###################################################
##
##   Handy Commands - reminders
##
###################################################

####  Favorite Find Commands

# what files did I change in the last 15 minutes?
find . -maxdepth 3 -mmin -15 -type f

# remove all Thumbs.db
find . -name Thumbs.db -exec rm {} \;

# remove all files with filename <filename> in /tmp or deeper that are 30 days old or older
find /tmp -name '<filename>' -mtime +30 -exec rm {} \;

# in a home directory find all files created or changed in last 2 days
# except for invisible files and directories which are likely to be 
# updated regularly by running processes and not by manual changes.
find .  -mtime -2 -type f  ! -name '.*’  -not -path "./.*/*"

###################################################

####  locate
locate <filename>

# to update the "locate" database:
updatedb

###################################################

####  RSYNC

# SYNTAX:
#    rsync <source> <destination>
#
# NEVER put a trailing slash on destination
# Without a trailing slash on source, "copy entire directory"
# the below command will result in /data/tmp/bar

rsync foo:/src/bar  /data/tmp

# Slash at end of source means copy directory CONTENTS (think of it as rsync foo:/src/bar/* /data/tmp/bar)
# So if you WANT "bar" at the destination, that directory must already exist
# and you need to put it in the destination path
rsync foo:/src/bar/  /data/tmp/bar

# While preserving all links, attributes, ownership
# copy recursively all files in foo:/src/bar to /data/tmp/bar
# Use "archive" mode to copy
rsync -av foo:/src/bar/  /data/tmp/bar

# the -z option compresses during the copy
rsync -avz /src/bar  foo:/data/tmp/bar

-H is used to preserve hard links
-P if transfer is interrupted, do not delete partially transferred files (default), instead keep them.
rsync -avHP  foo:/src/bar/  /data/tmp

# -c, if file already exists in destination, skip based on checksum, not mod-time & size
rsync -acvHP  <source> <target>
rsync -acvHPe ssh  <source> <target>

#use the -e option to specify a protocol or shell
rsync --exclude-file=install_excludes.txt -acvHPe ssh username@192.168.0.100:/root/install  /tmp

rsync -acv -e "ssh -l username" host::module /dest

# rsync for large files over network
rsync -azPve ssh  /home/giantfile.tar  username@remotehost.com:/home/username

# rsync for backups
# -t transfers new files and updates files.  If files on source and destination are same, no action.
# -r recursive
# -p preserve permissions
rsync -rpte ssh  /home/username/valuable/files   username@backuphost:/backup/repository

####  Troubleshooting and Maintanance

###############################################
####
####  Remember to install "sysstat" to get iostat, sar
####  start and enable the sysstat service
####
###############################################

# Determine the resource utilization of a host
#   (install sysstat for iostat, mpstat, and sar)
# averages of various system statistics since last boot.
vmstat
# recent history of I/O wait and idle time
sar
# statistics of CPU and I/O for devices, partitions, and NFS.
iostat
# statistics broken down by CPU
mpstat -P ALL
# partition size and fullness
df -Thx squashfs
# performance testing for monitoring the Linux kernel
perf
# measures socket performance - needs to run on 2 machines:  sender and receiver
qperf 
# information about cpu architecture
lscpu
# network performance on a host
netstat -s  
# current active connections to where and using which service
netstat -p
# showing active tcp connections
netstat -natup
# show open ports
lsof -i -P -n | grep LISTEN
# show open ports
netstat -tulpn | grep LISTEN
# using ss instead of netstat:
ss -tulwn
ss -tulpw
ss -tulw
ss -tunlp4
# FLAGS
#    -t - Show TCP ports.
#    -u - Show UDP ports.
#    -n - Do not try to resolve hostnames.
#    -l - Show only listening ports.
#    -p - Show the processes that are using a particular socket.
#    -4 - Show only IPv4 sockets.
#
#### NETCAT netcat !!!
# example use netcat to test udp port 123 on ntp server 192.168.1.5
nc 192.168.1.5 -u 123

# Network - see interfaces (and get interface names)
ip -br link show
# using output of above command to see the interface names
# bring up a link that is down
ip link set <interface name> up
# determine link health (am I dropping packets?)
ip -s link show <interface name>
# examine the configuration for network interface
ethtool <interface name>
# show connected server status
ip neighbor show

# show port 2100
lsof -i:2100

# find open ports
nmap -sTU -O <ip addr>

# a snapshot of the top command output
top -n 1 -b   

# measure streaming speed ("real" output shows IO)
time cat /usr/share/dict/words

# memory installed and used on a host
cat /proc/meminfo

# which processes are the memory hogs?
# (sorts ps aux on column number 4 which is memory)
ps aux | sort -nk +4 | tail

# list all PCI devices on your computer (and chipset info)
# Helpful for determining make, model manufacturer so that you can find
# the right drivers for your hardware.
lspci 

# list all shared library dependencies for a program
# Helpful for determining missing packages
ldd <filename>

# list all open files
# Helpful to run before reboots, before unmounting directories
lsof

# Even more helpful - alphabetical order, unique listings
lsof |awk '{ print $1 }' | sort | uniq

# list environmental variables
printenv

# Another way to display file perms than ls -la
stat -c %a (filename)

# PS  - Process Commands
# (sorts ps aux on column number 4 which is memory)
ps aux | sort -nk +4 | tail

Process tree:
ps -ejH
ps axjf
		  
Information on threads:
ps -eLf
ps axms
		  
Security information:
ps -eo euser,ruser,suser,fuser,f,comm,label
ps axZ
ps -eM

Every process running as root (real & effective ID) in user format:
ps -U root -u root u

Processes excluding the square bracket processes.
if /proc/<pid>/cmdline is an empty string.  Usually spawned by kernel.
ps aux |grep -v "]"     
(note the double quotes)

PROCESS STATE CODES
       D    uninterruptible sleep (usually IO)
       R    running or runnable (on run queue)
       S    interruptible sleep (waiting for an event to complete)
       T    stopped, either by a job control signal or because it is being traced.
       W    paging (not valid since the 2.6.xx kernel)
       Z    defunct ("zombie") process, terminated but not reaped by its parent.
       <    high-priority (not nice to other users)
       N    low-priority (nice to other users)
       L    has pages locked into memory (for real-time and custom IO)
       s    is a session leader
       I    is multi-threaded (using CLONE_THREAD, like NPTL pthreads do)
       +    is in the foreground process group.


# SElinux: final command after making fix in single user mode, before reboot:
touch /.autorelabel

###########  HARDWARE INFORMATION  ###############

ipmitool sdr
dmidecide | grep -A3 '^System Information'
dmidecode -t 1
dmidecode -t 3
dmidecode -t system
 
lshw -c system | head
lshw

# chipset
lspci 


####  Network Troubleshooting and Maintanance
# traceroutes and routes
mtr   (command line ping-plotter)
ping
mping
hping
telnet or BETTER:  netcat  aka ncat  aka nc
nmap
wireshark   aka tshark
tcpdump
tracepath
traceroute
tracert
route
netstat -r
arp  =  ip -r  <neighbor host>
# like ifconfig
ip a
# like arp or route
ip r
# like netstat
ss [-r]
# netcat ****
nc

# Network Manager Command Line tool - CentOS8
nmcli

# more network commands
ifconfig  =  ip -a

# dns query - get domain name from ip addr or vice versa
nslookup
dig

####  Working with Files

# capture standard out and standard error together in a file
{command} 2>&1 filename.txt

# perl - display the directories where modules are accessed
perl -e "print \"@INC\""

# Display date as yyyymmdd
date +%Y%m%d

# sort file by third column (delimited by ":").  Valuable for Password files
sort -n -t : -k 3 filename

# remove new line
tr -d '\n|\r'

# cut is similar to perl split when used with -d "delimiter"
cut -d' '

# https://unix.stackexchange.com/questions/183994/understanding-unix-permissions-and-file-types

# Display the chmod file permissions in octal
stat -c %a (filename)


################ diff ###################
diff file1  file2

diff -r directory1 directory2

diff -ur

# compare files side by side -y
# ignore space changes -b
diff -y -b file1 file2


##########################################
########                    ##############
########  Terminal Helpers  ##############
########                    ##############
##########################################
# to remove carat-H on terminals
stty erase <backspace>

# Ubuntu - change default editor
sudo update-alternatives --config editor

# SCREEN suspend a session so you can reattach to it later:
  screen
  # hot key
  Ctrl-a
  # detach
  hot key, then d
  # list available screens
  screen -list
  # reconnect
  screen -r <screen id>
  # terminate current session
  exit
# OR  TMUX
  tmux
  # easier to script, easier to pass session to someone else
  # to reconnect
  tmux attach
  # hot key
  Ctrl-b
  # detach
  hot key, then d
  # list available sessions
  tmux list-sessions
  # reconnect
  tmux attach-session
  tmux attach-session -t <target number of session>
  # terminate current session
  exit