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.
Installation source boot options
This section contains information about the various installation source boot options.
- inst.repo=
-
The
inst.repo=
boot option specifies the installation source, that is, the location providing the package repositories and a valid.treeinfo
file that describes them. For example:inst.repo=cdrom
. The target of theinst.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
.treeinfo
file -
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 theinst.repo=
boot option syntax:Table 1. inst.repo= installation source boot options Source type Boot option format Source format CD/DVD drive
inst.repo=cdrom[:device]
Installation DVD as a physical disk. [1]
Installable tree
inst.repo=hd:device:/path
Image file of the installation DVD, or an installation tree, which is a complete copy of the directories and files on the installation DVD.
NFS Server
inst.repo=nfs:[options:]server:/path
Image file of the installation DVD. [2]
HTTP Server
inst.repo=http://host/path
Installation tree, which is a complete copy of the directories and files on the installation DVD.
HTTPS Server
inst.repo=https://host/path
FTP Server
inst.repo=ftp://username:password@host/path
HMC
inst.repo=hmc
The NFS Server option uses NFS protocol version 3 by default. To use a different version, add
+nfsvers=X
to the option.You can set disk device names with the following formats:
-
Kernel device name, for example
/dev/sda1
orsdb2
-
File system label, for example
LABEL=Flash
orLABEL=CENTOS8
-
File system UUID, for example
UUID=8176c7bf-04ff-403a-a832-9557f94e61db
Non-alphanumeric characters must be represented as
\xNN
, where NN is the hexadecimal representation of the character. For example,\x20
is a white space(" ")
.
-
- inst.addrepo=
-
Use the
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 theinst.addrepo=
boot option multip le times during one boot. The following table contains details of theinst.addrepo=
boot option syntax.The
REPO_NAME
is 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
inst.addrepo=REPO_NAME,[http,https,ftp]://<host>/<path>
Looks for the installable tree at a given URL.
Installable tree at an NFS path
inst.addrepo=REPO_NAME,nfs://<server>:/<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
inst.addrepo=REPO_NAME,file://<path>
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%pre
secti on in the Kickstart file. The path must be absolute and start with/
, for exampleinst.addrepo=REPO_NAME,file:///<path>
Hard Drive
inst.addrepo=REPO_NAME,hd:<device>:<path>
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.
- inst.noverifyssl=
-
The
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--noverifyssl
can be set per repository. - inst.stage2=
-
Use the
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.treeinfo
file. The location of the runtime image is read from the.treeinfo
file. If the.treeinfo
file is not available, the installation program attempts to load the image fromLiveOS/squashfs.img
.When the
inst.stage2
option is not specified, the installation program attempts to use the location specified withinst.repo
option.You should specify this option only for PXE boot. The installation DVD and Boot ISO already contain a correct
inst.stage2
option 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-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 theinst.stage2=
boot option is set to the correct value. - inst.stage2.all
-
The
inst.stage2.all
boot option is used to specify several HTTP, HTTPS, or FTP sources. You can use theinst.stage2=
boot option multiple times with theinst.stage2.all
option 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=
-
The
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. - inst.repo=hmc
-
When booting from a DVD1, the installation program prompts you to enter additional kernel parameters. To set the DVD as an installation source, append
inst.repo=hmc
to the kernel parameters. The installation program then enablesSE
andHMC
file 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.proxy
-
The
inst.proxy
boot option is used when performing an installation from a HTTP, HTTPS, FTP source. For example:[PROTOCOL://][USERNAME[:PASSWORD]@]HOST[:PORT]
- inst.nosave
-
Use the
inst.nosave
boot option to control which installation logs and related files are not saved to the installed system, for exampleinput_ks
,output_ks
,all_ks
,logs
andall
. Multiple values can be combined as a comma-separated list, for example:input_ks,logs
.The
inst.nosave
boot 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 input_ks
Disables the ability to save the input Kickstart results.
output_ks
Disables the ability to save the output Kickstart results generated by the installation program.
all_ks
Disables the ability to save the input and output Kickstart results.
logs
Disables the ability to save all installation logs.
all
Disables the ability to save all Kickstart results, and all logs.
- inst.multilib
-
Use the
inst.multilib
boot option to set DNF’smultilib_policy
to all, instead of best. - memcheck
-
The
memcheck
boot 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. - nomemcheck
-
The
nomemcheck
boot 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.
Network boot options
This section contains information about commonly used network boot options.
Initial network initialization is handled by |
- ip=
-
Use the
ip=
boot option to configure one or more network interfaces. To configure multiple interfaces, you can use theip
option multiple times, once for each interface; to do so, you must use therd.neednet=1
option, and you must specify a primary boot interface using thebootdev
option. Alternatively, you can use theip
option 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:
-
The
ip
parameter specifies the client IP address. You can specify IPv6 addresses in square brackets, for example, [2001:DB8::1]. -
The
gateway
parameter is the default gateway. IPv6 addresses are also accepted. -
The
netmask
parameter 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). -
The
hostname
parameter 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
ip=method
Automatic configuration of a specific interface
ip=interface:method
Static configuration
ip=ip::gateway:netmask:hostname:interface:none
Automatic configuration of a specific interface with an override
ip=ip::gateway:netmask:hostname:interface:method:mtu
The method
automatic configuration of a specific interface with an override
brings up the interface using the specified method of automatic configuration, such asdhcp
, 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.The
method
parameter can be any of the following:Table 5. Automatic interface configuration methods Automatic configuration method Value DHCP
dhcp
IPv6 DHCP
dhcp6
IPv6 automatic configuration
auto6
iSCSI Boot Firmware Table (iBFT)
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 usesip=dhcp
. -
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
ip=ibft
boot option.
-
- nameserver=
-
The
nameserver=
option specifies the address of the name server. You can use this option multiple times. - bootdev=
-
The
bootdev=
option specifies the boot interface. This option is mandatory if you use more than oneip
option. - ifname=
-
The
ifname=
options assigns an interface name to a network device with a given MAC address. You can use this option multiple times. The syntax isifname=interface:MAC
. For example:ifname=eth0:01:23:45:67:89:ab
The
ifname=
option is the only supported way to set custom network interface names during installation. - inst.dhcpclass=
-
The
inst.dhcpclass=
option specifies the DHCP vendor class identifier. Thedhcpd
service sees this value asvendor-class-identifier
. The default value isanaconda-$(uname -srm)
. - inst.waitfornet=
-
Using the
inst.waitfornet=SECONDS
boot option causes the installation system to wait for network connectivity before installation. The value given in theSECONDS
argument 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.
Additional resources
-
For more information about networking, see the Configuring and managing networking in RHEL 8 document.
Console boot options
This section contains information about configuring boot options for your console, monitor display, and keyboard.
- console=
-
Use the
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, useconsole=ttyS0
. Use this option in conjunction with theinst.text
option. You can use theconsole=
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 specifyconsole=ttyS0 console=ttyS1
, the installation program usesttyS1
. - inst.lang=
-
Use the
inst.lang=
option to set the language that you want to use during the installation. Thelocale -a | grep _
orlocalectl list-locales | grep _
options return a list of locales. - inst.singlelang
-
Use the
inst.singlelang
option 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 theinst.lang
boot option or thelang
Kickstart command, then it is used. If no language is specified, the installation program defaults toen_US.UTF-8
. - inst.geoloc=
-
Use the
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:inst.geoloc=value
. Thevalue
can be any of the following parameters:Table 6. Values for the inst.geoloc boot option Value Boot option format Disable geolocation
inst.geoloc=0
Use the Fedora GeoIP API
inst.geoloc=provider_fedora_geoip
Use the Hostip.info GeoIP API
inst.geoloc=provider_hostip
If you do not specify the
inst.geoloc=
option, the installation program usesprovider_fedora_geoip
. - inst.keymap=
-
Use the
inst.keymap=
option to specify the keyboard layout that you want to use for the installation. - inst.cmdline
-
Use the
inst.cmdline
option 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.graphical
-
Use the
inst.graphical
option to force the installation program to run in graphical mode. This mode is the default. - inst.text
-
Use the
inst.text
option to force the installation program to run in text mode instead of graphical mode. - inst.noninteractive
-
Use the
inst.noninteractive
boot option to run the installation program in a non-interactive mode. User interaction is not permitted in the non-interactive mode, andinst.noninteractive
can be used with a graphical or text installation. When theinst.noninteractive
option is used in text mode it behaves the same as theinst.cmdline
option. - inst.resolution=
-
Use the
inst.resolution=
option to specify the screen resolution in graphical mode. The format isNxM
, where N is the screen width and M is the screen height (in pixels). The lowest supported resolution is 1024x768. - inst.vnc=
-
Use the
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=
-
Use the
inst.vncpassword=
option to set a password on the VNC server that is used by the installation program. - inst.vncconnect=
-
Use the
inst.vncconnect=
option to connect to a listening VNC client at the given host location. For exampleinst.vncconnect=<host>[:<port>]
The default port is 5900. This option can be used withvncviewer -listen
. - inst.xdriver=
-
Use the
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.usefbx=
-
Use the
inst.usefbx
option to prompt the installation program to use the frame buffer X driver instead of a hardware-specific driver. This option is equivalent toinst.xdriver=fbdev
. - modprobe.blacklist=
-
Use the
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:modprobe.blacklist=ahci,firewire_ohci
- inst.xtimeout=
-
Use the
inst.xtimeout=
option to specify the timeout in seconds for starting X server. - inst.sshd
-
Use the
inst.sshd
option to start thesshd
service 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 thessh(1)
man page. By default,sshd
is not started unless you use theinst.sshd
option.During installation, the root account has no password by default. You can set a root password during installation with the
sshpw
Kickstart command. - inst.kdump_addon=
-
Use 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; useinst.kdump_addon=off
to 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_kdump
Kickstart command.
Debug boot options
This section contains information about the options that you can use when debugging issues.
- inst.rescue=
-
Use the
inst.rescue=
option to run the rescue environment. The option is useful for trying to diagnose and fix systems. - inst.updates=
-
Use the
inst.updates=
option to specify the location of theupdates.img
file 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 ofupdates.img
. This does not require any modification to the installation tree. To use this method, edit the kernel command line to includeinst.updates
.inst.updates=http://some.website.com/path/to/updates.img
.Updates from a disk image
You can save an
updates.img
on a floppy drive or a USB key. This can be done only with anext2
filesystem type ofupdates.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/fd0
with 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.img
in the installation tree so that all installations can detect the .img file. Save the file in theimages/
directory. The file name must beupdates.img
.For NFS installs, there are two options: You can either save the image in the
images/
directory, or in theRHupdates/
directory in the installation tree. - inst.loglevel=
-
Use the
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:debug
,info
,warning
,error
andcritical
. The default value isinfo
, which means that by default, the logging terminal displays messages ranging frominfo
tocritical
. - inst.syslog=
-
When installation starts, the
inst.syslog=
option sends log messages to thesyslog
process on the specified host. The remotesyslog
process must be configured to accept incoming connections. - inst.virtiolog=
-
Use the
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 isorg.fedoraproject.anaconda.log.0
; if this port is present, it is used. - inst.zram
-
The
inst.zram
option 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, useinst.zram=1
to enable the feature, and on systems with 2 GiB or less memory, useinst.zram=0
to disable the feature. - rd.live.ram
-
If the
rd.live.ram
option is specified, thestage 2
image is copied into RAM. Using this option when thestage 2
image is on an NFS server increases the minimum required memory by the size of the image by roughly 500 MiB. - inst.nokill
-
The
inst.nokill
option 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 theinst.nokill
option to capture installation logs which would be lost upon reboot. - inst.noshell
-
Use
inst.noshell
option if you do not want a shell on terminal session 2 (tty2) during installation. - inst.notmux
-
Use
inst.notmux
option 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. - remotelog
-
You can use the
remotelog
option to send all of the logs to a remotehost:port
using a TCP connection. The connection is retired if there is no listener and the installation proceeds as normal.
Storage boot options
- inst.nodmraid=
-
Use the
inst.nodmraid=
option to disabledmraid
support.
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=
-
Use the
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.gpt
-
The
inst.gpt
boot 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 2^32 sectors in size or larger. Disk sectors are typically 512 bytes in size, meaning that this is usually equivalent to 2 TiB. Using theinst.gpt
boot option changes this behavior, allowing a GPT to be written to smaller disks.
Deprecated boot options
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.
- method
-
The
method
option is an alias forinst.repo
. - repo=nfsiso
-
The
repo=nfsiso:
option is the same asinst.repo=nfs:
. - dns
-
Use
nameserver
instead ofdns
. Note that nameserver does not accept comma-separated lists; use multiple nameserver options instead. - netmask, gateway, hostname
-
The
netmask
,gateway
, andhostname
options are provided as part of theip
option. - ip=bootif
-
A PXE-supplied
BOOTIF
option is used automatically, so there is no requirement to useip=bootif
. - ksdevice
-
Table 8. Values for the ksdevice boot option Value Information Not present
N/A
ksdevice=link
Ignored as this option is the same as the default behavior
ksdevice=bootif
Ignored as this option is the default if
BOOTIF=
is presentksdevice=ibft
Replaced with
ip=ibft
. Seeip
for detailsksdevice=<MAC>
Replaced with
BOOTIF=${MAC/:/-}
ksdevice=<DEV>
Replaced with
bootdev
Removed boot options
This section contains the boot options that have been removed from CentOS.
|
- askmethod, asknetwork
-
initramfs
is completely non-interactive, so theaskmethod
andasknetwork
options have been removed. Instead, useinst.repo
or specify the appropriate network options. - blacklist, nofirewire
-
The
modprobe
option handles blacklisting kernel modules; usemodprobe.blacklist=<mod1>,<mod2>
. You can blacklist the firewire module by usingmodprobe.blacklist=firewire_ohci
. - inst.headless=
-
The
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.decorated
-
The
inst.decorated
option 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. - serial
-
Use the
console=ttyS0
option. - updates
-
Use the
inst.updates
option. - essid, wepkey, wpakey
-
Dracut does not support wireless networking.
- ethtool
-
This option was no longer required.
- gdb
-
This option was removed as there are many options available for debugging dracut-based
initramfs
. - inst.mediacheck
-
Use the
dracut option rd.live.check
option. - ks=floppy
-
Use the
inst.ks=hd:<device>
option. - display
-
For a remote display of the UI, use the
inst.vnc
option. - utf8
-
This option was no longer required as the default TERM setting behaves as expected.
- noipv6
-
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. - upgradeany
-
This option was no longer required as the installation program no longer handles upgrades.