Changes between Red Hat Enterprise Linux 6 and 7

The distribution RHEL 7.x comes with a lot of changes on the administration side. Make sure you are aware of those and plan the migration of your infrastructure.

Paket manager Yum shifts to DNF

Yum is going to be deprecated and replaced by DNF.  It brings some significant changes:

• Faster, more mathematically correct method for solving dependency resolution
• A “clean”, well documented Python API with C bindings &
• Python 3 support

DNF or Dandified yum is the next generation version of yum. It roughly maintains CLI compatibility with yum and defines a strict API for extensions and plugins. Plugins can modify or extend features of DNF or provide additional CLI commands on top of those mentioned below. If you know the name of such a command (including commands mentioned bellow), you may find/install the package which provides it using the appropriate virtual provide in the form of dnf-command(<alias>) where <alias> is the name of the command; e.g. dnf-command(repoquery) for a repoquery command (the same applies to specifying dependencies of packages that require a particular command).

Isn’t this a Release by Another Name?

No, DNF marks a shift, and not just a fork to Python 3, C support and cleaner docs.  The move to libsolv, librepo and a slim, planned API means Yum’s organic sprawl and bespoke depsolving are being phased out.

The shift solves old depsolving problems and readies DNF for some of the changes afoot in the devops world — e.g. empowered and independent devops-ers who don’t want to reinvent the wheel on each deploy.  Whether that warrants more than a major release is a bike-shed argument.

System and command changes between RHEL 6 and RHEL 7

Between RHEL6 and RHEL7 there are a number of changes to tools, commands, and workflows. Changes that are likely to affect common administrative tasks are listed here:

• Anaconda RHEL installer completely redesigned
• Legacy GRUB boot loader replaced by GRUB2
• Procedure for bypassing root password prompt at boot completely different³
• SysV init system and all related tools replaced by systemd
• ext4 replaced by xfs as default filesystem type
• Directories /bin, /sbin, /lib and /lib64 are now all under the /usr directory
• Network interfaces have a new naming scheme based on physical device location (e.g., eth0 might become enp0s3)⁷
• ntpd replaced by chronyd as the default network time protocol daemon
• GNOME2 replaced by GNOME3 as default desktop environment
• System registration and subscription now handled exclusively with Red Hat Subscription Management (RHSM)
• MySQL replaced by Mariadb
• tgtd replaced by targetcli
• High Availability Add-On: RGManager removed as resource-management option (in favor of Pacemaker); all CMAN features merged into Corosync (qdiskd replaced by votequorum plugin); all tools unified into pcs
• ifconfig and route commands are further deprecated in favor of ip
• netstat further deprecated in favor of ss
• System user UID range extended from 0-499 to 0-999
• locate no longer available by default; (available as mlocate package)
• nc (netcat) replaced by nmap-ncat

Read more information on the support pages of RedHat