100 Linux Tips and Tricks

Tip 20: Default file permissions

When you create a file, the system gives it default permissions. On most systems the permissions are 755 (read, write and execute for the owner, and read and execute for others).

This default is setup with the umask command. To use the command, you need to find the right octal number to give it. The permissions in the umask are turned off from 666. This means that a umask of 022 will give you the default of 755. To change your default permissions from 755 to 700, you would use this command:

umask 077

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100 Linux Tips and Tricks

Tip 21: Default boot mode

When a Linux system boots, it loads the kernel, all its drivers, and the networking servers, then the system will display a text login prompt. There, users can enter their user names and their passwords. But it doesn't have to boot this way.

There are 3 modes defined in most Linux distributions that can be used for booting. They are defined in /etc/inittab and have specific numbers. The first mode, also called runlevel 1, is single user mode. That mode will only boot the system for 1 user, with no networking. Runlevel 3 is the default mode. It will load the networking servers and display a text login prompt. Runlevel 5 is the graphical mode. If you have X Window installed and configured, you can use it to display a graphical login prompt.

The way to change this is to edit /etc/inittab and change the initdefault line:

id:3:initdefault:

Changing a 3 to a 5 will make the system display a xdm graphical screen on bootup.

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100 Linux Tips and Tricks

Tip 22: More information from usenet

There are newsgroups about everything. Newsgroups on the latest TV show, on gardening, and more. There also are newsgroups on Linux. In fact, the best help can be obtained from newsgroups. But which ones?

Here is a list of a few newsgroups dedicated to Linux, and what they are used for:

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Make sure you read the FAQ and rules of every newsgroup you want to post to.

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100 Linux Tips and Tricks

Tip 23: Bytes per inodes

When you format a partition using Linux's primary file system, ext2, you have the choice of how many bytes per inode you want. From the man page:

-i bytes-per-inode

Specify the bytes/inode ratio. mke2fs creates an inode for every bytes-per-inode bytes of space on the disk. This value defaults to 4096 bytes. bytes-per-inode must be at least 1024.

This means that by using a smaller size, you will save disk space but may slow down the system. It is a space/speed trade off.

This is similar to one of FAT16/FAT32' major differences.

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