John Kugelman's questions

/var/log/lastlog gets written to when you log in. The size of this file is based off of the largest UID in the system. The larger the maximum UID, the larger this file is. Thankfully it's a sparse file so the size on disk is much smaller than the size ls reports (ls -s reports the size on disk).

On our system we're authenticating against an Active Directory server, and the UIDs users are assigned end up being really, really large. Like, say, UID 900,000,000 for the first AD user, 900,000,001 for the second, etc.

That's strange but should be okay. It results in /var/log/lastlog being huuuuuge, though--once an AD user logs in lastlog shows up as 280GB. Its real size is still small, thankfully.

This works fine when /var/log/lastlog is stored on the hard drive on an ext3 filesystem. It breaks, however, if lastlog is stored in a tmpfs filesystem. Then it appears that the max file size for any file on the tmpfs is 256GB, so the sessreg program errors out trying to write to lastlog.

Where is this 256GB limit coming from, and how can I increase it?

As a simple test for creating large sparse files I've been doing:

dd if=/dev/zero of=sparse-file bs=1 count=1 seek=300GB

I've tried Googling for "tmpfs max file size", "256GB filesystem limit", "linux max file size", things like that. I haven't been able to find much. The only mention of 256GB I can find is that ext3 filesystems with 2KB blocks are limited to 256GB files. But our hard drives are formatted with 4K blocks so that doesn't seem to be it--not to mention this is happening in a tmpfs mounted ON TOP of the hard drive so the ext3 partition shouldn't be a factor.

This is all happening on a 64-bit Red Hat Enterprise Linux 5.4 system. Interestingly, on my personal development machine, which is a 32-bit Fedora Core 6 box, I can create 300GB+ files in tmpfs filesystems no problem. On the RHEL5.4 systems it is no go.

Is there a tool or way to figure out what file/files are on a specific sector of a DVD?

Sometimes when installing from DVD+R's/DVD-R's I get a "Buffer I/O error" message with a sector number of range of sectors listed in the message. Is there a way to figure out the specific files that are affected? I do have the original .iso images from which these discs were created.

Edit: See my previous question for details on the Buffer I/O error. If you have any ideas about that please post there. For this question let's ignore why my DVDs are bad. :-)

We've had a problem occur when writing to DVD+Rs and DVD-Rs using growisofs on Redhat Enterprise Linux 5.0. What we’re trying to do is backup audit data that we've stored, which is basically one .zip file for each day's worth of audit data. The .zip files are relatively small, generally only a few megabytes each. We receive the following error message from growisofs when writing to a DVD+R or DVD-R:

:-( unable to pread64(2) primary volume descriptor: Input/output error
you most likely want to use -Z option.

growisofs also exits with an exit code of 150. According to a Debian mailing list post I read (link no longer working) growisofs returns errno+128, so this appears to correspond with errno=22, which is EINVAL (Invalid argument).

The primary volume descriptor is definitely there as we have already initialized the DVD with -Z. The first thing we do is growisofs -Z, followed by one growisofs -M command per file. The error usually happens on the second file we write--i.e., the DVD is initialized with -Z, we write one .zip file successfully, and then the second .zip file yields this error message.

A simple workaround is to physically eject the DVD and then re-insert it at which point the DVD works again and we are able to write the rest of the files. That's less than ideal, though. The error is not consistent but it is quite frequent and ejecting seems to always fix the problem.

Here are the commands we use to write to the DVD:

growisofs -Z /dev/dvd -rJ -use-the-force-luke=notray blank.iso

for each FILE:
    growisofs -M /dev/dvd -rJ -use-the-force-luke=notray "$FILE"

Here's sample output from dvd+rw-mediainfo /dev/dvd, if it helps:

INQUIRY:                [TEAC    ][DV-W28EC        ][1.0B]
GET [CURRENT] CONFIGURATION:
 Mounted Media:         1Bh, DVD+R
 Media ID:              RITEK/F16
 Current Write Speed:   8.0x1385=11080KB/s
 Write Speed #0:        8.0x1385=11080KB/s
 Write Speed #1:        6.0x1385=8310KB/s
 Write Speed #2:        4.0x1385=5540KB/s
 Write Speed #3:        2.4x1385=3324KB/s
 Speed Descriptor#0:    00/2295103 [email protected]=11080KB/s [email protected]=11080KB/s
 Speed Descriptor#1:    00/2295103 [email protected]=8310KB/s [email protected]=8310KB/s
 Speed Descriptor#2:    00/2295103 [email protected]=5540KB/s [email protected]=5540KB/s
 Speed Descriptor#3:    00/2295103 [email protected]=3324KB/s [email protected]=3324KB/s
READ DVD STRUCTURE[#0h]:
 Media Book Type:       00h, DVD-ROM book [revision 0]
 Legacy lead-out at:    2295104*2KB=4700372992
READ DISC INFORMATION:
 Disc status:           appendable
 Number of Sessions:    21
 State of Last Session: empty
 "Next" Track:          21
 Number of Tracks:      21

Any ideas on what is causing this problem or how to fix it?