[SOLVED] external hard disk fails to show up on bootin/re-booting my system sometimes

nitecrawler · 08-04-2015, 04:52 AM

hi all

here is an issue i face....

some days when i restart my slackware, i see that my external hard disk fails to boot up or show in the mount point i had set it to...hence, my external hard disk becomes unavailable to use during the session...need a restart again to show it come up....

yesterday, i did a dmesg log check on it when it didnt come up and then later restarted to check dmesg again...and here is one line i found missing when it didnt show up...

a line which maps sdb to sdb1 thats my device right there in my /etc/fstab as i had set it earlier...
precisely, [sdb]:[sdb1] //missing when the external hard disk doesnt show up

in both boot cases ie when EHD(external hard disk) not showing and showing, the HD is detected with details except this critical matching line not performed...

Didier Spaier · 08-04-2015, 05:30 AM

Name your external hard disk's partition by its UUID instead of /dev/sd<something> in the first field of /etc/fstab, see "man fstab"

To know its UUID, with the hard disk plugged in type

Code:

lsblk -o model,name,fstype,size,uuid

nitecrawler · 08-04-2015, 06:40 AM

thanks didier...

quoting from manpages:

Quote:

Instead of giving the device explicitly, one may indicate the (ext2 or xfs) filesystem that is to be mounted by its UUID or volume label (cf. e2label(8) or xfs_admin(8)), writing LABEL=<label> or UUID=<uuid>, e.g., 'LABEL=Boot' or 'UUID=3e6be9de-8139-11d1-9106-a43f08d823a6'. This will make the system more robust: adding or removing a SCSI disk changes the disk device name but not the filesystem volume label

its mentioned there too....
i am just curious how the disk device name changes on adding or removing...so does it mean sdb could change to something else or is it sdb1 may change to sdb2 etc?

Didier Spaier · 08-04-2015, 11:44 AM

Quote:

Originally Posted by nitecrawler

i am just curious how the disk device name changes on adding or removing...so does it mean sdb could change to something else or is it sdb1 may change to sdb2 etc?

That's actually the name of the SCSI disk that change. This can happen for instance if you plug in an USB stick before your external hard disk. If the USB stick has been found first by the kernel it will be called sdb, then the external hard disk sdc, etc. You can check that easily yourself. But the partitions will keep their numbers, e.g. the one that you knew as /dev/sb1 could be named /dev/sdc1 or /dev/sdd1, but not /dev/sdc2 or /dev/sdd2.

nitecrawler · 08-04-2015, 12:03 PM

cool info...perfect....thanks...its resolved....