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Protecting a Second Hard Drive from autoinstall

Best of Technical Support


Issue #88, August 2001

Our experts answer your technical questions.

Copying Old Tapes

Before I came to my current job, the archive system was sporadic at best, using multiple media formats from DAT to Exabyte. I have been given the task of copying all these formats to a single standard (in this case AIT). I am trying to copy one tape to another and cannot find a proper command. We are using the GNU version of tar and would like to keep this standard. I have tried

dd if=/dev/<device file> of=/dev/<device file2>

and cannot even get the command to read the tape. —Charles Long, charlesl@wildbrain.com

The command you are using looks correct, the only missing item may be a block size (bs) in case the format of the tapes was written with a specific block size factor (that you have to find out). Then the command will be

dd if=/dev/XXXX of=/dev/YYYY bs=<your_block_size_number>

—Felipe E. Barousse Boué, fbarousse@piensa.com

dd should read a tape, regardless of the program used to write the tape (e.g., tar, dump, NetBackup). The problem could be one of the following: 1) tape is written on a different/incompatible drive, 2) tape is faulty, 3) heads on drive are dirty or 4) the header on the tape. So skip before reading (use mt fsf and no-rewind device) and try reading the tape(s) with the original program in read-only mode to make sure the tape(s) and drive(s) are working correctly. If you cannot read the tapes in any way, then the backups are useless. —Keith Trollope, keith@wishing-well.demon.co.uk

Protecting a Second Hard Drive from autoinstall

I want to install Red Hat 7.1 on only my master disk. I have a slave drive with Win98 installed at present. The master disk is empty, so I’m not trying to dual boot my PC in that sense. Short of physically disconnecting it, is there a way to autopartition the one disk? How would you recommend I divide up my 40GB disk? —Paul Henman, linuxj@henman.ca

Red Hat definitely lets you partition the drives as you wish. I usually recommend the following: / 100MB /safe 100MB /usr 3-4G in your case, more if you want /var everything else

You need to symlink /tmp to /var/tmp/tmp and /home to /var/home. The advantage of this scheme is that your root partition is critical, so if you keep it small, you reduce the changes of corruption, and you can keep an on-line backup copy of it in /safe. —Marc Merlin, marc_bts@valinux.com

Starting X from a Bootdisk

I had installed SuSE 6.3 on an extreme partition of my HDD (so no LILO). I later created a bootdisk from the CD through the rawrite utility. I am able to access the command-line interface by booting from the floppy and specifying the installed partition. Can I initiate the GUI interface in any way? —Manoj Ramakrishnan, mark2gp@sify.com

There are different ways to initiate the GUI interface. You can directly start X from the command line with startx. You can start xdm, kdm or gdm as root; they often have an init script in /etc/init.d/, or they can be started from the command line. The last and probably easiest option is to set the right runlevel, 3, in YaST2. —Marc Merlin, marc_bts@valinux.com

Setting the Bytes per Inode

I would like to know how to set the inode size for my entire hard drive, each partition. Is there a way I can set the inode size during Red Hat 7.0’s installation, or do I have to use debugfs to change inode sizes? —Matt Walters, matt.walters@syberos.com

You cannot change the bytes per inode after the filesystem has been created. If you want to set it when you install Red Hat, you can drop to the shell (F2 from the text-mode installer) and create the filesystems yourself. After that, you can return to the installer, which has the option of not formatting partitions. A sample command would be:

mke2fs -s 1 -b 4096 -i 8192 -m 1 /dev/sda1

where -s 1 parses superblocks (Linux 2.2 or better), -b 4096 sets the disk block size to 4K, -i 8192 sets bytes per inode to 8K and -m 1 sets reserved block size to 1% of your partition size (appropriate for today’s big disks and partitions). —Marc Merlin, marc_bts@valinux.com

I Have No /dev/cdrom and I Must Mount

I erased my /dev/cdrom by mistake and I can’t do mkdir to replace it because it must be a block mode file. Do you know how I can remount my CD-ROM? —Yves, cloude7@hotmail.com

/dev/cdrom is usually a symbolic link to one of the disk drives detected at boot. Find the device for the CD-ROM with dmesg | grep CDROM (e.g., mine says hdc: YAMAHA CRW8424E, ATAPI CDROM drive). Then create the link with cd /dev ln -s hdc cdrom. However, if you are using an IDE CD-W, then it will be something like cd /dev ln -s scd0 cdrom rather than hdc. —Keith Trollope, keith@wishing-well.demon.co.uk


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