Device functionality is encoded in the “Minor number” of device nodes in /dev.
TMSCP Tapes:
This is valid for my TU81+ tape drive.
According to /sys/pdpuba/tm.c, these bits in the minor number modify the tapes behaviour.
Bit 1,0 (mask 0x03): device number 0..3 (by default, only 2 tapes are compiled into the kernel)
Bit 2: (mask 0x04): no rewind flag
Bits 4,3 (mask 0x18): density 0..3: 800, 1600, 6250, not used
For device #0, these are the minor numbers for certain functions:
|
The “rewind” device nodes are “mt
I found this in tmscp.c”: Density may only changed at BOT (begin of tape)”
To generate devices nodes for TU81 TMSCP tape drive::
cd /dev
rm mt* rmt* nmt* nrmt*
./MAKEDEV tu0
Test:
1. Copy 1 file to tape (test file is the system: “/unix”
# mt rew
# dd if=/unix of=/dev/rmt12 bs=10240
2. Read in with other name “/tstunix”:
# mt rew
# dd if=/dev/rmt12 of=/tstunix bs=10240
3. check, wether restore = original
# diff unix tstunix
Dump and restore:
- use “raw device “rmt*”, not “mt”
- use blocksize bs=10240
* Calc size of dump:
tar cf - | wc -c *
tar cfv - | dd of=/dev/rmt12 bs=10240
* Check archive content
dd if=/dev/rmt12 bs=10240 | tar tvf -
* Restore files
dd if=/dev/rmt12 bs=10240 | tar xvf -
TU81+ chache:
Normal: enable TU81+ cache with:
# mt cacheon
Anomalies detected: Verify writing: must cache be flushed????
In tmscp-c steht:
“Enable cache with "sysctl -w machdep.tmscp.cache=0xXXXX".
xxxx =00001 = firstdrive on first ctl
sysctl -w machdep.tmscp.cache=1