TCP dump and NMAP

1, to detect whether the specified network segment FTP service host, do not do DNS reverse analysis

nmap -sS –n –p 21 2, to detect whether the specified server has a specific port services

nmap –n –p T:21-25,80,110,3389–sS

3, the use of TCP connection scan to detect the specified server, even if it […]

keytool commands

Public and private keys from a Java Key Store Step 1: Creating the “public-private” key-pair. keytool -genkey -alias client -validity 365 -keystore keystore.jks 

Step 2: Validate the “public-private” key pair. keytool -list -v -keystore keystore.jks

Step 3: Extract the “public key” from the “public-private” keytool -export -alias client -keystore keystore.jks -rfc -file public.cert

Step 4: […]

OpenSSL Commands

OpenSSL Commands

After you applied for a personal or a host certificate, you may need to export the bundle from your browser and convert them into a different format to be able to use them in tools like GSI-SSH in order to authenticate yourself to the grid, and also to be able to install your […]

Boot Partition Full ( CentOS 7 )

Boot Partition Full ( CentOS 7 )

root@RHEL7HARDEN:~# df -h

Filesystem            Size  Used Avail Use% Mounted on /dev/mapper/vg0-root   96G   15G   77G  16% / devtmpfs              3.8G     0  3.8G   0% /dev tmpfs                 3.8G  152K  3.8G   1% /dev/shm tmpfs                 3.8G  9.1M  3.8G   1% /run tmpfs                 3.8G     0  3.8G   0% /sys/fs/cgroup /dev/sda1             283M  270M     0 100% /boot /dev/mapper/vg0-home  577G  […]

Verify Package Integrity Using RPM

Verify Package Integrity Using RPM

The RPM package management system includes the ability to verify the integrity of installed packages by comparing the installed files with information about the files taken from the package metadata stored in the RPM database.

Although an attacker could corrupt the RPM database (analogous to attacking the AIDE database […]

Remount the /dev/shm Partition in Fedora/CentOS

Remount the /dev/shm Partition in Fedora/CentOS This is to assist with a CSF warning you may receive about /dev/shm being incorrectly mounted, simply run the following:

nano /etc/fstab

Replace this line:

tmpfs /dev/shm tmpfs defaults 0 0

With this one:

tmpfs /dev/shm tmpfs defaults,noexec,nosuid 0 0

Save & Exit nano, then remount using the following […]

Bloging on Open Source,Linux,BSD and Internet World What is /dev/shm and how to mount /dev/shm

What is /dev/shm and how to mount /dev/shm

Introduction: /dev/shm is nothing but implementation of traditional shared memory concept. It is an efficient means of passing data between programs. One program will create a memory portion, which other processes (if permitted) can access. This will result into speeding up things on Linux. shm / shmfs […]

mount s3 bucket in linux EC2 instance

if you have not created a s3 bucket kindly go through with EC2 documentation.The documentation is very clear and easy to understand .This is the link how to create S3bucket

After creating a new bucket follow the given below steps.

Step 1: Download the latest s3fs package from S3fs link

Step 2: Untar the […]

Increasing Linux server security with nodev, nosuid and no exec options

Expertise level: Advanced Hackers can use temporary storage directories such as /tmp to store and execute unwanted programs and hack into a server. Other temporary storage directories that can be used for malicious activities are /var/tmp and /dev/shm. Follow these steps to secure your Linux server against this vulnerability: Add nodev, nosuid, and noexec options to /tmp:

1. Edit the file /etc/fstab, enter: […]

Remove The GNOME GUI on RHEL 7 Centos 7 Fedora and Oracle Linux Server

[root@RHEL7HARDEN ~]# rpm -qa yum yum-3.4.3-132.el7.centos.0.1.noarch [root@RHEL7HARDEN ~]#


I captured the list of ‘Warning: group <groupname> does not exitst.’ (see previous post) from a ‘yum update’ run which I CTRL+c out of once the warnings ended. I removed the ‘Warning: group ‘ from the front and the ‘ does not exitst.’ from the back […]

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