1 .. _kernelparameters:
2
3 The kernel's command-line parameters
4 ====================================
5
6 The following is a consolidated list of the ke
7 by the __setup(), early_param(), core_param()
8 and sorted into English Dictionary order (defi
9 punctuation and sorting digits before letters
10 manner), and with descriptions where known.
11
12 The kernel parses parameters from the kernel c
13 if it doesn't recognize a parameter and it doe
14 parameter gets passed to init: parameters with
15 environment, others are passed as command line
16 Everything after "``--``" is passed as an argu
17
18 Module parameters can be specified in two ways
19 line with a module name prefix, or via modprob
20
21 (kernel command line) usbcore.blinkenl
22 (modprobe command line) modprobe usbco
23
24 Parameters for modules which are built into th
25 specified on the kernel command line. modprob
26 kernel command line (/proc/cmdline) and collec
27 when it loads a module, so the kernel command
28 loadable modules too.
29
30 Hyphens (dashes) and underscores are equivalen
31
32 log_buf_len=1M print-fatal-signals=1
33
34 can also be entered as::
35
36 log-buf-len=1M print_fatal_signals=1
37
38 Double-quotes can be used to protect spaces in
39
40 param="spaces in here"
41
42 cpu lists:
43 ----------
44
45 Some kernel parameters take a list of CPUs as
46 nohz_full, irqaffinity, rcu_nocbs. The format
47
48 <cpu number>,...,<cpu number>
49
50 or
51
52 <cpu number>-<cpu number>
53 (must be a positive range in ascending
54
55 or a mixture
56
57 <cpu number>,...,<cpu number>-<cpu number>
58
59 Note that for the special case of a range one
60 sized groups and for each group use some amoun
61 group:
62
63 <cpu number>-<cpu number>:<used size>/
64
65 For example one can add to the command line fo
66
67 isolcpus=1,2,10-20,100-2000:2/25
68
69 where the final item represents CPUs 100,101,1
70
71 The value "N" can be used to represent the num
72 i.e "foo_cpus=16-N" would be equivalent to "16
73
74 Keep in mind that "N" is dynamic, so if system
75 to change, such as less cores in the CPU list,
76 will also change. Use the same on a small 4 c
77 "16-3" and now the same boot input will be fla
78
79 The special case-tolerant group name "all" has
80 so that "nohz_full=all" is the equivalent of "
81
82 The semantics of "N" and "all" is supported on
83 all users of bitmap_parselist().
84
85 This document may not be entirely up to date a
86 "modinfo -p ${modulename}" shows a current lis
87 module. Loadable modules, after being loaded i
88 reveal their parameters in /sys/module/${modul
89 parameters may be changed at runtime by the co
90 ``echo -n ${value} > /sys/module/${modulename}
91
92 The parameters listed below are only valid if
93 were enabled and if respective hardware is pre
94 in alphabetical order. The text in square brac
95 of each description states the restrictions wi
96 is applicable::
97
98 ACPI ACPI support is enabled.
99 AGP AGP (Accelerated Graphics Port
100 ALSA ALSA sound support is enabled.
101 APIC APIC support is enabled.
102 APM Advanced Power Management supp
103 APPARMOR AppArmor support is enabled.
104 ARM ARM architecture is enabled.
105 ARM64 ARM64 architecture is enabled.
106 AX25 Appropriate AX.25 support is e
107 CLK Common clock infrastructure is
108 CMA Contiguous Memory Area support
109 DRM Direct Rendering Management su
110 DYNAMIC_DEBUG Build in debug messages
111 EARLY Parameter processed too early
112 EDD BIOS Enhanced Disk Drive Servi
113 EFI EFI Partitioning (GPT) is enab
114 EVM Extended Verification Module
115 FB The frame buffer device is ena
116 FTRACE Function tracing enabled.
117 GCOV GCOV profiling is enabled.
118 HIBERNATION HIBERNATION is enabled.
119 HW Appropriate hardware is enable
120 HYPER_V HYPERV support is enabled.
121 IMA Integrity measurement architec
122 IP_PNP IP DHCP, BOOTP, or RARP is ena
123 IPV6 IPv6 support is enabled.
124 ISAPNP ISA PnP code is enabled.
125 ISDN Appropriate ISDN support is en
126 ISOL CPU Isolation is enabled.
127 JOY Appropriate joystick support i
128 KGDB Kernel debugger support is ena
129 KVM Kernel Virtual Machine support
130 LIBATA Libata driver is enabled
131 LOONGARCH LoongArch architecture is en
132 LOOP Loopback device support is ena
133 LP Printer support is enabled.
134 M68k M68k architecture is enabled.
135 These options have mor
136 Documentation/arch/m68
137 MDA MDA console support is enabled
138 MIPS MIPS architecture is enabled.
139 MOUSE Appropriate mouse support is e
140 MSI Message Signaled Interrupts (P
141 MTD MTD (Memory Technology Device)
142 NET Appropriate network support is
143 NFS Appropriate NFS support is ena
144 NUMA NUMA support is enabled.
145 OF Devicetree is enabled.
146 PARISC The PA-RISC architecture is en
147 PCI PCI bus support is enabled.
148 PCIE PCI Express support is enabled
149 PCMCIA The PCMCIA subsystem is enable
150 PNP Plug & Play support is enabled
151 PPC PowerPC architecture is enable
152 PPT Parallel port support is enabl
153 PS2 Appropriate PS/2 support is en
154 PV_OPS A paravirtualized kernel is en
155 RAM RAM disk support is enabled.
156 RDT Intel Resource Director Techno
157 RISCV RISCV architecture is enabled.
158 S390 S390 architecture is enabled.
159 SCSI Appropriate SCSI support is en
160 A lot of drivers have
161 the Documentation/scsi
162 SECURITY Different security models are
163 SELINUX SELinux support is enabled.
164 SERIAL Serial support is enabled.
165 SH SuperH architecture is enabled
166 SMP The kernel is an SMP kernel.
167 SPARC Sparc architecture is enabled.
168 SUSPEND System suspend states are enab
169 SWSUSP Software suspend (hibernation)
170 TPM TPM drivers are enabled.
171 UMS USB Mass Storage support is en
172 USB USB support is enabled.
173 USBHID USB Human Interface Device sup
174 V4L Video For Linux support is ena
175 VGA The VGA console has been enabl
176 VMMIO Driver for memory mapped virti
177 VT Virtual terminal support is en
178 WDT Watchdog support is enabled.
179 X86-32 X86-32, aka i386 architecture
180 X86-64 X86-64 architecture is enabled
181 More X86-64 boot optio
182 Documentation/arch/x86
183 X86 Either 32-bit or 64-bit x86 (s
184 X86_UV SGI UV support is enabled.
185 XEN Xen support is enabled
186 XTENSA xtensa architecture is enabled
187
188 In addition, the following text indicates that
189
190 BOOT Is a boot loader parameter.
191 BUGS= Relates to possible processor
192 KNL Is a kernel start-up parameter
193
194 Parameters denoted with BOOT are actually inte
195 loader, and have no meaning to the kernel dire
196 Do not modify the syntax of boot loader parame
197 need or coordination with <Documentation/arch/
198
199 There are also arch-specific kernel-parameters
200 See for example <Documentation/arch/x86/x86_64
201
202 Note that ALL kernel parameters listed below a
203 a trailing = on the name of any parameter stat
204 be entered as an environment variable, whereas
205 it will appear as a kernel argument readable v
206 running once the system is up.
207
208 The number of kernel parameters is not limited
209 complete command line (parameters including sp
210 a fixed number of characters. This limit depen
211 and is between 256 and 4096 characters. It is
212 ./include/uapi/asm-generic/setup.h as COMMAND_
213
214 Finally, the [KMG] suffix is commonly describe
215 parameter values. These 'K', 'M', and 'G' lett
216 multipliers 'Kilo', 'Mega', and 'Giga', equali
217 bytes respectively. Such letter suffixes can a
218
219 .. include:: kernel-parameters.txt
220 :literal:
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