Which Linux Services Can You Safely Disable? A Practical Guide

Linux services (daemons) are crucial for every Linux user. Disabling unnecessary services can improve efficiency, but not all services should be turned off. After installing CentOS, many services start automatically, many of which are unknown, so this guide explains which services can be disabled and which cannot.

Before disabling Linux services, you need to understand a few concepts:

What are Linux services/daemons?

What are Linux runlevels?

Tools used to manage Linux services.

Introduction to Linux service management tools.

You can manage Linux services from the command line using chkonfig or ntsysv, or with a graphical interface using system-config-services. GNOME users can also manage services via System → Administration → Server Settings → Services. Generally, system‑level services should not be disabled.

The most essential service is sshd for remote SSH access, which should always be kept. The author also recommends disabling the default sendmail service on CentOS 5.2 if it is not needed.

Linux Service: NetworkManager, NetworkManagerDispatcher

NetworkManager automatically switches network connections. It is useful for laptops but can be disabled on most desktops; enable it only if you need DHCP handling.

Linux Service: acpid

ACPI handles power management (power button, battery monitoring, lid switch, brightness, suspend, etc.). It should be enabled on laptops; servers may not need it.

Linux Service: anacron, atd, cron

These are schedulers. Enable cron for long‑running machines; atd and anacron can usually be disabled on desktops, though some tasks (e.g., cleaning /tmp) may rely on anacron.

Linux Service: apmd

Older hardware may use apmd. If ACPI is supported, disable apmd as ACPI handles its functions.

Linux Service: autofs

Automatically mounts removable media (USB drives). Enable it if you frequently use removable storage.

Linux Service: avahi-daemon, avahi-dnsconfd

Implements the Zeroconf protocol for discovering devices on a network without DNS. Disable unless you need Zeroconf services.

Linux Service: bluetooth, hcid, hidd, sdpd, dund, pand

Provides Bluetooth support. Most users can disable these services unless they use Bluetooth devices.

Linux Service: capi

Only useful for ISDN devices; disable for most users.

Linux Service: cpuspeed

Dynamically adjusts CPU frequency to save power. Enable on laptops or CPUs that support SpeedStep/PowerNow; disable if you prefer a fixed frequency.

Linux Service: cups, cups-config-daemon

Handles printing via CUPS. Enable if you have a CUPS‑compatible printer.

Linux Service: dc_client, dc_server

Provides distributed cache (Distcache) for SSL/TLS servers, often used by Apache. Disable on most desktops.

Linux Service: dhcdbd

Manages DHCP via DBUS. Keep the default disabled state.

Linux Service: diskdump, netdump

Used for kernel crash dumps. Enable only when debugging kernel crashes.

Linux Service: dund

Related to Bluetooth; generally disable.

Linux Service: firstboot

Runs one‑time tasks after Fedora installation. Can be disabled.

Linux Service: gpm

Provides mouse support for text consoles. Disable if you never use a console mouse; the author enables it in runlevel 3 and disables in runlevel 5.

Linux Service: hplip, hpiod, hpssd

Supports HP printers. Enable if you have compatible HP hardware.

Linux Service: iptables

Standard Linux firewall. Strongly recommended to enable, especially when directly connected to the Internet.

Linux Service: ip6tables

IPv6 firewall. Most users can disable unless IPv6 is in use.

Linux Service: irda, irattach

Provides infrared communication. Disable for most users.

Linux Service: irqbalance

Balances interrupts on SMP systems. Disable on single‑CPU machines; may improve performance on multi‑CPU systems.

Linux Service: isdn

ISDN internet access. Disable unless you use ISDN.

Linux Service: kudzu

Hardware detection and configuration. Enable only when adding new hardware; otherwise can be disabled.

Linux Service: lm_sensors

Monitors motherboard sensors (temperature, fan speed). Useful for laptops; otherwise can be disabled.

Linux Service: mctrans

Required when SELinux is enabled. Enable on systems using SELinux.

Linux Service: mdmonitor

Monitors Software RAID or LVM. Not critical; can be disabled.

Linux Service: mdmpd

Monitors Multi‑Path devices. Disable unless using multipath storage.

Linux Service: messagebus

DBUS interprocess communication service. Important system service; strongly recommended to keep enabled.

Linux Service: netplugd

Monitors network interfaces and runs commands on state changes. Keep disabled by default.

Linux Service: netfs

Automatically mounts network shares (NFS, Samba). Enable if you need network file systems; otherwise disable.

Linux Service: nfs, nfslock

Standard Unix file sharing. Disable unless you share files via NFS.

Linux Service: ntpd

Synchronizes system time over the Internet. Enable if the machine has a constant network connection.

Linux Service: pcscd

Provides smart‑card support. Disable if no smart‑card reader is present.

Linux Service: portmap

Supports NFS and NIS. Disable unless those services are used.

Linux Service: readahead_early, readahead_later

Preloads applications into memory for faster startup. Enable if you want quicker program launches.

Linux Service: restorecond

Monitors and restores SELinux file contexts. Enable if SELinux is in use.

Linux Service: rpcgssd, rpcidmapd, rpcsvcgssd

Used for NFS v4. Disable unless NFS v4 is required.

Linux Service: sendmail

Mail Transfer Agent. Disable for typical desktop users who use webmail or external mail clients.

Linux Service: smartd

SMART disk monitoring. Recommended for servers and useful for desktops with SMART‑capable drives.

Linux Service: smb

Samba file sharing between Linux and Windows. Enable if Windows users need access to Linux files.

Linux Service: sshd

Provides remote SSH login. Strongly recommended to keep enabled; disabling removes essential remote access.

Linux Service: xinetd

Super‑server that launches services on demand (e.g., telnet). Enable if you need on‑demand services; otherwise keep disabled.

Original source: http://donex.blog.51cto.com/2005970/810480