2022-04-09 13:29:29

by Tiezhu Yang

Subject: [PATCH 1/3] init: print some info about UUID and LABEL in name_to_dev_t()

If there is no valid initrd, but root=UUID or root=LABEL is used
in the command line, boot hangs like this:

[ 5.739815] VFS: Cannot open root device "UUID=19957230-2e15-494c-8dfa-84aab3591961" or unknown-block(0,0): error -6
[ 5.750280] Please append a correct "root=" boot option; here are the available partitions:
[ 5.856059] 0800 125034840 sda
[ 5.856061] driver: sd
[ 5.862124] 0801 307200 sda1 d5077411-3d87-4f85-b312-8cc309ef9073
[ 5.862128]
[ 5.870603] 0802 1048576 sda2 aae0dd30-e5f5-44e1-994e-d47bf5ce2e52
[ 5.870606]
[ 5.879080] 0803 52428800 sda3 759079ee-85fa-4636-9de7-1ac0643ab87e
[ 5.879083]
[ 5.887558] 0804 8388608 sda4 439c4b0a-7b4f-4434-82f1-f9d380b55fb9
[ 5.887560]
[ 5.896035] 0805 62860288 sda5 ee52e951-1315-4fab-a3e5-45c6eeae6ce6
[ 5.910575] Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)
[ 5.918796] ---[ end Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0) ]---

The above log is very useful, but some users still need time
to analysis the cause [1, 2]. It is better to print some info
to explicitly tell the users root=UUID or root=LABEL is not
supported without initrd.

[1] https://unix.stackexchange.com/questions/93767/why-cant-i-specify-my-root-fs-with-a-uuid
[2] https://unix.stackexchange.com/questions/302795/how-to-identify-root-partition-via-uuid-without-initramfs-initrd

Signed-off-by: Tiezhu Yang <[email protected]>
---
init/do_mounts.c | 8 ++++++++
1 file changed, 8 insertions(+)

diff --git a/init/do_mounts.c b/init/do_mounts.c
index 7058e14..2c1c492 100644
--- a/init/do_mounts.c
+++ b/init/do_mounts.c
@@ -290,6 +290,14 @@ dev_t name_to_dev_t(const char *name)
if (strncmp(name, "/dev/", 5) == 0)
return devt_from_devname(name + 5);
#endif
+ if (strncmp(name, "UUID=", 5) == 0) {
+ pr_info("root=UUID is not supported without initrd\n");
+ return 0;
+ }
+ if (strncmp(name, "LABEL=", 6) == 0) {
+ pr_info("root=LABEL is not supported without initrd\n");
+ return 0;
+ }
return devt_from_devnum(name);
}
EXPORT_SYMBOL_GPL(name_to_dev_t);
--
2.1.0

2022-04-12 20:46:05

by Christoph Hellwig

Subject: Re: [PATCH 1/3] init: print some info about UUID and LABEL in name_to_dev_t()

On Sat, Apr 09, 2022 at 11:39:39AM +0800, Tiezhu Yang wrote:
> If there is no valid initrd, but root=UUID or root=LABEL is used
> in the command line, boot hangs like this:

There is no root=UUID or root=LABEL handling in the kernel at all, so
I don't see why we should print anything here.