Others

To correct the system time if it is in the wrong timezone, use the "date" commandLink to To correct the system time if it is in the wrong timezone, use the "date" command

sudo ln -sf /usr/share/zoneinfo/Europe/Istanbul /etc/localtime
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To manually adjust the date in the correct timezone if it is still incorrectLink to To manually adjust the date in the correct timezone if it is still incorrect

date -s '2014-12-25 12:34:56'
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In case of encountering the "no-key" error on UbuntuLink to In case of encountering the "no-key" error on Ubuntu

#W: GPG error: https://download.docker.com/linux/ubuntu focal InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 7EA0A9C3F273FCD8

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 7EA0A9C3F273FCD8
BASH


To fix the issue where the user is running dash instead of bash after SSH due to user configurationLink to To fix the issue where the user is running dash instead of bash after SSH due to user configuration

chsh -s /bin/bash $(whoami)
BASH


To view applications killed by the OOM KillerLink to To view applications killed by the OOM Killer

dmesg -T | egrep -i 'killed process'
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Disk Operations

Checking usage and limits about current disksLink to Checking usage and limits about current disks

df -h
BASH

Checking usage and limits on specific pathLink to Checking usage and limits on specific path

du -sh <FILE_PATH>
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Memory Operations

Memory detailsLink to Memory details

cat /proc/meminfo
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Current memory usage and limitsLink to Current memory usage and limits

free -g
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Processor Operations

Cpu detailsLink to Cpu details

less /proc/cpuinfo
lscpu
BASH

Checking Cpu core countLink to Checking Cpu core count

cat /proc/cpuinfo | grep processor | wc -l
BASH

Checking total Thread countLink to Checking total Thread count

ps -eo nlwp | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'
 
cat /proc/sys/kernel/threads-max
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Checking total Thread count of Java applicationLink to Checking total Thread count of Java application

ps -ef | grep java
#The process ID of Java is written below, for example: 10057.
ps huH p 10057 | wc -l
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Taking DumpLink to Taking Dump

//jcmd-> While under the JRE
sudo -u apinizer ./jcmd 26032 Thread.print > ./Thread.dump
sudo -u apinizer ./jcmd 26032 GC.heap_dump ./Heap.dump
BASH

Setting Process count limit for current userLink to Setting Process count limit for current user

ulimit -Su 30000
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Jar Operations

Extracting from jarLink to Extracting from jar

jar -xf apinizer-gateway-2.1.2.jar
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Compress as JarLink to Compress as Jar

jar -cf apinizer-gateway-2.1.2.jar **
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Compressing file with manifes file as jarLink to Compressing file with manifes file as jar

/opt/apinizerManager/jre8162linux/bin/jar -cfm apinizer-gateway-2.1.2.jar ./META-INF/MANIFEST.MF **
BASH

File Operations

Copy files and directories between two locations with SCPLink to Copy files and directories between two locations with SCP

scp -r /opt/apinizerManager/* <REMOTE_SERVER_USER>@<REMOTE_SERVER_ID>:<PATH_TO_COPY_TO>
BASH


Extract tar.gz and compress as zipLink to Extract tar.gz and compress as zip

tar xzf jre282linux.tar.gz && zip jre282linux.zip $(tar tf jre282linux.tar.gz)
BASH

List of open filesLink to List of open files

lsof | wc -l
BASH

See File settingsLink to See File settings

cat /etc/sysctl.conf
// system-wide maximum number of files 
cat /proc/sys/fs/file-max
cat /proc/sys/fs/file-nr
BASH

Check the biggest 10 files that are openedLink to Check the biggest 10 files that are opened

cd /proc
for pid in [0-9]*
do
    echo "PID = $pid with $(ls /proc/$pid/fd/ | wc -l) file descriptors"
done | sort -rn -k5 | head | while read -r _ _ pid _ fdcount _
do
  command=$(ps -o cmd -p "$pid" -hc)
  printf "pid = %5d with %4d fds: %s\n" "$pid" "$fdcount" "$command"
done
BASH

Checking the processes that holds the most files openLink to Checking the processes that holds the most files open

lsof -Fnst | awk '
    { field = substr($0,1,1); sub(/^./,""); }
    field == "p" { pid = $0; }
    field == "t" { if ($0 == "REG") size = 0; else next; }
    field == "s" { size = $0; }
    field == "n" && size != 0 { print size, $0; }
' | sort -k1n -u | tail -n42 | sed 's/^[0-9]* //'
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Firewall Operations

sudo iptables -A PREROUTING -t nat -i ens160 -p tcp --dport 443 -j REDIRECT --to-port 9443
iptables-save > /opt/apinizerManager/iptables.conf
BASH 
#The following is written inside the `startManager`.
iptables-restore < /opt/apinizerManager/iptables.conf
 
max_allowed_packet=500M
lower_case_table_names=1
innodb_log_file_size=2G
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Wget Operations

Downloading from Google Drive with WgetLink to Downloading from Google Drive with Wget

wget --load-cookies /tmp/cookies.txt "https://docs.google.com/uc?export=download&confirm=$(wget --quiet --save-cookies /tmp/cookies.txt --keep-session-cookies --no-check-certificate 'https://docs.google.com/uc?export=download&id=Adres_Unique_Idsi_yZ8JlXtWwdOQg_5h' -O- | sed -rn 's/.*confirm=([0-9A-Za-z_]+).*/\1\n/p')&id=Adres_Unique_Idsi_yZ8JlXtWwdOQg_5h" -O apinizer.zip && rm -rf /tmp/cookies.txt
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Sorting by File Size

sudo lsof
| grep REG
| grep -v "stat: No such file or directory"
| grep -v DEL
| awk '{if ($NF=="(deleted)") {x=3;y=1} else {x=2;y=0}; {print $(NF-x) "  " $(NF-y) } }' 
| sort -n -u 
| numfmt  --field=1 --to=iec
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Network Operations

Checking a user process or service of specific portLink to Checking a user process or service of specific port

netstat -ltnp | grep -w ':80'
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With the running port

ss -antp
 State         Recv-Q        Send-Q                Local Address:Port                  Peer Address:Port
 LISTEN        0             128                         0.0.0.0:22                         0.0.0.0:*            users:(("sshd",pid=734,fd=4))
 ESTAB         0             0                    173.249.11.199:22                    3.83.11.233:48610        users:(("sshd",pid=44179,fd=5),("sshd",pid=44178,fd=5))
 ESTAB         0             0                    173.249.11.199:22                  176.43.11.169:4400         users:(("sshd",pid=4714,fd=5),("sshd",pid=4712,fd=5))
 ESTAB         0             0                    173.249.11.199:22                  176.43.11.169:4488         users:(("sshd",pid=1182,fd=5),("sshd",pid=1161,fd=5))
 ESTAB         0             0                    173.249.11.199:22                  78.175.12.218:37538        users:(("sshd",pid=4391,fd=5),("sshd",pid=4370,fd=5))
 ESTAB         0             40                   173.249.11.199:22                  78.175.12.218:40141        users:(("sshd",pid=4369,fd=5),("sshd",pid=4367,fd=5))
 ESTAB         0             0                    173.249.11.199:22                 222.186.13.130:12376        users:(("sshd",pid=44169,fd=5),("sshd",pid=44168,fd=5))
 ESTAB         0             0                    173.249.11.199:22                 157.230.12.208:56782        users:(("sshd",pid=44177,fd=5),("sshd",pid=44176,fd=5))
 LISTEN        0             128                            [::]:22                            [::]:*            users:(("sshd",pid=734,fd=6))    -t : Show only TCP sockets on Linux
 
//Diğer sık kullanılan parametreler şu şekildedir:
    -t : Show only TCP sockets on Linux
    -u : Display only UDP sockets on Linux
    -l : Show listening sockets. For example, TCP port 22 is opened by SSHD server.
    -p : List process name that opened sockets
    -n : Don’t resolve service names i.e. don’t use DNS


Certificate Operations

Obtaining a server certificate through a Linux server.Link to Obtaining a server certificate through a Linux server.

openssl s_client -showcerts -connect <URL>:443 </dev/null 2>/dev/null|openssl x509 -outform PEM > mycertfile.pem
BASH


Importing a certificate into a JAR fileLink to Importing a certificate into a JAR file

/opt/apinizerManager/jre8282linux/jre/bin/keytool -import -trustcacerts -keystore /opt/apinizerManager/jre8282linux/jre/lib/security/cacerts -storepass changeit -alias <CERTIFICATE_ALIAS> -import -file <CERTIFICATE_FILE>
BASH


Vi Editor Operations

To list all commands related to Vi and Vim, you typically enter command-line mode by pressing the escape key, and many commands begin with the colon (:) character.

To exit without saving changesLink to To exit without saving changes

:q!
BASH


To exit and save changesLink to To exit and save changes

:wq
BASH

Change AllLink to Change All

:%s/old_word/new_word/g
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CURL Operations

#To access SSL-protected addresses without verification -k
#for verbose logging -v
#For timeout -m 10
#To send username and make it asks for password  -u <USERNAME>
#To getting output --output response.txt

Logging the response after making a SOAP requestLink to Logging the response after making a SOAP request

curl -D -  --header "Content-Type:text/xml;charset=UTF-8" --header "SOAPAction:XXX" -d '<SOAP_BODY_GOES_HERE>' https://api.adres/apigateway/relativepath >> response.txt
BASH

Accessing a WSDL address with Basic Auth (prompting for the password) and saving itLink to Accessing a WSDL address with Basic Auth (prompting for the password) and saving it

curl -u username "http://api.address.com?wsdl" --output response.wsdl
BASH