fdformat except as root ?
/proc/kcore ! Can I delete it ?
SCSI disks are accessed by linear block numbers; the BIOS invents some `logical' cylinders/heads/sectors fiction to support DOS.
DOS will usually not be able to access partitions which extend beyond 1024 logical cylinders, and will make booting a Linux kernel from such partitions using LILO problematic at best.
You can still use such partitions for Linux or other operating systems that access the controller directly.
I'd recommend creating at least one Linux partition entirely under the
1024-logical-cylinder limit and booting off that; the other
partitions will then be OK.
Question 4.2. How can I undelete files ?
In general, this is very hard to do on Unices because of their
multitasking nature. Undelete functionality for the ext2fs is being
worked on, but don't hold your breath.
There are a number of packages available that work by providing new commands for deletion and sometimes copying that move deleted files into a `wastebasket' directory instead; they can then be recovered until cleaned out automatically by background processing.
Alternatively you can search the raw disk device which holds the
filesystem in question. This is hard work, and you will need to be
root to do this.
Question 4.3. Is there a defragmenter for ext2fs etc.
?
Yes. There is a Linux filesystem defragmenter for ext2, minix and
old-style ext filesystems available on sunsite.unc.edu in system/Filesystems/defrag-0.6.tar.gz.
Users of the ext2 filesystem can probably do without defrag since ext2
contains extra code to keep fragmentation reduced even in very full
filesystems.
Question 4.4. How do I format and create a filesystem on a floppy
?
For a 3.5 inch high density floppy:
fdformat /dev/fd0H1440 mkfs -t ext2 -m 0 /dev/fd0H1440 1440For a 5.25 inch floppy use
fd0h1200 and 1200 as appropriate. For the `B' drive use fd1 instead of fd0. Full details of which floppy devices do what can be found in the Linux Device List
[Q2.1 `Where can I get the HOWTOs and other documentation
?']. You may have to run mke2fs directly instead of mkfs -t ext2. The -m 0 option tells mkfs.ext2 not to reserve any space on the disk for the superuser ---
usually the last 10% is reserved for root.
The first command low-level formats the floppy; the second creates an
empty filesystem on it. After doing this you can mount the floppy
like a hard disk partition and simply cp and mv files, etc.
Question 4.5. I get nasty messages about inodes, blocks, and the
suchlike
You probably have a corrupted filesystem, probably caused by not
shutting Linux down properly before turning off the power or
resetting. You need to use a recent shutdown program to do this --- for example, the one included in the util-linux package, available
on sunsite and tsx-11.
If you're lucky the program fsck (or e2fsck or xfsck as appropriate if you don't have the automatic
fsck front-end) will be able to repair your filesystem; if you're unlucky the filesystem is
trashed and you'll have to reinitialise it with
mkfs (or mke2fs, mkxfs etc.) it and restore from a backup.
NB: don't try to check a filesystem that's mounted read-write - this includes the root partition if you don't see
VFS: mounted root ... read-onlyat boot time.
Adding Swap: NNNNk swap-space
If you don't see any messages at all you are probably missing
swapon -av (the command to enable swapping) in your
/etc/rc.local or /etc/rc.d/* (the system startup scripts), or have forgotten to make the right entry in
/etc/fstab:
/dev/hda2 none swap sw
for example.
If you see
Unable to find swap-space signature
you have forgotten to run mkswap. See the manpage for details; it works much like mkfs.
Check the Installation HOWTO for detailed instructions of how to set up a swap area.
Question 4.7. How do I remove LILO so my system boots DOS again
?
Using DOS (MS-DOS 5.0 or later, or OS/2), type
FDISK /MBR (which is not documented). This will restore a standard MS-DOS Master
Boot Record. If you have DR-DOS 6.0, go into
FDISK in the normal way and then select the `Re-write Master Boot Record' option.
If you don't have DOS 5 or DR-DOS you need to have the boot sector
that LILO saved when you first installed it. You did keep that file,
didn't you ? It's probably called boot.0301 or some such. Type
dd if=boot.0301 of=/dev/hda bs=445 count=1(or
sda if you're using a SCSI disk). This may also wipe out
your partition table, so beware ! If you're desperate, you could use
dd if=/dev/zero of=/dev/hda bs=512 count=1which will erase your partition table and boot sector completely: you can then reformat the disk using your favourite software; however this will render the contents of your disk inaccessible --- you'll lose it all unless you're an expert.
Note that the DOS MBR boots whichever (single!) partition is flagged
as `active'; you may need to use fdisk to set and clear the active
flags on partitions appropriately.
Question 4.8. Why can't I use
The system call to format a floppy may only be done as root,
regardless of the permissions of fdformat except as root ?
/dev/fd0*. If you want any user to be able to format a floppy try getting the
fdformat2 program; this works around the problems by being setuid to root.
Question 4.9. Is there something like Stacker or Doublespace for
Linux ?
Currently none of the Linux filesystems can do compression in the
filesystem.
There is a program called Zlibc which allows existing applications to
read compressed (GNU zipped) files as if they were not compressed.
After installing it you can compress files using
gzip and programs will still find them, without having to change the programs. Look on
sunsite.unc.edu in /pub/Linux/libs. The author is Alain.Knaff@imag.fr.
There is a compressing block device driver that can provide
filesystem-independant on the fly disk compression in the kernel. It
is called `DouBle'. There is a source only distribution on
sunsite.unc.edu in /pub/Linux/kernel/patches/diskdrives; the author is Jean-Marc Verbavatz jmv@receptor.mgh.harvard.edu. Note that since this compresses inodes (administrative information)
and directories as well as file contents any corruption is quite
likely to be serious.
There is also a package available called
tcx (Transparently Compressed Executables) which allows you to keep infrequently used
executables compressed and only uncompress them temporarily while you
use them. You'll find it on the Linux FTP sites
[Q2.5 `Where can I get Linux material by FTP ?']; it was also announced in comp.os.linux.announce. Note - this is not the same as gzexe, which is an inferior implementation of
the same concept.
Question 4.10. My ext2fs partitions are checked each time I
reboot.
See Q9.12 `EXT2-fs: warning: mounting unchecked filesystem'.
Question 4.11. My root filesystem is read-only
!
Remount it. If /etc/fstab is correct you can simply mount -n -o remount /. If /etc/fstab is wrong you must give the device name and posibly the type too: e.g.
mount -n -o remount -t ext2 /dev/hda2 /. To understand why you got into this state see Q9.12 `EXT2-fs: warning: mounting unchecked filesystem'.
Question 4.12. I have a huge
None of the files in /proc/kcore ! Can I delete it ?
/proc are really there - they're all "pretend" files made up by the kernel, to give you
information about the system, and don't take up any hard disk space.
/proc/kcore is like an "alias" for the memory in your computer;
its size is the same as the amount of RAM you have, and if you ask to
read it as a file the kernel does memory reads.
Question 4.13. My AHA1542C doesn't work with
Linux.
The option to allow disks with more than 1024 cylinders is only
required as a workaround for a DOS misfeature and should be turned
off under Linux. For older Linux kernels you need to turn
off most of the "advanced BIOS" options - all but the one
about scanning the bus for bootable devices.
Ian Jackson / ijackson@gnu.ai.mit.edu - 06 March 1996