» Linux Xtreme Delusions (Redux): A Legend In My Own Mind

Trying to determine how much memory is free on a Linux machine is not as straight forward as it is on Windows. While Windows attempts to keep as much memory free as possible, Linux trys to keep as much memory used as possible. Here is how to determine how much memory is actually free and in use on your Linux machine.

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SSH is great for secure remote access and if you happen to connect to multiple machines then you will need multiple keys, especially if you are doing a password-less connection. Here is how to keep all your certificates nice and tidy.

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When you are installing new applications to your Unix server it is almost always better to use some soft of package management tool. Compiling from source allows you to custom tailor the application to your hardware, but most applications do not provide a means for uninstalling.
Another issue with installing from sources is that you do not have a central repository to list all your installed applications. src2pkg is the best of both worlds, compile from source and install via the package management system.

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Sometimes you will need to create an account that does not ask for a password, this is usually done for network administration. Creating an account without a password is a severe security violation and opens your sever up to attack. To get around this, create an account with a very strong password and then use public key encryption for logging in. If a user attempts to log in, they will need to know the password. However, you can log in with out a password by using the encrypted keys. You can further increase your security by ONLY allowing a login with the encrypted keys, but that is for another post.

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An ISO file is a CD or DVD image file. In order to attach an ISO file to the local file system, you have to mount it with a loop device. A loop device is used to make a regular file look like a block device.
The mount command is used to mount the device to the local file system.

mount -o loop,unhide,ro -t iso9660  
mount -o loop,unhide,ro -t udf

The “-o” option specifies extra parameters

loop use a loop device
unhide show hidden files
ro mount filesystem as readonly

The “-t” option specifies the filessytem to mount.

iso9660 CD-ROM filesystem
udf DVD Filesystem

The source parameters is the ISO.file. The target is the mount stub where the ISO file will be attached to the local filesystem.

Anatomy of the Linux file system