Operating Systems in Practice

Remote Access

Remote Connection and SSH

• The most popular SSH client on Linux is **OpenSSH program.
• The most popular SSH program on Windows is PuTTY.
• Another way to connect to a remote machine is VPN.
• On Linux, GUI remote connection can be established through programs like RealVNC.
• On MAC, remote GUI connections are possible via Microsoft RDP on Mac.

Remote Connection

Allows us to manage multiple machines from anywhere in the world.

Secure shell (SSH)

A protocol implemented by other programs to securely access one computer from another.

• We can authenticate via password in SSH.
• But more secure way is the use of SSH keys. An SSH key is a pair of two keys:
  • Private
  • Public

Virtual private network (VPN)

Allows you to connect to a private network, like your work network, over the Internet.

Remote Connections on Windows

• Microsoft has built Remote Desktop Protocol or RDP for GUI remote connections.
  • A client named Microsoft Terminal Services Client or mtsc.exe is used for remote RDP connections.

PuTTY

A free, open source software that you can use to make remote connections through several network protocols, including SSH.

To connect via PuTTY in a CLI:

  putty.exe -ssh username@ip_address <Port Number> # Port number is 22 by default for SSH connections

To enable remote connection on a pc go-to:

  MY PC > Properties > Remote Settings

Remote Connection File Transfer

Secure copy (SCP)

A command you can use on Linux to copy files between computers on a network.

To copy file from local computer to remote:

  scp <filepath> username@ip_address:location

Remote Connection File Transfer on Windows

• PuTTY comes with PuTTY Secure Copy Client or pscp.exe.

  pscp.exe <filepath> username@ip_address:location
  

• To transfer files via PuTTY is a little time-consuming, so Windows came up with the concept of ShareFolders.

  To share folders via CLI:

  net share <ShareName>=<drive>:<DirectoryPath> /grant:everyone,full
  

  To list currently shared folders on your computer:

  net share
  

Virtualization

Virtual Machines

• To manage virtual instances, we can use FOSS program Virtual Box.

Virtual Instance

A single virtual machine.

Logging

System Monitoring

Log

A log is a system diary of events happening on the system.

Logging

The act of creating log events.

The Windows Event Viewer

It stores all the events happening on a Windows computer.

Linux logs

• The logs on Linux are stored in /var/log directory.
• One log file that pretty much everything on the system is /var/log/syslog
• The utility logrotate is used for log cleanup by the system.
• Centralized logging is used for parsing multiple systems log files in a single place.

Working with Logs

The logs are written in a very standard way, so we don’t need to go through each and every bit of them to troubleshoot problems, all you need to do is look for specific things.

• Logs can be searched with keywords like, error.
• Name of the troublesome program.
• The troubleshooting technique is viewing logs in the real time, to find the out the specific errors causing the program to fail.

To see real-time logs on Linux:

  tail -f /var/log/syslog

Operating System Deployment

Imaging Software

• It is extremely cumbersome to install OSs on new machines via USB drive formatted with OS.
• In IT world, tools are used to format a machine with an image of another machine, which includes everything, from the OS to the settings.

  Operating Systems Deployment Methods

• Disk cloning tools are used to obtain an image of a computer OS and settings. Some tools are:
  • Clonezilla (FOSS)
  • Symantec Ghost (Commercial)
• Different disk cloning tools offer different methods to clone systems
  • Disk-to-disk cloning

  Let’s use Linux CLI tool dd to copy files from a disk to make a clone.

  To copy from a USB drive, first unmount it:

  sudo umount /dev/sdX
  

  Then run dd:

  sudo dd if=/dev/sdX of=~/Desktop/my_usb_image.img bs=100M
  

Mobile Device Resetting and Imaging

• Factory resetting a device clean all user data and apps, and return the device to its original factory condition.
  • Watch out for expansion storage, like SD cards, as factory reset may format them too.
  • You will require primary account credentials to factory reset, this prevents misuse of stolen devices.
    • Re-flash a factory software can be done through computer.