Tag Archives: linux

How to Intrepret Shadow Passwords in UNIX

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.

How to Determine the Linux Distribution

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.

Shell Script: Calculate Yesterday’s Date on UNIX

shell script

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.

Recursive FTP from the Command Line

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.

UNIX Terminal Session Management

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.

How to Disable a CPU Core

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.

Mount ISO Image Under Linux

An ISO image is a disk image file of an optical disc. The format of the disc is defined by the International Organization for Standardization (ISO). ISO 9660 is the most commonly used optical disc file system. An ISO image can also contain UDF file system which is backwards compatible with ISO 9660.

Search for Files Bigger Than Certain Size

When the disk partition is filling up quickly, it’s quite an hassle for the system administrator to find out the location of the files taking up the most space.