[PATCH v2 0/3] initrd: remove half of classic initrd support

[PATCH v2 0/3] initrd: remove half of classic initrd support

[Askar Safin]

Intro
====
This patchset removes half of classic initrd (initial RAM disk) support,
i. e. linuxrc code path, which was deprecated in 2020.
Initramfs still stays, RAM disk itself (brd) still stays.
And other half of initrd stays, too.
init/do_mounts* are listed in VFS entry in
MAINTAINERS, so I think this patchset should go through VFS tree.
I tested the patchset on 8 (!!!) archs in Qemu (see details below).
If you still use initrd, see below for workaround.

In 2020 deprecation notice was put to linuxrc initrd code path.
In previous version of this patchset I tried to remove initrd
fully, but Nicolas Schichan reported that he still uses
other code path (root=/dev/ram0 one) on million devices [4].
root=/dev/ram0 code path did not contain deprecation notice.

So, in this version of patchset I remove deprecated code path,
i. e. linuxrc one, while keeping other, i. e. root=/dev/ram0 one.

Also I put deprecation notice to remaining code path, i. e. to
root=/dev/ram0 one. I plan to send patches for full removal
of initrd after one year, i. e. in September 2026 (of course,
initramfs will still work).

Also, I tried to make this patchset small to make sure it
can be reverted easily. I plan to send cleanups later.

Details
====
Other user-visible changes:

- Removed kernel command line parameters "load_ramdisk" and
"prompt_ramdisk", which did nothing and were deprecated
- Removed /proc/sys/kernel/real-root-dev . It was used
for initrd only
- Command line parameters "noinitrd" and "ramdisk_start=" are deprecated

This patchset is based on current mainline (7f7072574127).

Testing
====
I tested my patchset on many architectures in Qemu using my Rust
program, heavily based on mkroot [1].

I used the following cross-compilers:

aarch64-linux-musleabi
armv4l-linux-musleabihf
armv5l-linux-musleabihf
armv7l-linux-musleabihf
i486-linux-musl
i686-linux-musl
mips-linux-musl
mips64-linux-musl
mipsel-linux-musl
powerpc-linux-musl
powerpc64-linux-musl
powerpc64le-linux-musl
riscv32-linux-musl
riscv64-linux-musl
s390x-linux-musl
sh4-linux-musl
sh4eb-linux-musl
x86_64-linux-musl

taken from this directory [2].

So, as you can see, there are 18 triplets, which correspond to 8 subdirs in arch/.

For every triplet I tested that:
- Initramfs still works (both builtin and external)
- Direct boot from disk still works
- Remaining initrd code path (root=/dev/ram0) still works

Workaround
====
If "retain_initrd" is passed to kernel, then initramfs/initrd,
passed by bootloader, is retained and becomes available after boot
as read-only magic file /sys/firmware/initrd [3].

No copies are involved. I. e. /sys/firmware/initrd is simply
a reference to original blob passed by bootloader.

This works even if initrd/initramfs is not recognized by kernel
in any way, i. e. even if it is not valid cpio archive, nor
a fs image supported by classic initrd.

This works both with my patchset and without it.

This means that you can emulate classic initrd so:
link builtin initramfs to kernel; in /init in this initramfs
copy /sys/firmware/initrd to some file in / and loop-mount it.

This is even better than classic initrd, because:
- You can use fs not supported by classic initrd, for example erofs
- One copy is involved (from /sys/firmware/initrd to some file in /)
as opposed to two when using classic initrd

Still, I don't recommend using this workaround, because
I want everyone to migrate to proper modern initramfs.
But still you can use this workaround if you want.

Also: it is not possible to directly loop-mount
/sys/firmware/initrd . Theoretically kernel can be changed
to allow this (and/or to make it writable), but I think nobody needs this.
And I don't want to implement this.

On Qemu's -initrd and GRUB's initrd
====
Don't panic, this patchset doesn't remove initramfs
(which is used by nearly all Linux distros). And I don't
have plans to remove it.

Qemu's -initrd option and GRUB's initrd command refer
to initrd bootloader mechanism, which is used to
load both initrd and (external) initramfs.

So, if you use Qemu's -initrd or GRUB's initrd,
then you likely use them to pass initramfs, and thus
you are safe.

v1: https://lore.kernel.org/lkml/20250913003842.41944-1-safinaskar@gmail.com/

v1 -> v2 changes:
- A lot. I removed most patches, see cover letter for details

[1] https://github.com/landley/toybox/tree/master/mkroot
[2] https://landley.net/toybox/downloads/binaries/toolchains/latest
[3] https://lore.kernel.org/all/20231207235654.16622-1-graf@amazon.com/
[4] https://lore.kernel.org/lkml/20250918152830.438554-1-nschichan@freebox.fr/

Askar Safin (3):
  init: remove deprecated "load_ramdisk" and "prompt_ramdisk" command
    line parameters
  initrd: remove deprecated code path (linuxrc)
  init: remove /proc/sys/kernel/real-root-dev

 .../admin-guide/kernel-parameters.txt         |   8 +-
 Documentation/admin-guide/sysctl/kernel.rst   |   6 -
 arch/arm/configs/neponset_defconfig           |   2 +-
 fs/init.c                                     |  14 ---
 include/linux/init_syscalls.h                 |   1 -
 include/linux/initrd.h                        |   2 -
 include/uapi/linux/sysctl.h                   |   1 -
 init/do_mounts.c                              |  11 +-
 init/do_mounts.h                              |  18 +--
 init/do_mounts_initrd.c                       | 105 +-----------------
 init/do_mounts_rd.c                           |  24 +---
 11 files changed, 18 insertions(+), 174 deletions(-)


base-commit: 7f7072574127c9e971cad83a0274e86f6275c0d5
-- 
2.47.3

[PATCH v2 1/3] init: remove deprecated "load_ramdisk" and "prompt_ramdisk" command line parameters

[Askar Safin]

...which do nothing. They were deprecated (in documentation) in
6b99e6e6aa62 ("Documentation/admin-guide: blockdev/ramdisk: remove use of
"rdev"") and in kernel messages in c8376994c86c ("initrd: remove support
for multiple floppies")

Signed-off-by: Askar Safin <safinaskar@gmail.com>
---
 Documentation/admin-guide/kernel-parameters.txt | 4 ----
 arch/arm/configs/neponset_defconfig             | 2 +-
 init/do_mounts.c                                | 7 -------
 init/do_mounts_rd.c                             | 7 -------
 4 files changed, 1 insertion(+), 19 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index e019db1633fd..521ab3425504 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3280,8 +3280,6 @@
 			If there are multiple matching configurations changing
 			the same attribute, the last one is used.
 
-	load_ramdisk=	[RAM] [Deprecated]
-
 	lockd.nlm_grace_period=P  [NFS] Assign grace period.
 			Format: <integer>
 
@@ -5245,8 +5243,6 @@
 			Param: <number> - step/bucket size as a power of 2 for
 				statistical time based profiling.
 
-	prompt_ramdisk=	[RAM] [Deprecated]
-
 	prot_virt=	[S390] enable hosting protected virtual machines
 			isolated from the hypervisor (if hardware supports
 			that). If enabled, the default kernel base address
diff --git a/arch/arm/configs/neponset_defconfig b/arch/arm/configs/neponset_defconfig
index 2227f86100ad..4d720001c12e 100644
--- a/arch/arm/configs/neponset_defconfig
+++ b/arch/arm/configs/neponset_defconfig
@@ -9,7 +9,7 @@ CONFIG_ASSABET_NEPONSET=y
 CONFIG_ZBOOT_ROM_TEXT=0x80000
 CONFIG_ZBOOT_ROM_BSS=0xc1000000
 CONFIG_ZBOOT_ROM=y
-CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) load_ramdisk=1 prompt_ramdisk=0 mem=32M noinitrd initrd=0xc0800000,3M"
+CONFIG_CMDLINE="console=ttySA0,38400n8 cpufreq=221200 rw root=/dev/mtdblock2 mtdparts=sa1100:512K(boot),1M(kernel),2560K(initrd),4M(root) mem=32M noinitrd initrd=0xc0800000,3M"
 CONFIG_FPE_NWFPE=y
 CONFIG_PM=y
 CONFIG_MODULES=y
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 6af29da8889e..0f2f44e6250c 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -34,13 +34,6 @@ static int root_wait;
 
 dev_t ROOT_DEV;
 
-static int __init load_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated load_ramdisk= option\n");
-	return 1;
-}
-__setup("load_ramdisk=", load_ramdisk);
-
 static int __init readonly(char *str)
 {
 	if (*str)
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 19d9f33dcacf..5311f2d7edc8 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -18,13 +18,6 @@
 static struct file *in_file, *out_file;
 static loff_t in_pos, out_pos;
 
-static int __init prompt_ramdisk(char *str)
-{
-	pr_warn("ignoring the deprecated prompt_ramdisk= option\n");
-	return 1;
-}
-__setup("prompt_ramdisk=", prompt_ramdisk);
-
 int __initdata rd_image_start;		/* starting block # of image */
 
 static int __init ramdisk_start_setup(char *str)
-- 
2.47.3

Re: [PATCH v2 1/3] init: remove deprecated "load_ramdisk" and "prompt_ramdisk" command line parameters

[Andy Shevchenko]

On Fri, Oct 10, 2025 at 12:42 PM Askar Safin <safinaskar@gmail.com> wrote:
>
> ...which do nothing. They were deprecated (in documentation) in
> 6b99e6e6aa62 ("Documentation/admin-guide: blockdev/ramdisk: remove use of
> "rdev"") and in kernel messages in c8376994c86c ("initrd: remove support
> for multiple floppies")

With all the respect to the work and the series I have noted this:
1) often the last period is missing in the commit messages;
2) in this change it's unclear for how long (years) the feature was
deprecated, i.e. the other patch states that 2020 for something else.
I wonder if this one has the similar order of oldness.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 1/3] init: remove deprecated "load_ramdisk" and "prompt_ramdisk" command line parameters

[Askar Safin]

On Fri, Oct 10, 2025 at 6:02 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> 1) often the last period is missing in the commit messages;
I will fix in v3.

> 2) in this change it's unclear for how long (years) the feature was
> deprecated, i.e. the other patch states that 2020 for something else.
> I wonder if this one has the similar order of oldness.

These two commits were done in 2020, too. I will fix in v3.

--
Askar Safin

[PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Askar Safin]

Remove linuxrc initrd code path, which was deprecated in 2020.

Initramfs and (non-initial) RAM disks (i. e. brd) still work.

Both built-in and bootloader-supplied initramfs still work.

Non-linuxrc initrd code path (i. e. using /dev/ram as final root
filesystem) still works, but I put deprecation message into it

Signed-off-by: Askar Safin <safinaskar@gmail.com>
---
 .../admin-guide/kernel-parameters.txt         |  4 +-
 fs/init.c                                     | 14 ---
 include/linux/init_syscalls.h                 |  1 -
 include/linux/initrd.h                        |  2 -
 init/do_mounts.c                              |  4 +-
 init/do_mounts.h                              | 18 +---
 init/do_mounts_initrd.c                       | 85 ++-----------------
 init/do_mounts_rd.c                           | 17 +---
 8 files changed, 17 insertions(+), 128 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 521ab3425504..24d8899d8a39 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4285,7 +4285,7 @@
 			Note that this argument takes precedence over
 			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
 
-	noinitrd	[RAM] Tells the kernel not to load any configured
+	noinitrd	[Deprecated,RAM] Tells the kernel not to load any configured
 			initial RAM disk.
 
 	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
@@ -5299,7 +5299,7 @@
 	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
 			See Documentation/admin-guide/blockdev/ramdisk.rst.
 
-	ramdisk_start=	[RAM] RAM disk image start address
+	ramdisk_start=	[Deprecated,RAM] RAM disk image start address
 
 	random.trust_cpu=off
 			[KNL,EARLY] Disable trusting the use of the CPU's
diff --git a/fs/init.c b/fs/init.c
index 07f592ccdba8..60719494d9a0 100644
--- a/fs/init.c
+++ b/fs/init.c
@@ -27,20 +27,6 @@ int __init init_mount(const char *dev_name, const char *dir_name,
 	return ret;
 }
 
-int __init init_umount(const char *name, int flags)
-{
-	int lookup_flags = LOOKUP_MOUNTPOINT;
-	struct path path;
-	int ret;
-
-	if (!(flags & UMOUNT_NOFOLLOW))
-		lookup_flags |= LOOKUP_FOLLOW;
-	ret = kern_path(name, lookup_flags, &path);
-	if (ret)
-		return ret;
-	return path_umount(&path, flags);
-}
-
 int __init init_chdir(const char *filename)
 {
 	struct path path;
diff --git a/include/linux/init_syscalls.h b/include/linux/init_syscalls.h
index 92045d18cbfc..0bdbc458a881 100644
--- a/include/linux/init_syscalls.h
+++ b/include/linux/init_syscalls.h
@@ -2,7 +2,6 @@
 
 int __init init_mount(const char *dev_name, const char *dir_name,
 		const char *type_page, unsigned long flags, void *data_page);
-int __init init_umount(const char *name, int flags);
 int __init init_chdir(const char *filename);
 int __init init_chroot(const char *filename);
 int __init init_chown(const char *filename, uid_t user, gid_t group, int flags);
diff --git a/include/linux/initrd.h b/include/linux/initrd.h
index f1a1f4c92ded..7e5d26c8136f 100644
--- a/include/linux/initrd.h
+++ b/include/linux/initrd.h
@@ -3,8 +3,6 @@
 #ifndef __LINUX_INITRD_H
 #define __LINUX_INITRD_H
 
-#define INITRD_MINOR 250 /* shouldn't collide with /dev/ram* too soon ... */
-
 /* starting block # of image */
 extern int rd_image_start;
 
diff --git a/init/do_mounts.c b/init/do_mounts.c
index 0f2f44e6250c..1054ad3c905a 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -476,13 +476,11 @@ void __init prepare_namespace(void)
 	if (saved_root_name[0])
 		ROOT_DEV = parse_root_device(saved_root_name);
 
-	if (initrd_load(saved_root_name))
-		goto out;
+	initrd_load();
 
 	if (root_wait)
 		wait_for_root(saved_root_name);
 	mount_root(saved_root_name);
-out:
 	devtmpfs_mount();
 	init_mount(".", "/", NULL, MS_MOVE, NULL);
 	init_chroot(".");
diff --git a/init/do_mounts.h b/init/do_mounts.h
index 6069ea3eb80d..a386ee5314c9 100644
--- a/init/do_mounts.h
+++ b/init/do_mounts.h
@@ -23,25 +23,15 @@ static inline __init int create_dev(char *name, dev_t dev)
 }
 
 #ifdef CONFIG_BLK_DEV_RAM
-
-int __init rd_load_disk(int n);
-int __init rd_load_image(char *from);
-
+int __init rd_load_image(void);
 #else
-
-static inline int rd_load_disk(int n) { return 0; }
-static inline int rd_load_image(char *from) { return 0; }
-
+static inline int rd_load_image(void) { return 0; }
 #endif
 
 #ifdef CONFIG_BLK_DEV_INITRD
-bool __init initrd_load(char *root_device_name);
+void __init initrd_load(void);
 #else
-static inline bool initrd_load(char *root_device_name)
-{
-	return false;
-	}
-
+static inline void initrd_load(void) { }
 #endif
 
 /* Ensure that async file closing finished to prevent spurious errors. */
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index f6867bad0d78..d4f5f4c60a22 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -2,13 +2,7 @@
 #include <linux/unistd.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>
-#include <linux/minix_fs.h>
-#include <linux/romfs_fs.h>
 #include <linux/initrd.h>
-#include <linux/sched.h>
-#include <linux/freezer.h>
-#include <linux/kmod.h>
-#include <uapi/linux/mount.h>
 
 #include "do_mounts.h"
 
@@ -41,6 +35,7 @@ late_initcall(kernel_do_mounts_initrd_sysctls_init);
 
 static int __init no_initrd(char *str)
 {
+	pr_warn("noinitrd option is deprecated and will be removed soon\n");
 	mount_initrd = 0;
 	return 1;
 }
@@ -70,85 +65,17 @@ static int __init early_initrd(char *p)
 }
 early_param("initrd", early_initrd);
 
-static int __init init_linuxrc(struct subprocess_info *info, struct cred *new)
-{
-	ksys_unshare(CLONE_FS | CLONE_FILES);
-	console_on_rootfs();
-	/* move initrd over / and chdir/chroot in initrd root */
-	init_chdir("/root");
-	init_mount(".", "/", NULL, MS_MOVE, NULL);
-	init_chroot(".");
-	ksys_setsid();
-	return 0;
-}
-
-static void __init handle_initrd(char *root_device_name)
-{
-	struct subprocess_info *info;
-	static char *argv[] = { "linuxrc", NULL, };
-	extern char *envp_init[];
-	int error;
-
-	pr_warn("using deprecated initrd support, will be removed soon.\n");
-
-	real_root_dev = new_encode_dev(ROOT_DEV);
-	create_dev("/dev/root.old", Root_RAM0);
-	/* mount initrd on rootfs' /root */
-	mount_root_generic("/dev/root.old", root_device_name,
-			   root_mountflags & ~MS_RDONLY);
-	init_mkdir("/old", 0700);
-	init_chdir("/old");
-
-	info = call_usermodehelper_setup("/linuxrc", argv, envp_init,
-					 GFP_KERNEL, init_linuxrc, NULL, NULL);
-	if (!info)
-		return;
-	call_usermodehelper_exec(info, UMH_WAIT_PROC|UMH_FREEZABLE);
-
-	/* move initrd to rootfs' /old */
-	init_mount("..", ".", NULL, MS_MOVE, NULL);
-	/* switch root and cwd back to / of rootfs */
-	init_chroot("..");
-
-	if (new_decode_dev(real_root_dev) == Root_RAM0) {
-		init_chdir("/old");
-		return;
-	}
-
-	init_chdir("/");
-	ROOT_DEV = new_decode_dev(real_root_dev);
-	mount_root(root_device_name);
-
-	printk(KERN_NOTICE "Trying to move old root to /initrd ... ");
-	error = init_mount("/old", "/root/initrd", NULL, MS_MOVE, NULL);
-	if (!error)
-		printk("okay\n");
-	else {
-		if (error == -ENOENT)
-			printk("/initrd does not exist. Ignored.\n");
-		else
-			printk("failed\n");
-		printk(KERN_NOTICE "Unmounting old root\n");
-		init_umount("/old", MNT_DETACH);
-	}
-}
-
-bool __init initrd_load(char *root_device_name)
+void __init initrd_load(void)
 {
 	if (mount_initrd) {
 		create_dev("/dev/ram", Root_RAM0);
 		/*
-		 * Load the initrd data into /dev/ram0. Execute it as initrd
-		 * unless /dev/ram0 is supposed to be our actual root device,
-		 * in that case the ram disk is just set up here, and gets
-		 * mounted in the normal path.
+		 * Load the initrd data into /dev/ram0.
 		 */
-		if (rd_load_image("/initrd.image") && ROOT_DEV != Root_RAM0) {
-			init_unlink("/initrd.image");
-			handle_initrd(root_device_name);
-			return true;
+		if (rd_load_image()) {
+			pr_warn("using deprecated initrd support, will be removed in September 2026; "
+				"use initramfs instead or (as a last resort) /sys/firmware/initrd.\n");
 		}
 	}
 	init_unlink("/initrd.image");
-	return false;
 }
diff --git a/init/do_mounts_rd.c b/init/do_mounts_rd.c
index 5311f2d7edc8..0a021bbcd501 100644
--- a/init/do_mounts_rd.c
+++ b/init/do_mounts_rd.c
@@ -22,6 +22,7 @@ int __initdata rd_image_start;		/* starting block # of image */
 
 static int __init ramdisk_start_setup(char *str)
 {
+	pr_warn("ramdisk_start= option is deprecated and will be removed soon\n");
 	rd_image_start = simple_strtol(str,NULL,0);
 	return 1;
 }
@@ -177,7 +178,7 @@ static unsigned long nr_blocks(struct file *file)
 	return i_size_read(inode) >> 10;
 }
 
-int __init rd_load_image(char *from)
+int __init rd_load_image(void)
 {
 	int res = 0;
 	unsigned long rd_blocks, devblocks, nr_disks;
@@ -191,7 +192,7 @@ int __init rd_load_image(char *from)
 	if (IS_ERR(out_file))
 		goto out;
 
-	in_file = filp_open(from, O_RDONLY, 0);
+	in_file = filp_open("/initrd.image", O_RDONLY, 0);
 	if (IS_ERR(in_file))
 		goto noclose_input;
 
@@ -220,10 +221,7 @@ int __init rd_load_image(char *from)
 	/*
 	 * OK, time to copy in the data
 	 */
-	if (strcmp(from, "/initrd.image") == 0)
-		devblocks = nblocks;
-	else
-		devblocks = nr_blocks(in_file);
+	devblocks = nblocks;
 
 	if (devblocks == 0) {
 		printk(KERN_ERR "RAMDISK: could not determine device size\n");
@@ -267,13 +265,6 @@ int __init rd_load_image(char *from)
 	return res;
 }
 
-int __init rd_load_disk(int n)
-{
-	create_dev("/dev/root", ROOT_DEV);
-	create_dev("/dev/ram", MKDEV(RAMDISK_MAJOR, n));
-	return rd_load_image("/dev/root");
-}
-
 static int exit_code;
 static int decompress_error;
 
-- 
2.47.3

Re: [PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Andy Shevchenko]

On Fri, Oct 10, 2025 at 12:42 PM Askar Safin <safinaskar@gmail.com> wrote:
>
> Remove linuxrc initrd code path, which was deprecated in 2020.
>
> Initramfs and (non-initial) RAM disks (i. e. brd) still work.
>
> Both built-in and bootloader-supplied initramfs still work.
>
> Non-linuxrc initrd code path (i. e. using /dev/ram as final root
> filesystem) still works, but I put deprecation message into it

...

> -       noinitrd        [RAM] Tells the kernel not to load any configured
> +       noinitrd        [Deprecated,RAM] Tells the kernel not to load any configured
>                         initial RAM disk.

How one is supposed to run this when just having a kernel is enough?
At least (ex)colleague of mine was a heavy user of this option for
testing kernel builds on the real HW.

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Askar Safin]

On Fri, Oct 10, 2025 at 6:05 PM Andy Shevchenko
<andy.shevchenko@gmail.com> wrote:
> > -       noinitrd        [RAM] Tells the kernel not to load any configured
> > +       noinitrd        [Deprecated,RAM] Tells the kernel not to load any configured
> >                         initial RAM disk.
>
> How one is supposed to run this when just having a kernel is enough?
> At least (ex)colleague of mine was a heavy user of this option for
> testing kernel builds on the real HW.

This option applies to initrd only, not to initramfs.
Except for EFI mode, when it applies to both.

I will remove this option when I remove initrd.

In EFI mode it is easy just not to pass initramfs, so all is okay.

Also I will clarify docs in v3.

Also, please, answer here:
https://lore.kernel.org/regressions/20250918183336.5633-1-safinaskar@gmail.com/

-- 
Askar Safin

Re: [PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Randy Dunlap]

Hi,

On 10/10/25 2:40 AM, Askar Safin wrote:
> Remove linuxrc initrd code path, which was deprecated in 2020.
> 
> Initramfs and (non-initial) RAM disks (i. e. brd) still work.
> 
> Both built-in and bootloader-supplied initramfs still work.
> 
> Non-linuxrc initrd code path (i. e. using /dev/ram as final root
> filesystem) still works, but I put deprecation message into it
> 
> Signed-off-by: Askar Safin <safinaskar@gmail.com>
> ---
>  .../admin-guide/kernel-parameters.txt         |  4 +-
>  fs/init.c                                     | 14 ---
>  include/linux/init_syscalls.h                 |  1 -
>  include/linux/initrd.h                        |  2 -
>  init/do_mounts.c                              |  4 +-
>  init/do_mounts.h                              | 18 +---
>  init/do_mounts_initrd.c                       | 85 ++-----------------
>  init/do_mounts_rd.c                           | 17 +---
>  8 files changed, 17 insertions(+), 128 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 521ab3425504..24d8899d8a39 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -4285,7 +4285,7 @@
>  			Note that this argument takes precedence over
>  			the CONFIG_RCU_NOCB_CPU_DEFAULT_ALL option.
>  
> -	noinitrd	[RAM] Tells the kernel not to load any configured
> +	noinitrd	[Deprecated,RAM] Tells the kernel not to load any configured
>  			initial RAM disk.
>  
>  	nointremap	[X86-64,Intel-IOMMU,EARLY] Do not enable interrupt
> @@ -5299,7 +5299,7 @@
>  	ramdisk_size=	[RAM] Sizes of RAM disks in kilobytes
>  			See Documentation/admin-guide/blockdev/ramdisk.rst.
>  
> -	ramdisk_start=	[RAM] RAM disk image start address
> +	ramdisk_start=	[Deprecated,RAM] RAM disk image start address
>  
>  	random.trust_cpu=off
>  			[KNL,EARLY] Disable trusting the use of the CPU's

There are more places in Documentation/ that refer to "linuxrc".
Should those also be removed or fixed?

accounting/delay-accounting.rst
admin-guide/initrd.rst
driver-api/early-userspace/early_userspace_support.rst
power/swsusp-dmcrypt.rst
translations/zh_CN/accounting/delay-accounting.rst


Thanks.

Re: [PATCH v2 2/3] initrd: remove deprecated code path (linuxrc)

[Askar Safin]

On Fri, Oct 10, 2025 at 10:31 PM Randy Dunlap <rdunlap@infradead.org> wrote:
> There are more places in Documentation/ that refer to "linuxrc".
> Should those also be removed or fixed?
>
> accounting/delay-accounting.rst
> admin-guide/initrd.rst
> driver-api/early-userspace/early_userspace_support.rst
> power/swsusp-dmcrypt.rst
> translations/zh_CN/accounting/delay-accounting.rst

Yes, they should be removed.
I made this patchset minimal to be sure it is easy to revert.
I will remove these linuxrc mentions in cleanup patchset.

-- 
Askar Safin

[PATCH v2 3/3] init: remove /proc/sys/kernel/real-root-dev

[Askar Safin]

It is not used anymore

Signed-off-by: Askar Safin <safinaskar@gmail.com>
---
 Documentation/admin-guide/sysctl/kernel.rst |  6 ------
 include/uapi/linux/sysctl.h                 |  1 -
 init/do_mounts_initrd.c                     | 20 --------------------
 3 files changed, 27 deletions(-)

diff --git a/Documentation/admin-guide/sysctl/kernel.rst b/Documentation/admin-guide/sysctl/kernel.rst
index 8b49eab937d0..cc958c228bc2 100644
--- a/Documentation/admin-guide/sysctl/kernel.rst
+++ b/Documentation/admin-guide/sysctl/kernel.rst
@@ -1215,12 +1215,6 @@ that support this feature.
 ==  ===========================================================================
 
 
-real-root-dev
-=============
-
-See Documentation/admin-guide/initrd.rst.
-
-
 reboot-cmd (SPARC only)
 =======================
 
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index 63d1464cb71c..1c7fe0f4dca4 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -92,7 +92,6 @@ enum
 	KERN_DOMAINNAME=8,	/* string: domainname */
 
 	KERN_PANIC=15,		/* int: panic timeout */
-	KERN_REALROOTDEV=16,	/* real root device to mount after initrd */
 
 	KERN_SPARC_REBOOT=21,	/* reboot command on Sparc */
 	KERN_CTLALTDEL=22,	/* int: allow ctl-alt-del to reboot */
diff --git a/init/do_mounts_initrd.c b/init/do_mounts_initrd.c
index d4f5f4c60a22..fb0c9d3b722f 100644
--- a/init/do_mounts_initrd.c
+++ b/init/do_mounts_initrd.c
@@ -8,31 +8,11 @@
 
 unsigned long initrd_start, initrd_end;
 int initrd_below_start_ok;
-static unsigned int real_root_dev;	/* do_proc_dointvec cannot handle kdev_t */
 static int __initdata mount_initrd = 1;
 
 phys_addr_t phys_initrd_start __initdata;
 unsigned long phys_initrd_size __initdata;
 
-#ifdef CONFIG_SYSCTL
-static const struct ctl_table kern_do_mounts_initrd_table[] = {
-	{
-		.procname       = "real-root-dev",
-		.data           = &real_root_dev,
-		.maxlen         = sizeof(int),
-		.mode           = 0644,
-		.proc_handler   = proc_dointvec,
-	},
-};
-
-static __init int kernel_do_mounts_initrd_sysctls_init(void)
-{
-	register_sysctl_init("kernel", kern_do_mounts_initrd_table);
-	return 0;
-}
-late_initcall(kernel_do_mounts_initrd_sysctls_init);
-#endif /* CONFIG_SYSCTL */
-
 static int __init no_initrd(char *str)
 {
 	pr_warn("noinitrd option is deprecated and will be removed soon\n");
-- 
2.47.3