Hello everyone . there are four hard disks installed : 1 ) / dev / sda ( divided into / dev / sda1 - Windows7 , / dev / sda2 - Slackware 64 Linux ( / ) , / dev / sda3 - Linux ( / slackware-home ) ) 2 ) / dev / sdb ( divided into / dev / sdb1 ( / ) - arch linux , / dev / sdb2 - home of arch linux ( / home ) , / dev / sdb3 swap ) , 3 ) / dev / sdc ( divided into / dev /sdc1- slackware 64 14.1 linux ( / ) , / dev / sdc2 - linux ( / home ) ) , and 4 ) / dev / sdd ( divided into / dev / sdd1 - slackware64 14.1 linux ( / ) and / dev / sdd2 linux ( / home ) .

The other disks , / dev / sde and / dev / sdf are external usb hd .

the problem is that the system of the arch linux (that is installed on /dev/sdb) is confusing everything . the partitions related to the hard disk / dev / sdb sometimes appear as / dev / sda and / dev / sda as / dev / sdb . sometimes the system recognizes the swap partition ( which in reality is in / dev / sdb3 ) as if it were in / dev / sdc3 . so if I try to start the system and enter the Graphical on arch linux it is warned that there is no / home ( or not found ) .it seems that this happening as a result of the mess the arch system is doing .

This all started after / dev / sdd was installed (the fourth hard disk) .

I cannot understand what is happening.

I removed /dev/sdd and the arch system returne do normal situation. So I thought that was a hardware issue and that I had found the solution. But when I reinstalled /dev/sdd hard disk again the arch system starting mixing everything again...the /dev/sb1 where the arch system is installed is recognized by /dev/sdc1... the arch system, I do not know why sees its partition like /dev/sdc1 not like /dev/sdb1..

I must remark that everything is perfect with slackware linux that is in the other partitions...

thanks and sorry for the long post but I tried my best to be understood

There is no assurance about the order in which drives are detected. That is why it is best to refer to partitions by LABEL or UUID, or, if that is not possible, by their entry in /dev/disk/by-id/, where the names include drive serial numbers. One of the few times you need to resort to that last option is for an encrypted swap partition, which has no usable identification unless the drive is partitioned with GPT.

Thanks rknichols
I have already done it. Fstab file is based on UUID for all the partitions.Nevertheless,the arch system insistis on recognizing /dev/sdb1(where the arch system is installed) as /dev/sdc1.
The only way it recognizes the partitions correctly is by removing /dev/sdd the fourth hd.
Besides, I gave up the arch grub and I am using now the grub of another distribution (the one which is on /dev/sda2).
So, by using this grub menu, I can initialize all the distros ( the ones that are on/dev/sda2; on /dev/sdc1; and on /dev/sdd1) except the arch linux (/dev/sdb1) because its system insists on recognizing the arch partition as /dev/sdc1 instead of /dev/sdb1.
so I reach the conclusion this is an arch system problem...and the solution seems to be hard...

solved: I have finally found the solution -

and the solution revealed to be easier than I had imagined just changed to fstab options to "defaults" and voilá...no problem anymore to initialize arch linux ...the arch system still recognizes the partition and hd where it is installed as /dev/sdc1 and not as /dev/sdb1 but this does not prevent the arch system from booting...I also removed from fstab the entries concerced to the usb external hd...also, the fstab file system reference is by UUID...below is the entries concerned to arch (/ and /home)...I must remark that I am not using arch grub (in /dev/sdb1) anymore. Now I am using the grub of another distro that is in /dev/sda2...I do not know if I apply the changes to arch grub and uses it again I will be able to initialize not only the arch partition but also all the other partitions. I think so, as I use UUID...but for now I have the solution...I can try using again arch grub later with the changes I have made...thank you enormously for your attention