You can add an SSH key to a Linux cloud image in a qcow2 format using the virt-sysprep utility. Here are the steps: Boot the cloud image in a virtual machine. Install the virt-sysprep utility: # apt-get update # apt-get install libguestfs-tools Copy your SSH public key to the virtual machine: $ ssh-copy-id user@virtual-machine Run … Read more

You can exclude files when using the scp command recursively by using the –exclude option of the rsync utility, which is used by scp to transfer files and directories. For example, to exclude files with the .log extension while copying all files and directories from the local directory /path/to/source to the remote directory /path/to/destination:   … Read more

To check the running processes on a Linux system, you can use the ps command. Here’s an example:   $ ps aux This command will show a list of all the running processes and their status information. The output includes the following columns: USER: the username of the owner of the process. PID: the process … Read more

The password file /etc/passwd contains one line for each user account. The passwd files are the local source of password information. To check the list of users on a Unix-like system, you can use the cut and /etc/passwd command as follows:   $ cut -d: -f1 /etc/passwd The /etc/passwd file contains information about each user on the … Read more

The curl command is a tool to download or transfer files/data from or to a server using FTP, HTTP, HTTPS, SCP, SFTP, SMB, and other supported protocols on FreeBSD, Linux, or Unix-like system. You can install curl on FreeBSD using the pkg command as follows: # pkg install curl This will download and install the latest version … Read more

You can turn off color in a Linux terminal/bash session by setting the environment variable TERM to dumb. You can do this by running the following command in your terminal: export TERM=dumb This will disable color output in the terminal until the terminal is closed or the environment variable is reset. To make the change … Read more

To patch the Meltdown CPU vulnerability (CVE-2017-5754) on a Linux system, you need to install the latest security updates and patches from your Linux distribution vendor. The exact steps to do this will depend on the distribution and version you’re using, but some common methods include using the package manager (e.g. yum, apt-get, dnf, zypper, … Read more

The Spectre vulnerability (CVE-2017-5753 and CVE-2017-5715) is a hardware-based vulnerability that affects modern microprocessors and can be exploited by attackers to access sensitive information, such as passwords and encryption keys. To patch the Spectre vulnerability on Linux, you will need to install the latest microcode update from your processor vendor and update your operating system. … Read more

You can find the path where a package is installed to on a CentOS/RHEL system using the yum provides command. For example, to find the path for the package httpd, you can run the following command: yum provides ‘*/httpd’ The output will list the packages that provide the specified file, including the full path to … Read more

To change the hostname of a FreeBSD system without rebooting, you can use the hostname command. To set the hostname to “new-hostname”, you can run the following command: hostname new-hostname To make the change permanent, you will need to edit the /etc/rc.conf file and modify the hostname variable. For example: vi /etc/rc.conf # Change the … Read more