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#1 2010-10-07 06:00:26

miro279
Member
Registered: 2010-10-02
Posts: 153

[SOLVED] mtab forgets device via UUID

Hello,

my hd is mounted via UUID (seems to be standard with arch installation), its just that for one of the partitions the UUID is nozt changed into a device-name like /dev/sda3.
So if I do a df the output is:

udev                     10240       216     10024   3% /dev
/dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e
                      10323128   4663572   5135272  48% /
shm                    1019152         0   1019152   0% /dev/shm
/dev/sda4            142416680   6951072 128231260   6% /home
/dev/sda1                64240     14662     46252  25% /boot

same is true for /etc/mtab and /proc/mounts. At which time is the name-switching between UUID and normal device names made?

Thanks a lot in advance!

Last edited by miro279 (2010-10-07 18:17:38)

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#2 2010-10-07 11:39:08

karol
Archivist
Registered: 2009-05-06
Posts: 25,440

Re: [SOLVED] mtab forgets device via UUID

It's a known "bug".

A similar one was closed: https://bugs.archlinux.org/task/19785

Last edited by karol (2010-10-07 11:48:42)

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#3 2010-10-07 12:35:22

miro279
Member
Registered: 2010-10-02
Posts: 153

Re: [SOLVED] mtab forgets device via UUID

for me in every output I can only find the UUID for /dev/sda3:

findmnt -rnu -o SOURCE,TARGET,FSTYPE,OPTIONS
proc /proc proc rw,relatime
sys /sys sysfs rw,relatime
udev /dev devtmpfs rw,nosuid,relatime,size=10240k,nr_inodes=218530,mode=755
/dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e / ext4 rw,relatime,barrier=1,data=ordered
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000
shm /dev/shm tmpfs rw,nosuid,nodev,relatime
/dev/sda4 /home ext4 rw,relatime,barrier=1,data=ordered
/dev/sda1 /boot ext2 rw,relatime,errors=continue

and also

cat /proc/self/mountinfo 
12 15 0:3 / /proc rw,relatime - proc proc rw
13 15 0:12 / /sys rw,relatime - sysfs sys rw
14 15 0:5 / /dev rw,nosuid,relatime - devtmpfs udev rw,size=10240k,nr_inodes=218530,mode=755
15 1 8:3 / / rw,relatime - ext4 /dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e rw,barrier=1,data=ordered
18 14 0:10 / /dev/pts rw,relatime - devpts devpts rw,mode=600,ptmxmode=000
19 14 0:15 / /dev/shm rw,nosuid,nodev,relatime - tmpfs shm rw
20 15 8:4 / /home rw,relatime - ext4 /dev/sda4 rw,barrier=1,data=ordered
21 15 8:1 / /boot rw,relatime - ext2 /dev/sda1 rw,errors=continue

Where is the source for all of this?

Also, blkid does know the right translation:

blkid 
/dev/sda1: UUID="dd98976f-fc27-4a32-8db7-d92fa36317e4" TYPE="ext2" 
/dev/sda2: UUID="28955678-413a-4fd5-a459-2b129667c94e" TYPE="swap" 
/dev/sda3: UUID="8d2a1a14-7050-41d3-b7ca-f5460ab6770e" TYPE="ext4" 
/dev/sda4: UUID="b3d9152c-61f2-4fb2-89d3-337ee1764b04" TYPE="ext4"

for some reason its just not passed to mtab for one of these devices.. strange problem

Last edited by miro279 (2010-10-07 12:48:15)

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#4 2010-10-07 12:47:50

karol
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Registered: 2009-05-06
Posts: 25,440

Re: [SOLVED] mtab forgets device via UUID

Have you read 'man findmnt'?

findmnt --fstab --evaluate

You can patch your initscripts or make some aliases if you prefer the values to be shown in another way: http://projects.archlinux.org/initscrip … 84a8d1536e

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#5 2010-10-07 13:09:07

miro279
Member
Registered: 2010-10-02
Posts: 153

Re: [SOLVED] mtab forgets device via UUID

the problem is that both outputs only show the uuid:

/bin/findmnt -rnu -o SOURCE,TARGET,FSTYPE,OPTIONS

proc /proc proc rw,relatime
sys /sys sysfs rw,relatime
udev /dev devtmpfs rw,nosuid,relatime,size=10240k,nr_inodes=218530,mode=755
/dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e / ext4 rw,relatime,barrier=1,data=ordered
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000
shm /dev/shm tmpfs rw,nosuid,nodev,relatime
/dev/sda4 /home ext4 rw,relatime,barrier=1,data=ordered
/dev/sda1 /boot ext2 rw,relatime,errors=continue

and
cat /proc/mounts

rootfs / rootfs rw 0 0
proc /proc proc rw,relatime 0 0
sys /sys sysfs rw,relatime 0 0
udev /dev devtmpfs rw,nosuid,relatime,size=10240k,nr_inodes=218530,mode=755 0 0
/dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e / ext4 rw,relatime,barrier=1,data=ordered 0 0
devpts /dev/pts devpts rw,relatime,mode=600,ptmxmode=000 0 0
shm /dev/shm tmpfs rw,nosuid,nodev,relatime 0 0
/dev/sda4 /home ext4 rw,relatime,barrier=1,data=ordered 0 0
/dev/sda1 /boot ext2 rw,relatime,errors=continue 0 0

Where do they get their names form?

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#6 2010-10-07 13:12:17

karol
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Registered: 2009-05-06
Posts: 25,440

Re: [SOLVED] mtab forgets device via UUID

'/bin/findmnt --fstab' will take them from fstab. The default source is /proc/self/mountinfo.
It's in the man page.

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#7 2010-10-07 13:39:43

miro279
Member
Registered: 2010-10-02
Posts: 153

Re: [SOLVED] mtab forgets device via UUID

but thats cosmetics..

the general problem is, that there are different devices for one where it seems that the /dev/disk/by-uuid/* devices seeems to be links from the /dev/sda* devices:

ls -l /dev/sda*
brw-rw---- 1 root disk 8, 0  7. Okt 14:57 /dev/sda
brw-rw---- 1 root disk 8, 1  7. Okt 14:57 /dev/sda1
brw-rw---- 1 root disk 8, 2  7. Okt 14:57 /dev/sda2
brw-rw---- 1 root disk 8, 3  7. Okt 14:57 /dev/sda3
brw-rw---- 1 root disk 8, 4  7. Okt 14:57 /dev/sda4

and

ls -l /dev/disk/by-uuid/*
lrwxrwxrwx 1 root 0 10  7. Okt 14:57 /dev/disk/by-uuid/28955678-413a-4fd5-a459-2b129667c94e -> ../../sda2
lrwxrwxrwx 1 root 0 10  7. Okt 14:57 /dev/disk/by-uuid/8d2a1a14-7050-41d3-b7ca-f5460ab6770e -> ../../sda3
lrwxrwxrwx 1 root 0 10  7. Okt 14:57 /dev/disk/by-uuid/b3d9152c-61f2-4fb2-89d3-337ee1764b04 -> ../../sda4
lrwxrwxrwx 1 root 0 10  7. Okt 14:57 /dev/disk/by-uuid/dd98976f-fc27-4a32-8db7-d92fa36317e4 -> ../../sda1

in the one case of /dev/sda3 now the whole system thinks that it is a good idea to use the link as global reference, for the others it taks the original devices. Why?

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#8 2010-10-07 13:42:29

karol
Archivist
Registered: 2009-05-06
Posts: 25,440

Re: [SOLVED] mtab forgets device via UUID

Only the / partition is referenced by uuid.

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#9 2010-10-07 13:46:46

miro279
Member
Registered: 2010-10-02
Posts: 153

Re: [SOLVED] mtab forgets device via UUID

so the bug is, that for the / partition the link is considert reference?

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#10 2010-10-07 18:17:18

miro279
Member
Registered: 2010-10-02
Posts: 153

Re: [SOLVED] mtab forgets device via UUID

a solution for this problem is to add the Option -c to findmnt in /etc/rc.sysinit. the part that generates /etc/mtab looks like this afte that:

f [ -x /bin/findmnt -a -e /proc/self/mountinfo ]; then
        /bin/findmnt -rnuc -o SOURCE,TARGET,FSTYPE,OPTIONS >| /etc/mtab
else
        cat /proc/mounts >| /etc/mtab

I still don't understand why the / partition should be labeled different from the begining on, but Im not a expert in that of course, so there might be good reasons. How just likes to have a proper looking df command can live with that additional option I guess.

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