used by ssh(1); see the ProxyCommand directive in ssh_config(5) for more information.
+nc -x10.2.3.4:8080 -Xconnect host.example.com 42
+
+# The same example again, this time enabling proxy authentication with username "ruser" if the proxy requires it:
+nc -x10.2.3.4:8080 -Xconnect -Pruser host.example.com 42
+
+# To choose the source IP for the testing using the -s option
+nc -zv -s source_IP target_IP Port

cheat/cheatsheets/route

@@ -1,5 +1,29 @@
-# Add a default gateway:
+# To display routing table IP addresses instead of host names:
+route -n
+
+# To add a default gateway:
 route add default gateway 192.168.0.1
 
-# Display routing table IP addresses instead of host names:
+# To add the normal loopback entry, using netmask 255.0.0.0 and associated with the "lo" device (assuming this device was previously set up correctly with ifconfig(8)).
-route -n
+route add -net 127.0.0.0 netmask 255.0.0.0 dev lo
+
+# To add a route to the local network 192.56.76.x via "eth0".  The word "dev" can be omitted here.
+route add -net 192.56.76.0 netmask 255.255.255.0 dev eth0
+
+# To delete the current default route, which is labeled "default" or 0.0.0.0 in the destination field of the current routing table.
+route del default
+
+# To add a default  route (which will be used if no other route matches).  All packets using this route will be gatewayed through "mango-gw". The device which will actually be used for that route depends on how we can reach "mango-gw" - the static route to "mango-gw" will have to be set up before.
+route add default gw mango-gw
+
+# To add the route to the "ipx4" host via the SLIP interface (assuming that "ipx4" is the SLIP host).
+route add ipx4 sl0
+
+# To add the net "192.57.66.x" to be gateway through the former route to the SLIP interface.
+route add -net 192.57.66.0 netmask 255.255.255.0 gw ipx4
+
+# To install a rejecting route for the private network "10.x.x.x."
+route add -net 10.0.0.0 netmask 255.0.0.0 reject
+
+# This is an obscure one documented so people know how to do it. This sets all of the class D (multicast) IP routes to go via "eth0". This is the correct normal configuration line with a multicasting kernel
+route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0

cheat/cheatsheets/rsync

@@ -1,6 +1,14 @@
-# copy files from remote to local, maintaining file propertires and sym-links (-a), zipping for faster transfer (-z), verbose (-v).  
+# To copy files from remote to local, maintaining file properties and sym-links (-a), zipping for faster transfer (-z), verbose (-v).  
 rsync -avz host:file1 :file1 /dest/
 rsync -avz /source host:/dest
 
-# Copy files using checksum (-c), rather than time, to detect if the file has changed. (Useful for validating backups). 
+# Copy files using checksum (-c) rather than time to detect if the file has changed. (Useful for validating backups). 
 rsync -avc /source/ /dest/
+
+# Copy contents of /src/foo to destination:
+
+# This command will create /dest/foo if it does not already exist
+rsync -auv /src/foo /dest
+
+# Explicitly copy /src/foo to /dest/foo
+rsync -auv /src/foo/ /dest/foo

cheat/cheatsheets/sed

@@ -10,5 +10,8 @@ echo 'It is daytime' | sed 's/day/night/g'
 # To remove leading spaces
 sed -i -r 's/^\s+//g' file.txt
 
-# Remove empty lines and print results to stdout:
+# To remove empty lines and print results to stdout:
 sed '/^$/d' file.txt
+
+# To replace newlines in multiple lines
+sed ':a;N;$!ba;s/\n//g'  file.txt

cheat/cheatsheets/snmpwalk

@@ -0,0 +1,5 @@
+# To retrieve all of the variables under system for host zeus
+snmpwalk -Os -c public -v 1 zeus system
+
+# To retrieve the scalar values, but omit the sysORTable for host zeus
+snmpwalk -Os -c public -v 1 -CE sysORTable zeus system