Documentation Index
Fetch the complete documentation index at: https://docs.apinizer.com/llms.txt
Use this file to discover all available pages before exploring further.
Other
To check system time with “date” command and fix if it’s in wrong timezone
sudo ln -sf /usr/share/zoneinfo/Europe/Istanbul /etc/localtime
To manually set date if it’s in correct timezone but still wrong
date -s '2014-12-25 12:34:56'
If Ubuntu no-key error is received
# 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
To fix SSH working with dash instead of bash due to user definition
chsh -s /bin/bash $(whoami)
To see applications killed by OOM Killer
dmesg -T | egrep -i 'killed process'
Disk Checks
To See Current Usage and Limits on All Disks
To See Current Usage and Limits at a Specific Address
Memory Checks
To See Current Memory Amount and Limits
Processor Checks
To See Only Processor Count
cat /proc/cpuinfo | grep processor | wc -l
To See Total Thread Count
ps -eo nlwp | tail -n +2 | awk '{ num_threads += $1 } END { print num_threads }'
cat /proc/sys/kernel/threads-max
To See Total Thread Count Belonging to Java Application
ps -ef | grep java
# Java's id is written below, example: 10057
ps huH p 10057 | wc -l
Taking dump
# jcmd -> when under JRE
sudo -u apinizer ./jcmd 26032 Thread.print > ./Thread.dump
sudo -u apinizer ./jcmd 26032 GC.heap_dump ./Heap.dump
Determining Process Count for Current User
Jar Operations
jar -xf apinizer-gateway-2.1.2.jar
Creating Jar from File
jar -cf apinizer-gateway-2.1.2.jar **
Creating Jar from File with manifest File
/opt/apinizerManager/jre8162linux/bin/jar -cfm apinizer-gateway-2.1.2.jar ./META-INF/MANIFEST.MF **
File Operations
Transferring Folder to Another Server with SCP
scp -r /opt/apinizerManager/* <REMOTE_SERVER_USER>@<REMOTE_SERVER_ID>:<PATH_TO_COPY_TO>
To Convert tar.gz File to zip
tar xzf jre282linux.tar.gz && zip jre282linux.zip $(tar tf jre282linux.tar.gz)
To See Open Files
cat /etc/sysctl.conf
# system-wide maximum number of files
cat /proc/sys/fs/file-max
cat /proc/sys/fs/file-nr
To See Top Ten File Descriptors with Most Open Files
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
Processes with Most Open Files
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, $0; }
' | sort -k1n -u | tail -n42 | sed 's/^[0-9]* //'
Firewall Operations
sudo iptables -A PREROUTING -t nat -i ens160 -p tcp --dport 443 -j REDIRECT --to-port 9443
iptables-save > /opt/apinizerManager/iptables.conf
# The following is written into startManager
iptables-restore < /opt/apinizerManager/iptables.conf
max_allowed_packet=500M
lower_case_table_names=1
innodb_log_file_size=2G
Wget Operations
Downloading File from Google Drive with Wget
wget --load-cookies /tmp/cookies.txt "https://docs.google.com/uc?export=download&confirm=$(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
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
Network Operations
To See Process or Service Using a Specific Port
netstat -ltnp | grep -w ':80'
Running Ports
Example output:
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))
-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
Getting server certificate from Linux server
openssl s_client -showcerts -connect <URL>:443 </dev/null 2>/dev/null|openssl x509 -outform PEM > mycertfile.pem
Certificate import to jar file application
/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>
Vi Editor Operations
To write all commands related to Vi and vim, first press the escape key to enter command mode and most should start with : (colon) character.
To exit without saving edits
To exit by saving edits
Replace All
CURL Operations
Parameters:
-k: To go to SSL addresses without verification-v: For log-m 10: For timeout-u <USERNAME>: To send username and prompt for password--output response.txt: To save output
Sending SOAP request and logging response
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
Accessing Basic auth WSDL address (will ask for password) and saving it
curl -u username "http://api.address.com?wsdl" --output response.wsdl
