D-E

daemon: A process such as the Web service (httpd) or X Font Server (xfs) that runs in the background and executes as required.
/dev: The directory with device files, used to represent hardware and software components.
DHCP (Dynamic Host Configuration Protocol): DHCP clients lease IP addresses for a fixed period of time from a DHCP server on a local network. The BOOTP protocol allows DHCP clients to get IP address information from a remote DHCP server. The DHCP server daemon is dhcpd; the DHCP client daemon is dhclient.
Disk Druid: Anaconda's hard disk management program. While the functionality is similar to fdisk and parted, Disk Druid is easier to use. However, it is available only during the Linux installation process.
display manager: A Linux display manager includes a dialog box for your username and password. Two major display managers are used in RHEL: gdm (GNOME) and kdm (KDE).
dmesg: The dmesg command lists the kernel ring buffer and the initial boot messages. If your system successfully boots, /var/log/dmesg is one place to look for messages if you think you have boot problems.
DNS (Domain Name System): The DNS service maintains a database of fully qualified domain names such as www.redhat.com and IP addresses such as 206.132.41.202. If the domain name is not in the local database, DNS is normally configured to look to other, more authoritative, DNS servers. The associated daemon is named.
Dovecot: The Dovecot service is associated with POP and IMAP e-mail.
dual-core / multi-core: A dual-core CPU is one type of multiple-core CPU in which one physical integrated circuit includes two or more CPUs.
dumpe2fs: The dumpe2fs command provides a lot of information about the format of a partition.
e2label: The e2label command associates a device with a label, typically a filesystem directory.
edquota: The edquota command edits the quota for a user or a group.
emacs: The emacs editor is a popular text editor that can be run from a text console.
environment: Each user's environment specifies default settings such as login prompts, terminals, the PATH, mail directories, and more.
/etc/fstab: The/etc/fstab configuration file defines default mounted directories.
/etc/inittab: The /etc/inittab configuration file sets the default runlevel and starts key processes such as terminal gettys.
/etc/X11/prefdm: The /etc/X11/prefdm configuration file specifies the preferred GUI display manager.
exportfs: The exportfs command allows shared NFS directories to be shared with a network.
ExpressCard: An ExpressCard is the successor to the PC Card/PCMCIA standard. The two standards are not compatible, and PCMCIA cards do not fit into ExpressCard slots.