Commit f2d34fd9 authored by Will Drewry's avatar Will Drewry Committed by Linus Torvalds

Documentation: add pointer to name_to_dev_t for root= values

Update kernel-parameters.txt to point users to the authoritative comment
for name_to_dev_t.  In addition, updates other places where some
name_to_dev_t behavior was discussed.  All other references to root=
appear to be for explicit sample usage or just side comments when
discussing other kernel parameters.
Signed-off-by: default avatarWill Drewry <>
Cc: Kay Sievers <>
Cc: Randy Dunlap <>
Cc: Namhyung Kim <>
Cc: Trond Myklebust <>
Cc: Jens Axboe <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 2af14162
......@@ -106,13 +106,20 @@ separated by spaces:
To use the first on-chip serial port at baud rate 115200, no parity, 8
bits, and no flow control.
(*) root=/dev/<xxxx>
(*) root=<xxxx>
This specifies the device upon which the root filesystem resides. For
This specifies the device upon which the root filesystem resides. It
may be specified by major and minor number, device path, or even
partition uuid, if supported. For example:
/dev/nfs NFS root filesystem
/dev/mtdblock3 Fourth RedBoot partition on the System Flash
first partition after the partition with the given UUID
253:0 Device with major 253 and minor 0
Authoritative information can be found in
(*) rw
......@@ -2245,6 +2245,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
ro [KNL] Mount root device read-only on boot
root= [KNL] Root filesystem
See name_to_dev_t comment in init/do_mounts.c.
rootdelay= [KNL] Delay (in seconds) to pause before attempting to
mount the root filesystem
......@@ -129,6 +129,20 @@ decimal 11 is the major of SCSI CD-ROMs, and the minor 0 stands for
the first of these. You can find out all valid major numbers by
looking into include/linux/major.h.
In addition to major and minor numbers, if the device containing your
root partition uses a partition table format with unique partition
identifiers, then you may use them. For instance,
"root=PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF". It is also
possible to reference another partition on the same device using a
known partition UUID as the starting point. For example,
if partition 5 of the device has the UUID of
00112233-4455-6677-8899-AABBCCDDEEFF then partition 3 may be found as
Authoritative information can be found in
2.2) ro, rw
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