Boot options reference
This section contains information about some of the boot options that you can use to modify the default behavior of the installation program. For Kickstart and advanced boot options, see References section of the Performing an advanced installation document.
This section contains information about the various installation source boot options.
inst.repo=boot option specifies the installation source, that is, the location providing the package repositories and a valid
.treeinfofile that describes them. For example:
inst.repo=cdrom. The target of the
inst.repo=option must be one of the following installation media:
an installable tree, which is a directory structure containing the installation program images, packages, and repository data as well as a valid
a DVD (a physical disk present in the system DVD drive)
an ISO image of the full CentOS 8 installation DVD, placed on a hard drive or a network location accessible to the system.
You can use the
inst.repo=boot option to configure different installation methods using different formats. The following table contains details of the
inst.repo=boot option syntax:
Table 1. inst.repo= installation source boot options Source type Boot option format Source format
Installation DVD as a physical disk. 
Image file of the installation DVD, or an installation tree, which is a complete copy of the directories and files on the installation DVD.
Image file of the installation DVD. 
Installation tree, which is a complete copy of the directories and files on the installation DVD.
The NFS Server option uses NFS protocol version 3 by default. To use a different version, add
+nfsvers=Xto the option.
You can set disk device names with the following formats:
Kernel device name, for example
File system label, for example
File system UUID, for example
Non-alphanumeric characters must be represented as
\xNN, where NN is the hexadecimal representation of the character. For example,
\x20is a white space
inst.addrepo=boot option to add an additional repository that can be used as another installation source along with the main repository (
inst.repo=). You can use the
inst.addrepo=boot option multip le times during one boot. The following table contains details of the
inst.addrepo=boot option syntax.
REPO_NAMEis the name of the repository and is required in the installation process. These repositories are only used during the installation process; they are not installed on the installed system.
Table 2. inst.addrepo installation source boot options Installation source Boot option format Additional information
Installable tree at a URL
Looks for the installable tree at a given URL.
Installable tree at an NFS path
Looks for the installable tree at a given NFS path. A colon is required after the host. The installation program passes every thing after
nfs://directly to the mount command instead of parsing URLs according to RFC 2224.
Installable tree in the installation environment
Looks for the installable tree at the given location in the installation environment. To use this option, the repositor y must be mounted before the installation program attempts to load the available software groups. The benefit of this option is that you can have multiple repositories on one bootable ISO, and you can install both the main repository and additional repositories from the ISO. The path to the additional repositories is
/run/install/source/REPO_ISO_PATH. Additional, you can mount the repository directory in the
%presecti on in the Kickstart file. The path must be absolute and start with
/, for example
Mounts the given <device> partition and installs from the ISO that is specified by the <path>. If the <path> is not specified, the installation p rogram looks for a valid installation ISO on the <device>. This installation method requires an ISO with a valid installable tree.
noverifyssl=boot option prevents the installation program from verifying the SSL certificate for all HTTPS connections with the exception of the additional Kickstart repositories, where
--noverifysslcan be set per repository.
inst.stage2=boot option to specify the location of the installation program runtime image. This option expects a path to a directory containing a valid
.treeinfofile. The location of the runtime image is read from the
.treeinfofile. If the
.treeinfofile is not available, the installation program attempts to load the image from
inst.stage2option is not specified, the installation program attempts to use the location specified with
You should specify this option only for PXE boot. The installation DVD and Boot ISO already contain a correct
inst.stage2option to boot the installation program from themselves.
By default, the
inst.stage2=boot option is used on the installation media and is set to a specific label, for example,
inst.stage2=hd:LABEL=CentOS-8.0.1905-BaseOS-x86_64. If you modify the default label of the file system containing the runtime image, or if you use a customized procedure to boot the installation system, you must verify that the
inst.stage2=boot option is set to the correct value.
inst.stage2.allboot option is used to specify several HTTP, HTTPS, or FTP sources. You can use the
inst.stage2=boot option multiple times with the
inst.stage2.alloption to fetch the image from the sources sequentially until one succeeds. For example:
inst.stage2.all inst.stage2=http://hostname1/path_to_install_tree/ inst.stage2=http://hostname2/path_to_install_tree/ inst.stage2=http://hostname3/path_to_install_tree/
inst.dd=boot option is used to perform a driver update during the installation. See the Performing an advanced installation document for information on how to update drivers during installation.
When booting from a Binary DVD, the installation program prompts you to enter additional kernel parameters. To set the DVD as an installation source, append
inst.repo=hmcto the kernel parameters. The installation program then enables
HMCfile access, fetches the images for stage2 from the DVD, and provides access to the packages on the DVD for software selection. This option eliminates the requirement of an external network setup and expands the installation options.
inst.proxyboot option is used when performing an installation from a HTTP, HTTPS, FTP source. For example:
inst.nosaveboot option to control which installation logs and related files are not saved to the installed system, for example
all. Multiple values can be combined as a comma-separated list, for example:
inst.nosaveboot option is used for excluding files from the installed system that can’t be removed by a Kickstart %post script, such as logs and input/output Kickstart results.
Table 3. inst.nosave boot options Option Description
Disables the ability to save the input Kickstart results.
Disables the ability to save the output Kickstart results generated by the installation program.
Disables the ability to save the input and output Kickstart results.
Disables the ability to save all installation logs.
Disables the ability to save all Kickstart results, and all logs.
inst.multilibboot option to set DNF’s
multilib_policyto all, instead of best.
memcheckboot option performs a check to verify that the system has enough RAM to complete the installation. If there isn’t enough RAM, the installation process is stopped. The system check is approximate and memory usage during installation depends on the package selection, user interface, for example graphical or text, and other parameters.
nomemcheckboot option does not perform a check to verify if the system has enough RAM to complete the installation. Any attempt to perform the installation with less than the recommended minimum amount of memory is unsupported, and might result in the installation process failing.
This section contains information about commonly used network boot options.
Initial network initialization is handled by
ip=boot option to configure one or more network interfaces. To configure multiple interfaces, you can use the
ipoption multiple times, once for each interface; to do so, you must use the
rd.neednet=1option, and you must specify a primary boot interface using the
bootdevoption. Alternatively, you can use the
ipoption once, and then use Kickstart to set up further interfaces. This option accepts several different formats. The following tables contain information about the most common options.
In the following tables:
ipparameter specifies the client IP address. You can specify IPv6 addresses in square brackets, for example, [2001:DB8::1].
gatewayparameter is the default gateway. IPv6 addresses are also accepted.
netmaskparameter is the netmask to be used. This can be either a full netmask (for example, 255.255.255.0) or a prefix (for example, 64).
hostnameparameter is the host name of the client system. This parameter is optional.
Table 4. Network interface configuration boot option formats Configuration method Boot option format
Automatic configuration of any interface
Automatic configuration of a specific interface
Automatic configuration of a specific interface with an override
automatic configuration of a specific interface with an overridebrings up the interface using the specified method of automatic configuration, such as
dhcp, but overrides the automatically-obtained IP address, gateway, netmask, host name or other specified parameters. All parameters are optional, so specify only the parameters that you want to override.
methodparameter can be any of the following:
Table 5. Automatic interface configuration methods Automatic configuration method Value
IPv6 automatic configuration
iSCSI Boot Firmware Table (iBFT)
If you use a boot option that requires network access, such as
inst.ks=http://host:/path, without specifying the ip option, the installation program uses
To connect to an iSCSI target automatically, you must activate a network device for accessing the target. The recommended way to activate a network is to use the
nameserver=option specifies the address of the name server. You can use this option multiple times.
bootdev=option specifies the boot interface. This option is mandatory if you use more than one
ifname=options assigns an interface name to a network device with a given MAC address. You can use this option multiple times. The syntax is
ifname=interface:MAC. For example:
ifname=option is the only supported way to set custom network interface names during installation.
inst.dhcpclass=option specifies the DHCP vendor class identifier. The
dhcpdservice sees this value as
vendor-class-identifier. The default value is
inst.waitfornet=SECONDSboot option causes the installation system to wait for network connectivity before installation. The value given in the
SECONDSargument specifies the maximum amount of time to wait for network connectivity before timing out and continuing the installation process even if network connectivity is not present.
For more information about networking, see the Configuring and managing networking in RHEL 8 document.
This section contains information about configuring boot options for your console, monitor display, and keyboard.
console=option to specify a device that you want to use as the primary console. For example, to use a console on the first serial port, use
console=ttyS0. Use this option in conjunction with the
inst.textoption. You can use the
console=option multiple times. If you do, the boot message is displayed on all specified consoles, but only the last one is used by the installation program. For example, if you specify
console=ttyS0 console=ttyS1, the installation program uses
inst.lang=option to set the language that you want to use during the installation. The
locale -a | grep _or
localectl list-locales | grep _options return a list of locales.
inst.singlelangoption to install in single language mode, which results in no available interactive options for the installation language and language support configuration. If a language is specified using the
inst.langboot option or the
langKickstart command, then it is used. If no language is specified, the installation program defaults to
inst.geoloc=option to configure geolocation usage in the installation program. Geolocation is used to preset the language and time zone, and uses the following syntax:
valuecan be any of the following parameters:
Table 6. Values for the inst.geoloc boot option Value Boot option format
Use the Fedora GeoIP API
Use the Hostip.info GeoIP API
If you do not specify the
inst.geoloc=option, the installation program uses
inst.keymap=option to specify the keyboard layout that you want to use for the installation.
inst.cmdlineoption to force the installation program to run in command-line mode. This mode does not allow any interaction, and you must specify all options in a Kickstart file or on the command line.
inst.graphicaloption to force the installation program to run in graphical mode. This mode is the default.
inst.textoption to force the installation program to run in text mode instead of graphical mode.
inst.noninteractiveboot option to run the installation program in a non-interactive mode. User interaction is not permitted in the non-interactive mode, and
inst.noninteractivecan be used with a graphical or text installation. When the
inst.noninteractiveoption is used in text mode it behaves the same as the
inst.resolution=option to specify the screen resolution in graphical mode. The format is
NxM, where N is the screen width and M is the screen height (in pixels). The lowest supported resolution is 1024x768.
inst.vnc=option to run the graphical installation using VNC. You must use a VNC client application to interact with the installation program. When VNC sharing is enabled, multiple clients can connect. A system installed using VNC starts in text mode.
inst.vncpassword=option to set a password on the VNC server that is used by the installation program.
inst.vncconnect=option to connect to a listening VNC client at the given host location. For example
inst.vncconnect=<host>[:<port>]The default port is 5900. This option can be used with
inst.xdriver=option to specify the name of the X driver that you want to use both during installation and on the installed system.
inst.usefbxoption to prompt the installation program to use the frame buffer X driver instead of a hardware-specific driver. This option is equivalent to
modprobe.blacklist=option to blacklist or completely disable one or more drivers. Drivers (mods) that you disable using this option cannot load when the installation starts, and after the installation finishes, the installed system retains these settings. You can find a list of the blacklisted drivers in the
/etc/modprobe.d/directory. Use a comma-separated list to disable multiple drivers. For example:
inst.xtimeout=option to specify the timeout in seconds for starting X server.
inst.sshdoption to start the
sshdservice during installation, so that you can connect to the system during the installation using SSH, and monitor the installation progress. For more information about SSH, see the
ssh(1)man page. By default,
sshdis not started unless you use the
During installation, the root account has no password by default. You can set a root password during installation with the
inst.kdump_addon=option to enable or disable the Kdump configuration screen (add-on) in the installation program. This screen is enabled by default; use
inst.kdump_addon=offto disable it. Disabling the add-on disables the Kdump screens in both the graphical and text-based interface as well as the
%addon com_redhat_kdumpKickstart command.
This section contains information about the options that you can use when debugging issues.
inst.rescue=option to run the rescue environment. The option is useful for trying to diagnose and fix systems.
inst.updates=option to specify the location of the
updates.imgfile that you want to apply during installation. There are a number of sources for the updates.
Table 7. inst.updates= source updates Source Description Example
Updates from a network
The easiest way to use
inst.updates=is to specify the network location of
updates.img. This does not require any modification to the installation tree. To use this method, edit the kernel command line to include
Updates from a disk image
You can save an
updates.imgon a floppy drive or a USB key. This can be done only with an
ext2filesystem type of
updates.img. To save the contents of the image on your floppy drive, insert the floppy disc and run the command.
dd if=updates.img of=/dev/fd0 bs=72k count=20. To use a USB key or flash media, replace
/dev/fd0with the device name of your USB key.
Updates from an installation tree
If you are using a CD, hard drive, HTTP, or FTP install, you can save the
updates.imgin the installation tree so that all installations can detect the .img file. Save the file in the
images/directory. The file name must be
For NFS installs, there are two options: You can either save the image in the
images/directory, or in the
RHupdates/directory in the installation tree.
inst.loglevel=option to specify the minimum level of messages logged on a terminal. This concerns only terminal logging; log files always contain messages of all levels. Possible values for this option from the lowest to highest level are:
critical. The default value is
info, which means that by default, the logging terminal displays messages ranging from
When installation starts, the
inst.syslog=option sends log messages to the
syslogprocess on the specified host. The remote
syslogprocess must be configured to accept incoming connections.
inst.virtiolog=option to specify the virtio port (a character device at
/dev/virtio-ports/name) that you want to use for forwarding logs. The default value is
org.fedoraproject.anaconda.log.0; if this port is present, it is used.
inst.zramoption controls the usage of zRAM swap during installation. The option creates a compressed block device inside the system RAM and uses it for swap space instead of the hard drive. This allows the installation program to run with less available memory than is possible without compression, and it might also make the installation faster. By default, swap on zRAM is enabled on systems with 2 GiB or less RAM, and disabled on systems with more than 2 GiB of memory. You can use this option to change this behavior; on a system with more than 2 GiB RAM, use
inst.zram=1to enable the feature, and on systems with 2 GiB or less memory, use
inst.zram=0to disable the feature.
rd.live.ramoption is specified, the
stage 2image is copied into RAM. Using this option when the
stage 2image is on an NFS server increases the minimum required memory by the size of the image by roughly 500 MiB.
inst.nokilloption is a debugging option that prevents the installation program from rebooting when a fatal error occurs, or at the end of the installation process. Use the
inst.nokilloption to capture installation logs which would be lost upon reboot.
inst.noshelloption if you do not want a shell on terminal session 2 (tty2) during installation.
inst.notmuxoption if you do not want to use tmux during installation. The output is generated without terminal control characters and is meant for non-interactive uses.
You can use the
remotelogoption to send all of the logs to a remote
host:portusing a TCP connection. The connection is retired if there is no listener and the installation proceeds as normal.
inst.nodmraid=option to disable
Use this option with caution. If you have a disk that is incorrectly identified as part of a firmware RAID array, it might have some stale RAID metadata on it that must be removed using the appropriate tool, for example,
inst.nompath=option to disable support for multipath devices. This option can be used for systems on which a false-positive is encountered which incorrectly identifies a normal block device as a multipath device. There is no other reason to use this option.
Use this option with caution. You should not use this option with multipath hardware. Using this option to attempt to install to a single path of a multipath is not supported.
inst.gptboot option forces the installation program to install partition information to a GUID Partition Table (GPT) instead of a Master Boot Record (MBR). This option is not valid on UEFI-based systems, unless they are in BIOS compatibility mode. Normally, BIOS-based systems and UEFI-based systems in BIOS compatibility mode attempt to use the MBR schema for storing partitioning information, unless the disk is 232 sectors in size or larger. Disk sectors are typically 512 bytes in size, meaning that this is usually equivalent to 2 TiB. Using the
inst.gptboot option changes this behavior, allowing a GPT to be written to smaller disks.
This section contains information about deprecated boot options. These options are still accepted by the installation program but they are deprecated and are scheduled to be removed in a future release of CentOS.
methodoption is an alias for
repo=nfsiso:option is the same as
dns. Note that nameserver does not accept comma-separated lists; use multiple nameserver options instead.
- netmask, gateway, hostname
hostnameoptions are provided as part of the
BOOTIFoption is used automatically, so there is no requirement to use
Table 8. Values for the ksdevice boot option Value Information
Ignored as this option is the same as the default behavior
Ignored as this option is the default if
This section contains the boot options that have been removed from CentOS.
- askmethod, asknetwork
initramfsis completely non-interactive, so the
asknetworkoptions have been removed. Instead, use
inst.repoor specify the appropriate network options.
- blacklist, nofirewire
modprobeoption handles blacklisting kernel modules; use
modprobe.blacklist=<mod1>,<mod2>. You can blacklist the firewire module by using
headless=option specified that the system that is being installed to does not have any display hardware, and that the installation program is not required to look for any display hardware.
inst.decoratedoption was used to specify the graphical installation in a decorated window. By default, the window is not decorated, so it doesn’t have a title bar, resize controls, and so on. This option was no longer required.
- essid, wepkey, wpakey
Dracut does not support wireless networking.
This option was no longer required.
This option was removed as there are many options available for debugging dracut-based
dracut option rd.live.checkoption.
For a remote display of the UI, use the
This option was no longer required as the default TERM setting behaves as expected.
ipv6 is built into the kernel and cannot be removed by the installation program. You can disable ipv6 using
ipv6.disable=1. This setting is used by the installed system.
This option was no longer required as the installation program no longer handles upgrades.