The easiest way is to obtain a Slackware kernel from your nearest Slackware mirror site. Slackware kernels are generic kernels which atttempt to include drivers for as many devices as possible, so if you have a SCSI or IDE controller, chances are that a driver for it is included in the Slackware kernel.
Go to the a1 directory and select either IDE or SCSI kernel depending on the type of controller you have. Check the xxxxkern.cfg file for the selected kernel to see the drivers which have been included in that kernel. If the device you want is in that list, then the corresponding kernel should boot your computer. Download the xxxxkern.tgz file and copy it to your boot diskette as described above in the section on making boot disks.
You must then check the root device in the kernel, using the rdev command:
rdev zImage
Rdev will then display the current root device in the kernel. If this is not the same as the root device you want, then use rdev to change it. For example, the kernel I tried was set to /dev/sda2, but my root scsi partition is /dev/sda8. To use a root diskette, you would have to use the command:
rdev zImage /dev/fd0
If you want to know how to set up a Slackware root disk as well, that's outside the scope of this HOWTO, so I suggest you check the Linux Install Guide or get the Slackware distribution. See the section in this HOWTO titled "References".
Just copy the kernel to your boot diskette using the dd command for a boot diskette without a filesystem, or the cp command for a boot/root disk. Refer to the section in this HOWTO titled "Boot" for details on creating a boot disk. The description applies equally to updating a kernel on a boot disk.
This is not really a Bootdisk topic, but it is asked so often, so: the answer is, use the DOS command:
FDISK /MBR
MBR stands for Master Boot Record, and it replaces the boot sector with a clean DOS one, without affecting the partition table. Some purists disagree with this, but even the author of LILO, Werner Almesberger, suggests it. It is easy, and it works.
You can also use the dd command to copy the backup saved by LILO to the boot sector - refer to the LILO documentation if you wish to do this.
If you don't have a boot disk standing by, then probably the easiest method is to obtain a Slackware kernel for your disk controller type (IDE or SCSI) as described above for "How do I make a boot disk with a XXX driver?". You can then boot your computer using this kernel, then repair whatever damage there is.
The kernel you get may not have the root device set to the disk type and partition you want. For example, Slackware's generic scsi kernel has the root device set to /dev/sda2, whereas my root Linux partition happens to be /dev/sda8. In this case the root device in the kernel will have to be changed.
You can still change the root device and ramdisk settings in the kernel even if all you have is a kernel, and some other operating system, such as DOS.
Rdev changes kernel settings by changing the values at fixed offsets in the kernel file, so you can do the same if you have a hex editor available on whatever systems you do still have running - for example, Norton Utilities Disk Editor under DOS. You then need to check and if necessary change the values in the kernel at the following offsets:
0x01F8 Low byte of RAMDISK size
0x01F9 High byte of RAMDISK size
0x01FC Root minor device number - see below
0X01FD Root major device number - see below
The ramdisk size is the number of blocks of ramdisk to create. If you want to boot from a root diskette then set this to decimal 1440, which is 0x05A0, thus set offset 0x01F8 to 0xA0 and offset 0x01F9 to 0x05. This will allocate enough space for a 1.4Mb diskette.
The major and minor device numbers must be set to the device you want to mount your root filesystem on. Some useful values to select from are:
device major minor
/dev/fd0 2 0 1st floppy drive
/dev/hda1 3 1 partition 1 on 1st IDE drive
/dev/sda1 8 1 partition 1 on 1st scsi drive
/dev/sda8 8 8 partition 8 on 1st scsi drive
Once you have set these values then you can write the file to a diskette using either Norton Utilities Disk Editor, or a program called rawrite.exe. This program is included in several distributions, including the SLS and Slackware distributions. It is a DOS program which writes a file to the "raw" disk, starting at the boot sector, instead of writing it to the file system. If you use Norton Utilities, then you must write the file to a physical disk starting at the beginning of the disk.
It is never desirable to have just one set of rescue disks - 2 or 3 should be kept in case one is unreadable.
The easiest way of making copies of any diskettes, including bootable and utility diskettes, is to use the dd command to copy the contents of the original diskette to a file on your hard drive, and then use the same command to copy the file back to a new diskette. Note that you do not need to, and should not, mount the diskettes, because dd uses the raw device interface.
To copy the original, enter the command:
dd if=devicename of=filename
where devicename the device name of the diskette
drive
and filename the name of the file where you
want to copy to
For example, to copy from /dev/fd0 to a temporary file called /tmp/diskette.copy, I would enter the command:
dd if=/dev/fd0 of=/tmp/diskette.copy
Omitting the "count" parameter, as we have done here, means that the whole diskette of 2880 (for a high-density) blocks will be copied.
To copy the resulting file back to a new diskette, insert the new diskette and enter the reverse command:
dd if=filename of=devicename
Note that the above discussion assumes that you have only one diskette drive. If you have two of the same type, then you can copy diskettes using a command like:
dd if=/dev/fd0 of=/dev/fd1
Where a disk device cannot be autodetected it is necessary to supply the kernel with a command device parameter string, such as:
aha152x=0x340,11,3,1
For example, a sample command line using the above parameter string would be:
zImage aha152x=0x340,11,3,1 root=/dev/sda1 lock
A sample APPEND statement is:
APPEND = "aha152x=0x340,11,3,1"
Note that the parameter string must NOT be enclosed in quotes on the command line, but it MUST be enclosed in quotes in the APPEND statement.
Note also that for the parameter string to be acted on, the kernel must contain the driver for that disk type. If it does not, then there is nothing listening for the parameter string, and you will have to rebuild the kernel to include the required driver. For details on rebuilding the kernel, cd to /usr/src/linux and read the README, and read the Linux FAQ and Installation HOWTO. Alternatively you could obtain a generic kernel for the disk type and install that.
Readers are strongly urged to read the LILO documentation before experimenting with LILO installation. Incautious use of the "BOOT" statement can damage partitions.
The following instructions apply to kernels earlier than 1.3.48. For kernels 1.3.48+, it is best to create a compressed filesystem as described in Section 7.
An oversize ramdisk filesystem is a filesystem in a ramdisk larger than the size of the root disk it was loaded from. This can be extremely useful when using Ftape, which requires exclusive use of the floppy disk controller (see the Ftape HOWTO for details.)
Two things are required: create an oversize file system on the root diskette, and then patch the kernel so that it will not try to load blocks off the end of the diskette.
To create an oversize filesystem, two methods are possible:
mke2fs /dev/fd0 3000
dd if=/dev/hdb of=/dev/fd0 bs=1024 count=1440
dd if=/dev/hdb of=tailpart bs=1024 skip=1440
cmp -l tailparm /dev/zero
The second thing required to get an oversized filesystem is to get the kernel to stop loading at the end of the physical diskette when it tries to load the root diskette into ramdisk. To do this, a simple patch can be applied to the ramdisk driver, which should be found in /usr/src/linux/drivers/block/ramdisk.c. The following patch has been contributed by Bruce Elliot. It is for kernel version 1.2.0, but it should be fairly easy to apply to later versions. Even if the patch will not apply, the code is not complex, so the patch could easily be modified until it worked.
=================================================================
X--- ramdisk.c~ Mon Jan 23 13:04:09 1995
X+++ ramdisk.c Mon May 29 00:54:52 1995
X@@ -113,6 +113,7 @@
X (struct ext2_super_block *)&sb;
X int block, tries;
X int i = 1;
X+ int fblocks;
X int nblocks;
X char *cp;
X
X@@ -168,12 +169,16 @@
X nblocks, rd_length >> BLOCK_SIZE_BITS);
X return;
X }
X- printk("RAMDISK: Loading %d blocks into RAM disk", nblocks);
X+ fblocks = blk_size[MAJOR(ROOT_DEV)][MINOR(ROOT_DEV)];
X+ if (fblocks > nblocks)
X+ fblocks = nblocks;
X+ printk("RAMDISK: Loading %d blocks into %d block filesystem "
X+ "in RAM disk", fblocks, nblocks);
X
X /* We found an image file system. Load it into core! */
X cp = rd_start;
X- while (nblocks) {
X- if (nblocks > 2)
X+ while (fblocks) {
X+ if (fblocks > 2)
X bh = breada(ROOT_DEV, block, BLOCK_SIZE, 0, PAGE_SIZE);
X else
X bh = bread(ROOT_DEV, block, BLOCK_SIZE);
X@@ -184,7 +189,7 @@
X }
X (void) memcpy(cp, bh->b_data, BLOCK_SIZE);
X brelse(bh);
X- if (!(nblocks-- & 15)) printk(".");
X+ if (!(fblocks-- & 15)) printk(".");
X cp += BLOCK_SIZE;
X block++;
X i++;
=================================================================
Some warnings: I have been able to create stable ramdisk filesystems in this fashion of 3500 blocks, but if I try 3600 or more then the kernel collapses with an error something like "fixup table corrupt". I have not been able to track down why, but obviously something is overflowing. Up to 3500 blocks, though, I have had no problems.
A: cannot execute B. Why?There are several cases of program names being hardcoded in various utilities. These cases do not occur everywhere, but they may explain why an executable apparently cannot be found on your system even though you can see that it is there. You can find out if a given program has the name of another hardcoded by using the "strings" command and piping the output through grep.
Known examples of hardcoding are:
/etc/reboot hardcoded, so
reboot must be placed in the /etc directory./etc/rc.d
files as they appear on your hard disk.