What Surprises Await When Installing CentOS 7? A Hands‑On Linux Ops Diary

Installation

When installing CentOS 7 the package selection is limited to a single group, the default partition scheme uses XFS instead of ext2/3/4, and the rest of the process is similar to previous RHEL‑based releases.

First Boot

After installation the boot menu shows a “rescue” entry; editing grub.conf reveals the kernel parameters. Adding “1” to the kernel line boots into single‑user (rescue) mode.

Switching to Console

The system boots to a graphical target; to obtain a text console the /etc/inittab file is essentially empty. Creating a symlink from /lib/systemd/system/runlevel3.target (or /etc/systemd/system/default.target) to the desired target switches to runlevel 3.

Network and Hostname Configuration

Network interfaces are renamed (e.g., enp1s5). The hostname must be set in /etc/hostname rather than the older /etc/sysconfig/network file.

Local YUM Repository and Mounting

After creating a local YUM repo, the CD must be mounted manually. Adding a mount command to /etc/rc.d/rc.local requires making the script executable with chmod +x rc.local, otherwise it will not run on boot.

LVM and XFS

LVM volumes on XFS can be created, but the resize2fs tool only works with ext* filesystems, leading to “superblock” errors when attempting to resize XFS partitions.

DHCP Service Management

DHCP daemons are no longer managed via /etc/init.d. The service unit resides in /usr/lib/systemd/system/dhcpd.service and must be controlled with systemctl.

iptables

The iptables binary is located in /sbin rather than under /etc/init.d.

Additional Observations

The /etc/sysctl.conf file is empty; kernel parameters such as IP forwarding must be set under /proc/sys/net.