OS-ShadowSheet.sh

#Checking for the IP's Performing DDOS attack.
netstat -ntu|awk '{print $5}'| cut -d: -f1 -s | sort| uniq -c| sort -nk1 -r

#**********Compression and Decompression**********#

#For compressing to tar.gz file
tar czvf create.tar.gz /directory/to/be/compressed/

#For Extracting tar.gz file in specific directory
tar -xzvf yourfile.tar.gz -C /extracting/directory

#Compressing a direcrory in zip file
zip -r file.zip /directory/to/be/compressed

#Decompressing zip file in a directory
unzip file.zip -d /directory/to/be/extracted

#*************************************************#

#************************************File Transferring Methods************************************#

#For transferring files and folders through rsync
rsync -avzr source_username@source_ip:/source/directory/ /destinaton/path/ 

rsync -avzr /source/directory/  destination_username@destination_ip:/destination/directory/  

#Transferring file through rsync in case of any other port
rsync -avz -e "ssh -p $portNumber" user@remoteip:/path/to/files/ /destination/directory/

#For transferring files and folders through SCP (SSH)
scp -i private.key -P <portnumber> -r source_username@source_ip:/path/to/the/directory/ /destination/directory/

#For transferring files and folders through SFTP
sftp -r source_username@source_ip:/source/directory/filename.tar.gz /destination/directory/

#For transferring files and folders through FTP
wget -m --source-user=xxxxxxx --source-password=xxxxxxx ftp://X.X.X.X/source-path-to-file/

#*************************************************************************************************#

#***************Disk Space and Inodes***************#

#For checking Disk space
ncdu
du -sh * | grep G

#To shrink out every log files
truncate -s 1000 /var/log/**/*.log 

#To check inodes:
for i in ./*; do echo $i; find $i |wc -l; done

#For deleting inodes folder or folder with too many files
find . -maxdepth 1 -type f -name "folder_name" -delete

#Deleting file or folder if name starts with "-"
rm -rf -- "-foldername"

#***************************************************#

#*******************************Email/Postfix*******************************#

#For Sending email from server
"Message body" | mail -s "This is Subject" receipt@mail.com  -aFrom:sender@mail.com

#For clearing Mail queue
postsuper -d ALL

#Changing state of postfix
/etc/init.d/postfix status
/etc/init.d/postfix reload
/etc/init.d/postfix restart
/etc/init.d/postfix stop
/etc/init.d/postfix start

Hostname can be change from file "/etc/postfix/main.cf"
myhostname = fqdn.example.com

Email credentials are store in file "/etc/postfix/sasl_passwd"

#***************************************************************************#

#******************Useful Redis Commands******************#

#For checking directory path and dbfilename
CONFIG GET dir
CONFIG GET dbfilename

#For checking maxmemory (it shows in bytes)
config get maxmemory

#For setting maxmemory
config set maxmemory 1gb

#For changing maxmemory policy
config set maxmemory-policy allkeys-lru

'Link for LRU-Cache and'
https://redis.io/topics/lru-cache

#If Redis shows error:
"2 exception(s):
Exception #0 (CredisException): MISCONF Redis is configured to save RDB snapshots, but it is currently not able to persist on disk. 
Commands that may modify the data set are disabled, because this instance is configured to report errors during writes if RDB snapshotting fails (stop-writes-on-bgsave-error option). 
Please check the Redis logs for details about the RDB error."

Steps for the resolution:
1. Modify /etc/sysctl.conf and add:
   vm.overcommit_memory=1
2. redis-cli
3. config set stop-writes-on-bgsave-error no

#*********************************************************#

#***************Shorewall***************#

#For opening port in Shorewall:
vi /etc/shorewall/rules
ACCEPT          net     fw      tcp     <port-number>

#For Blacklisting IP's in Shorewall
vi /etc/shorewall/interfaces
net     eth0            detect          dhcp,tcpflags,routefilter,nosmurfs,logmartians,blacklist

vi /etc/shorewall/blacklist
'IP will be required to be added in next line'

#For checking shorewall rules
shorewall check

#***************************************#

#********************** Misc **********************#

#Changing Swap memory
(If we wish to increase for 7GB then count will be 7M)
dd if=/dev/zero of=/path/for/swapfile.img bs=1024 count=2M
mkswap /path/for/swapfile.img
vim /etc/fstab -C
/path/for/swapfile.img swap swap sw 0 0
swapon /path/for/swapfile.img

#Turnoff Swap Memory
swapoff /path/to/swapfile.img

#For killing processes with particular pattern
ps -aux | grep 'pattern_here' | grep -v grep | awk '{print $2}' | xargs -r kill -9

#Converting .ppk into .key format
puttygen my.ppk -O private-openssh -o my.key

#Find a string or regex from folders and files then print line number with the corresponding file name which contain regex
sed -n '/pattern/=' filename

#For checking bandwidth of the server
vnstat -d 
"-d argument will shows the bandwidth for the last 30 days"

#For Resizing the File System Manually so that the attach storage device can be expand among it
resize2fs <filesystemname>
"Where filesystemname will be like '/dev/sda1' or '/dev/sda2'"

#For tracking stealth/particular process
/proc/<processID>

#For listing of file link counts
lsof +L1

#For checking attribute of file
lsattr

"Where as i=immutable and a=append-only"

#For changing attributes:
chattr -/+i [filename]
chattr -/+a [filename]

#Add in sudoer file for Granting root privilege without password prompt
username ALL=(ALL) NOPASSWD:ALL

#For checking apache version
/usr/sbin/apache2 -v

#For changing Apache Log Format
/etc/apache2/apache2.conf

#For checking Apache modules
apache2ctl -t -D DUMP_MODULES

#For checking PHP Information and configuration
php -i 

#For Checking Varnish Hit or Miss request
varnishlog | grep 'X-Cache:\|ReqURL'

#**************************************************#