In modern UNIX and Linux systems, user passwords are encrypted and stored in the /etc/shadow file. On BSD systems, the passwords are kept in the /etc/master.passwd file. The encrypted password field in the file contains more than just the encrypted password, it contains additional information.

Linux is a very customisable UNIX like operating system. To date, there are more than a couple of dozen Linux distributions available, based on this Wikipedia list.

There are times when you will need to calculate yesterday’s date in a UNIX shell script to run some date sensitive cron jobs. There are currently no standard command line tools in UNIX to perform such date arithmetic.

If your organisation has password aging policy set for your UNIX servers, there is a possibility that the root account may also get locked out due to the existence of an expiry date set in the /etc/shadow file. Once the root account is locked, all jobs (cron, etc) that require root privileges may start to fail. To unlock the root account on a SUN SPARC machine, you will need to:

The Registry Editor, or regedit.exe, allows the import and export of Windows registry entry files from the command line. It’s usage though, could prove to be a bit restrictive from the command line. From Windows XP edition onwards, Microsoft has included another command line tool called REG, or reg.exe. This tool is able perform almost all the tasks as it’s GUI counterpart – regedit.exe.

The default command line ftp client in most UNIX distributions do not support recursive downloads, even though recursive downloads is a basic feature in most GUI based ftp clients. But if you do not have access to the X-Windows or GUI, there are alternative ways to achieve the same result from the command line.

Have you ever encountered the dreaded “Connection closed by foreign host” message when you were logged into a remote server via SSH and you were in the middle of some important task? You have most probably just lost your session and you will have to start your task all over again. Well, you can prevent this from happening by using the screen command available in most UNIX and Linux distributions.

Multi-core CPUs pack multiple processors into a single chip thus allowing multiple threads to run at once. Most of the time, this is a good thing. But at times, for example, when you need to run some legacy applications that are not compatible with multi-core processing, you may be required to disable the cores.

You can change the Windows Domain User Account Password from the Command Line using the net command. This is applicable to Windows NT line of operating systems – NT 4, Windows 2000, Windows XP Pro, Windows Vista and so on.

Split Tunneling is a networking concept which allows the user to access the corporate private network via the VPN link, and connect to the local LAN via the same or different interface. This service is usually facilitated through a program such as VPN client software application. One such application is the Juniper Network Connect.