I'm using tape storage drive HP LTO3 1x8 auto-loader which is connected to my server running CentOS. it is detected in CentOS correctly.

cat /proc/scsi/scsi
Host: scsi2 Channel: 00 Id: 01 Lun: 00
Vendor: HP Model: 1x8 autoloader Rev: 1.50
Type: Medium Changer ANSI SCSI revision: 03

lsscsi
[1:0:0:0] cd/dvd NECVMWar VMware IDE CDR10 1.00 /dev/sr0
[2:0:0:0] disk VMware Virtual disk 1.0 /dev/sda
[2:0:1:0] mediumx HP 1x8 autoloader 1.50 /dev/sch0
But the tape device file (st* or nst*) inside the /dev directory has not been created.

I've loaded all the modules

Module Size Used by
sym53c8xx 77039 0
aic7xxx 119025 0
st 38660 0
autofs4 26888 3
sunrpc 243758 1
ipt_REJECT 2383 2
nf_conntrack_ipv4 9506 2
nf_defrag_ipv4 1483 1 nf_conntrack_ipv4
iptable_filter 2793 1
ip_tables 17831 1 iptable_filter
ip6t_REJECT 4628 2
nf_conntrack_ipv6 8748 2
nf_defrag_ipv6 12182 1 nf_conntrack_ipv6
xt_state 1492 4
nf_conntrack 79453 3 nf_conntrack_ipv4,nf_conntrack_ipv6,xt_state
ip6table_filter 2889 1
ip6_tables 19458 1 ip6table_filter
ipv6 322029 29 ip6t_REJECT,nf_conntrack_ipv6,nf_defrag_ipv6
ppdev 8729 0
parport_pc 22978 0
parport 37265 2 ppdev,parport_pc
e1000 167662 0
microcode 112594 0
vmware_balloon 7199 0
ch 13503 0
i2c_piix4 12608 0
i2c_core 31276 1 i2c_piix4
sg 30124 0
shpchp 33482 0
ext4 364410 3
mbcache 8144 1 ext4
jbd2 88738 1 ext4
sd_mod 39488 4
crc_t10dif 1541 1 sd_mod
sr_mod 16228 0
cdrom 39771 1 sr_mod
mptspi 17051 12
mptscsih 36732 1 mptspi
mptbase 93845 2 mptspi,mptscsih
scsi_transport_spi 26151 3 sym53c8xx,aic7xxx,mptspi
pata_acpi 3701 0
ata_generic 3837 0
ata_piix 22846 0
dm_mirror 14101 0
dm_region_hash 12170 1 dm_mirror
dm_log 10122 2 dm_mirror,dm_region_hash
dm_mod 81500 12 dm_mirror,dm_log

output of dmesg | grep scsi

scsi0 : ata_piix
scsi1 : ata_piix
scsi 1:0:0:0: CD-ROM NECVMWar VMware IDE CDR10 1.00 PQ: 0 ANSI: 5
scsi2 : ioc0: LSI53C1030 B0, FwRev=01032920h, Ports=1, MaxQ=128, IRQ=17
scsi 2:0:0:0: Direct-Access VMware Virtual disk 1.0 PQ: 0 ANSI: 2
scsi target2:0:0: Beginning Domain Validation
scsi target2:0:0: Domain Validation skipping write tests
scsi target2:0:0: Ending Domain Validation
scsi target2:0:0: FAST-40 WIDE SCSI 80.0 MB/s ST (25 ns, offset 127)
scsi 2:0:1:0: Medium Changer HP 1x8 autoloader 1.50 PQ: 0 ANSI: 3
scsi target2:0:1: Beginning Domain Validation
sr0: scsi3-mmc drive: 1x/1x writer dvd-ram cd/rw xa/form2 cdda tray
sr 1:0:0:0: Attached scsi CD-ROM sr0
scsi: waiting for bus probes to complete ...
scsi target2:0:1: Ending Domain Validation
scsi target2:0:1: FAST-160 WIDE SCSI 320.0 MB/s DT IU RDSTRM RTI WRFLOW PCOMP (6.25 ns,
offset 127)
sr 1:0:0:0: Attached scsi generic sg0 type 5
sd 2:0:0:0: Attached scsi generic sg1 type 0
scsi 2:0:1:0: Attached scsi generic sg2 type 8
ch 2:0:1:0: Attached scsi changer ch0

Does anyone face this issue before and find a solution?

It looks like your autochanger is being detected but not the tape drive in it.

My HP changer gives me two entries in /proc/scsi/scsi one for the changer and one for the Ultrium 4 drive in it.

Not sure on the best way to troubleshoot this but this may point you in the right direction.

@tentenths yes my tape drive is not detected....!!!!!

do you know any solution for this problem

What does /proc/devices list?

It looks like the device is recognized - sg2, and ch0

@jpollard

Output of cat /proc/devices
Character devices:
1 mem
4 /dev/vc/0
4 tty
4 ttyS
5 /dev/tty
5 /dev/console
5 /dev/ptmx
7 vcs
9 st
10 misc
13 input
21 sg
29 fb
86 ch
99 ppdev
128 ptm
136 pts
162 raw
180 usb
189 usb_device
202 cpu/msr
203 cpu/cpuid
249 hidraw
250 usbmon
251 bsg
252 pcmcia
253 watchdog
254 rtc

Block devices:
1 ramdisk
259 blkext
7 loop
8 sd
9 md
11 sr
65 sd
66 sd
67 sd
68 sd
69 sd
70 sd
71 sd
128 sd
129 sd
130 sd
131 sd
132 sd
133 sd
134 sd
135 sd
253 device-mapper
254 mdp

you are right device is recognized - sg2 and ch0
lsscsi -g
[2:0:1:0] mediumx HP 1x8 autoloader 1.50 /dev/sch0 /dev/sg2

i think some driver is missing according to me its scsi_mod
when i ran this command
# modprobe scsi_mod
FATAL: Module scsi_mod not found

From your /proc/devices, you should have a /dev/st* name. Now it is possible that udev may have altered its name, but it should show up with the device number of 9 (the entry for "9 st"). You also have the changer recorded as "86 ch", so the /dev entry with the device number 86 should also show up (again, possibly renamed by udev).

@jpollard you are right. but when i checked /dev i found nothing means there i don't fine any st* files.

That implies that udev doesn't know how to create them.

You can try a quickie test using "mknod /dev/st0 c 9 0", and see if the device responds when using /dev/st0. If you are trying the changer use "mknod /dev/ch0 c 86 0", and that should give access to it.

Now I haven't created any udev rules (never needed to) so you would have to look those up in other places, but if the devices work with the mknod then they can work with udev too.