$ binwalk -e linux_image.img
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
0 0x0 Android bootimg, kernel size: 6897653 bytes, kernel addr: 0x81C08000, ramdisk size: 5959520 bytes, ramdisk addr: 0x81C08000, product name: ""
2048 0x800 Linux kernel ARM boot executable zImage (little-endian)
18479 0x482F gzip compressed data, maximum compression, from Unix, last modified: 1970-01-01 00:00:00 (null date)
6761720 0x672CF8 device tree image (dtb)
6883304 0x6907E8 Unix path: /dev/block/platform/soc/7824900.sdhci/by-name/vendor
6899712 0x694800 gzip compressed data, maximum compression, has original file name: "rootfs.cpio", from Unix, last modified: 2019-04-06 00:42:26
9706949 0x941DC5 MySQL ISAM compressed data file Version 11
$ dd if=linux_image.img of=vmlinuz bs=1 skip=2048 count=6897653
$ file vmlinuz
vmlinuz: Linux kernel ARM boot executable zImage (little-endian)
$ dd if=vmlinuz bs=1 skip=$(LC_ALL=C grep -a -b -o $'\x1f\x8b\x08\x00\x00\x00\x00\x00' vmlinuz-3.18.66-perf | head -n 1 | cut -d ':' -f 1) | zcat | grep -a 'Linux version'
Linux version 3.18.66 (build#test) (gcc version 4.9.3 (GCC) ) #1 SMP PREEMPT Fri Apr 1 13:16:33 PDT 2018
Running 'qemu-system-arm.exe -machine vexpress-a9 -cpu cortex-a7 -smp 4 -kernel vmlinuz' blank screen
If you pull a random Arm Linux kernel (including Android) from somewhere and try to run it on anything other than the hardware that it is intended to boot on, the expected result is that it crashes very early in bootup without being able to output anything to screen or serial port, ie you get a black screen and nothing happens. The most likely situation here is that your image is fine and not corrupt, it's just not built to run on the vexpress-a9 board you're running it on.
In the unlikely event that this really is a kernel built for the vexpress-a9, the next problem you have is that you haven't passed QEMU a device tree blob via the -dtb option. Modern Linux kernels don't hardcode all the information about the boards they can run on, but instead expect the bootloader (which is QEMU in this case) to pass them a data file which provides information about where all the devices are for the board. If you don't do that, then the result is the same as above: kernel crashes very early in bootup without being able to output any information, so black screen.
I want to limit the maximum memory a process can you in Centos. There can be scenarios where a process ends up using all of the available memory or most of the memory affecting other processes in the system. Therefore, I want to know how this can be limited.
Also, if you can give a sample program where you are limiting the memory usage of a process and show the following scenarios that would be helpful.
Memory allocation successful when requested memory within the set limits.
Memory allocation failed when requested memory above the set limits.
-Thanks
ulimit can be used to limit memory utilization (among other things)
Here is an example of setting memory usage so low that /bin/ls (which is larger than /bin/cat) no longer works, but /bin/cat still works.
$ ls -lh /bin/ls /bin/cat
-rwxr-xr-x 1 root root 25K May 24 2008 /bin/cat
-rwxr-xr-x 1 root root 88K May 24 2008 /bin/ls
$ date > test.txt
$ ulimit -d 10000 -m 10000 -v 10000
$ /bin/ls date.txt
/bin/ls: error while loading shared libraries: libc.so.6: failed to map segment from shared object: Cannot allocate memory
$ /bin/cat date.txt
Thu Mar 26 11:51:16 PDT 2009
$
Note: If I set the limits to 1000 kilobytes, neither program works, because they load libraries, which increase their size. above 1000 KB.
-d data segment size
-m max memory size
-v virtual memory size
Run ulimit -a to see all the resource caps ulimits can set.
I was looking for a way to find out where my program spends time. I read the perf tutorial and tried to profile sleep times as it is described there. I wrote the simplest possible program to profile:
#include <unistd.h>
int main() {
sleep(10);
return 0;
}
then I executed it with perf:
$ sudo perf record -e sched:sched_stat_sleep -e sched:sched_switch -e sched:sched_process_exit -g -o ~/perf.data.raw ./a.out
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.013 MB /home/pablo/perf.data.raw (~578 samples) ]
$ sudo perf inject -v -s -i ~/perf.data.raw -o ~/perf.data
build id event received for [kernel.kallsyms]: d62870685909222126e7070d2bafdf029f7ed3b6
failed to write feature 2
$ sudo perf report --stdio --show-total-period -i ~/perf.data
Error:
The /home/pablo/perf.data file has no samples!
Does anybody know how to avoid these errors? What do they mean? failed to write feature 2 doesn't look too user-friendly...
Update:
$ uname -a
Linux debian 3.12-1-amd64 #1 SMP Debian 3.12.9-1 (2014-02-01) x86_64 GNU/Linux
There is a error message from your second perf command from https://perf.wiki.kernel.org/index.php/Tutorial#Profiling_sleep_times - perf inject -s
$ sudo perf inject -v -s -i ~/perf.data.raw -o ~/perf.data
build id event received for [kernel.kallsyms]: d62870685909222126e7070d2bafdf029f7ed3b6
failed to write feature 2
failed to write feature 2 doesn't look too user-friendly...
... but it was added to perf to made errors more user-friendly: http://lwn.net/Articles/460520/ "perf: make perf.data more self-descriptive (v5)" by Stephane Eranian , 22 Sep 2011:
+static int do_write_feat(int fd, struct perf_header *h, int type, ....
+ pr_debug("failed to write feature %d\n", type);
All features are listed here http://lxr.free-electrons.com/source/tools/perf/util/header.h#L13
15 HEADER_TRACING_DATA = 1,
16 HEADER_BUILD_ID,
So, it sounds like perf inject was not able to write information about build ids (error from function write_build_id() from util/header.c) if I'm not wrong. There are two cases which can lead to error: unsuccessful call to perf_session__read_build_ids() or failing in writing buildid table dsos__write_buildid_table (this is not our case because there is no "failed to write buildid table" error message; check write_build_id)
You may check, do you have all buildids needed for the session. Also it may be useful to clear your buildid cache (rm -rf ~/.debug), and check that you have up-to-date vmlinux with debugging info or kallsyms enabled in your kernel.
UPDATE: in comments Pavel says that his pref record had no any sched:sched_stat_sleep events written to perf.data:
sudo perf record -e sched:sched_stat_sleep -e sched:sched_switch -e sched:sched_process_exit -g -o ~/perf.data.raw ./a.out
As he explains in his answer, his default debian kernel have CONFIG_SCHEDSTATS option disabled with vendor's patch. The redhat did the same thing with the option in release kernels since 3.11, and this is explained in Redhat Bug 1013225 (Josh Boyer 2013-10-28, comment 4):
We switched to enabling that only on debug builds a while ago. It seems that was turned off entirely with the final 3.11.0 build and has remained off since. Internal testing shows the option has a non-trivial performance impact for context switches.
We can turn this on in debug kernels again, but I'm not sure it's worthwhile.
Josh Poimboeuf 2013-11-04 in comment 8 says that performance impact is detectable:
In my tests I did a lot of context switches under various CPU loads. I saw a ~5-10% drop in average context switch speed when CONFIG_SCHEDSTATS was enabled. ...The performance hit only seemed to happen on post-CFS kernels (>= 2.6.23). The previous O(1) scheduler didn't seem to have this issue.
Fedora disabled CONFIG_SCHEDSTAT in non-debug kernels at 12 July 2013 "[kernel] Disable LATENCYTOP/SCHEDSTATS in non-debug builds." by Dave Jones. First kernel with disabled option: 3.11.0-0.rc0.git6.4.
In order to use any perf software tracepoint event with name like sched:sched_stat_* (sched:sched_stat_wait, sched:sched_stat_sleep, sched:sched_stat_iowait) we must recompile kernel with CONFIG_SCHEDSTATS option enabled and replace default Debian, RedHat or Fedora kernels which have no this option.
Thank you, Pavel Davydov.
I finally found out how to make it work. The problem was that the default debian kernel is built without some config options, that perf needs to be able to monitor sleep times. It looks like CONFIG_SCHEDSTATS should be enabled to make kernel collect scheduler statistics. This is told to have some runtime overhead. Also I enabled CONFIG_SCHED_TRACER and some lock tracing options, but I'm not sure if they matter in my case. Anyway, no statistic data is collected in scheduler without CONFIG_SCHEDSTATS (see kernel/sched/ directory of kernel source).
Also, there is a very good article about perf written by Brendan Gregg, with a lot of usefull examples and some kernel options that are needed to make perf work properly.
Update: I checked the history of CONFIG_SCHEDSTATS in debian. I've checked out debian kernel patches and build scripts repo:
svn checkout svn://svn.debian.org/svn/kernel/dists/trunk/linux/debian
And then found CONFIG_SCHEDSTATS option there
$ grep -R CONFIG_SCHEDSTAT config/
config/config:# CONFIG_SCHEDSTATS is not set
This string was added to the repo in commit 10837, on 2008-03-14, with comment "debian/config: Do complete reorganization". Also, in this and this (thanks to osgx) bug reports it is told that CONFIG_LATENCYTOP, CONFIG_SCHEDSTATS options are not enabled because they can affect kernel perfomance. So, I think it just was never switched on in default debian kernels. I haven't found the discussion about scheduler stats option, though. If I do, I will write back here.
This works for me for "perf version 3.11.1" on an "openSUSE 13.1 (x86_64)" box.
Here is the output if you care:
# ========
# captured on: Sun Feb 16 09:49:38 2014
# hostname : *****************
# os release : 3.11.10-7-desktop
# perf version : 3.11.1
# arch : x86_64
# nrcpus online : 8
# nrcpus avail : 8
# cpudesc : Intel(R) Core(TM) i7-3840QM CPU # 2.80GHz
# cpuid : GenuineIntel,6,58,9
# total memory : 32945368 kB
# cmdline : /usr/bin/perf inject -v -s -i perf.data.raw -o perf.data
# event : name = sched:sched_stat_sleep, type = 2, config = 0x48, config1 = 0x0, config2 = 0x
# event : name = sched:sched_switch, type = 2, config = 0x51, config1 = 0x0, config2 = 0x0, e
# event : name = sched:sched_process_exit, type = 2, config = 0x4e, config1 = 0x0, config2 =
# HEADER_CPU_TOPOLOGY info available, use -I to display
# HEADER_NUMA_TOPOLOGY info available, use -I to display
# pmu mappings: cpu = 4, software = 1, tracepoint = 2, uncore_cbox_0 = 6, uncore_cbox_1 = 7,
# ========
#
# Samples: 0 of event 'sched:sched_stat_sleep'
# Event count (approx.): 0
#
# Overhead Period Command Shared Object Symbol
# ........ ............ ....... ............. ......
#
# Samples: 8 of event 'sched:sched_switch'
# Event count (approx.): 80099958776
#
# Overhead Period Command Shared Object Symbol
# ........ ............ ....... ................. .................
#
100.00% 80099958776 bla [kernel.kallsyms] [k] thread_return
|
--- thread_return
thread_return
do_nanosleep
hrtimer_nanosleep
SyS_nanosleep
system_call_fastpath
0x7fbc0dec6570
__GI___libc_nanosleep
(nil)
# Samples: 0 of event 'sched:sched_process_exit'
# Event count (approx.): 0
#
# Overhead Period Command Shared Object Symbol
# ........ ............ ....... ............. ......
#
#
# (For a higher level overview, try: perf report --sort comm,dso)
#
}
I am using Red Hat 5.5 and I am trying to run Sybase ASE 12.5.4.
Yesterday I was trying to use the command "service sybase start" and the console showed sybase repeatedly trying to initialize, but failing, the main database server.
UPDATE:
I initialized a database at /ims_systemdb/master using the following commands:
dataserver -d /ims_systemdb/master -z 2k -b 51204 -c $SYBASE/ims.cfg -e db_error.log
chmod a=rwx /ims_systemdb/master
ls -al /ims_systemdb/master
And it gives me a nice database at /ims_systemdb/master with a size of 104865792 bytes (2048x51240).
But when I run
service sybase start
The error log at /logs/sybase_error.log goes like this:
00:00000:00000:2013/04/26 16:11:45.18 kernel Using config area from primary master device.
00:00000:00000:2013/04/26 16:11:45.19 kernel Detected 1 physical CPU
00:00000:00000:2013/04/26 16:11:45.19 kernel os_create_region: can't allocate 11534336000 bytes
00:00000:00000:2013/04/26 16:11:45.19 kernel kbcreate: couldn't create kernel region.
00:00000:00000:2013/04/26 16:11:45.19 kernel kistartup: could not create shared memory
I read "os_create_region" is normal if you don't set shmmax in sysctl high enough, so I set it to 16000000000000, but I still get this error. And sometimes, when I'm playing around with the .cfg file, I get this error message instead:
00:00000:00000:2013/04/25 14:04:08.28 kernel Using config area from primary master device.
00:00000:00000:2013/04/25 14:04:08.29 kernel Detected 1 physical CPU
00:00000:00000:2013/04/25 14:04:08.85 server The size of each partitioned pool must have atleast 512K. With the '16' partitions we cannot configure this value f
Why do these two errors appear and what can I do about them?
UPDATE:
Currently, I'm seeing the 1st error message (os cannot allocate bytes). The contents of /etc/sysctl.conf are as follows:
kernel.shmmax = 4294967295
kernel.shmall = 1048576
kernel.shmmni = 4096
But the log statements earlier state that
os_create_region: can't allocate 11534336000 bytes
So why is the region it is trying to allocate so big, and where did that get set?
The Solution:
When you get a message like "os_create_region: can't allocate 11534336000 bytes", what it means is that Sybase's configuration file is asking the kernel to create a region that exceeds the shmmax variable in /etc/sysctl.conf
The main thing to do is to change ims.conf (or whatever configuration file you are using). Then, you change the max memory variable in the physical memory section.
[Physical Memory]
max memory = 64000
additional network memory = 10485760
shared memory starting address = DEFAULT
allocate max shared memory = 1
For your information, my /etc/sysctl.conf file ended with these three lines:
kernel.shmmax = 16000000000
kernel.shmall = 16000000000
kernel.shmmni = 8192
And once this is done, type "showserver" to reveal what processes are running.
For more information, consult the Sybase System Administrator's Guide, volume 2 as well as Michael Gardner's link to Red Hat memory management in the comments earlier.
Hope it's OK to jot this down, even if I cannot accept answer immediately (and hope it's OK for SO - as there is a C patch below):
It seems I screwed up the hard disk on my desktop PC ({DRDY err}). So I wanted to run a bootable media to run fsck, but the CD on this desktop is broken, so I can only use USB flash. I have a couple of USB thumbdrives with Ubuntu and Suse - these start booting on the desktop; but during boot, udev tries to detect hard drives, and since the hard disk is screwed, it just loops there, and the respective OS never finishes booting.
So I tried to download SystemRescueCd; I have this USB thumbdrive, on which I tried to install SystemRescueCD:
# lsusb with sudo, to retrieve all info
$ sudo lsusb -v -d 058f:6387 | grep -i 'id\|iManufacturer\|iProduct\|iSerial\|bInterface'
Bus 001 Device 043: ID 058f:6387 Alcor Micro Corp. Transcend JetFlash Flash Drive
idVendor 0x058f Alcor Micro Corp.
idProduct 0x6387 Transcend JetFlash Flash Drive
iManufacturer 1 takeMS
iProduct 2 Mem-drive Mini
iSerial 3 C5E7F0CC
bInterfaceNumber 0
bInterfaceClass 8 Mass Storage
bInterfaceSubClass 6 SCSI
bInterfaceProtocol 80 Bulk (Zip)
# search by serial:
$ find /dev/disk/by-id/ -name '*C5E7F0CC*'
/dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0:0-part1
/dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0:0
# list and get device node
$ ls -la /dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0:0
lrwxrwxrwx 1 root root 9 2013-03-25 20:37 /dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0:0 -> ../../sdc
$ ls -la /dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0\:0-part1
lrwxrwxrwx 1 root root 10 2013-03-25 20:37 /dev/disk/by-id/usb-takeMS_Mem-drive_Mini_C5E7F0CC-0:0-part1 -> ../../sdc1
# it is /dev/sdc - list disk info
$ sudo fdisk -l /dev/sdc
Disk /dev/sdc: 2108 MB, 2108686336 bytes
94 heads, 29 sectors/track, 1510 cylinders
Units = cylinders of 2726 * 512 = 1395712 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0003e405
Device Boot Start End Blocks Id System
/dev/sdc1 * 1 1511 2059263+ c W95 FAT32 (LBA)
I tried to use my Ubuntu 11.04 Natty netbook to image the thumbdrive - and I used both
the recommended usb_inst.sh installer; and
I tried to use unetbootin (via sudo apt-get install unetbootin);
in both of these cases, when I try to boot the USB thumbdrive on the desktop, the boot procedure fails with:
SYSLINUX 4.02 debian-20101016 CHS Copyright (C) 1993-2010 H. Peter Anvin et al
ERROR: No configuration file found
No DEFAULT or UI configuration directive found!
boot:
.... with prompt at boot. (In fact, unetbootin fails at "Verifying DMI Pool Data", before entering syslinux - probably because it is much older than the .iso I'm trying to image).
First I checked the md5 as mentioned in No Default or UI Configuration Found!
$ md5sum ./systemrescuecd-x86-3.5.0.iso
48552b9e905872bd5061eb112b73ea20 ./systemrescuecd-x86-3.5.0.iso
... but it seems OK, as per Sysresccd-versions.
Then I tried to reformat the drive to FAT16 (via sudo gparted /dev/sdc); and repeated both usb_inst.sh and unetbootin methods - again no dice. Funny enough, in all of these cases, if I try to run the flash USB thumbdrive in the QEMU emulator:
# sudo apt-get install qemu
sudo qemu -hda /dev/sdc
... it boots fine - showing the syslinux menu and so on; however, boot always fails on the desktop.
Here I should mention, that I could write down the following from the boot screen of the problematic desktop PC:
Award Modular BIOS v6.00PG
AMDRS740 BIOS
It has a boot menu accessed via F12, and in the boot menu, among other options, these are for USB:
...
USB-FDD
USB-ZIP
USB-CDROM
USB-HDD
...
Typically, I choose USB-HDD - but I've tried the others; either the procedure freezes before even entering syslinux - or the boot fails as described above.
There is advice to rename directories/files manually from isolinux to syslinux (Trying to boot from usb - Ask Ubuntu) - when I used usb_inst.sh, only syslinux/isolinux.bin would have to be renamed. There is also advice to copy syslinux.cfg to the root of the USB flash thumbdrive (Cannot boot Live USB, Linux - Super User). But still no improvements - syslinux is still complaining that it is missing the configuration file - which apparently is the syslinux.cfg.
Then I tried to look if it is possible to somehow "debug" syslinux; found log tracing/debugging/trouble shooting in syslinux - The Syslinux Project - reboot.pro:
> Do we have specific commands to trace or log syslinux?
Being open source, one is able to compile Syslinux and enable extra debugging output.
also [SOLVED] Stuck on boot: Syslinux Problem [Archive] - Ubuntu Forums: "_
Debugging syslinux is described at http://www.syslinux.org/wiki/index.php/Development/Debugging , but effective debugging (if I recall correctly) requires recompiling it to add the debug hooks._". However, Development/Debugging - Syslinux Wiki talks about something called bochs; and I suspect that is to debug syslinux itself - not necessarily to "debug" (or query) the environment it is in.
Anyways, at last, I could see no way out but to get syslinux from source; basically, this was needed so it builds:
sudo apt-get install nasm
sudo apt-get install uuid-dev
git clone git://git.kernel.org/pub/scm/boot/syslinux/syslinux.git syslinux-git
cd syslinux-git/
make OPTFLAGS+=-DDEBUG=1
Turns out, it isn't really clear how to enable such debugging, that will show what syslinux "sees" when plugged in a given computer; given that I do load into syslinux at boot, the problem is what does it see as a filesystem. I tried to enable the DEBUG environment variable as shown above (after adding override OPTFLAGS := to the Makefile) - but that, in itself, generated no new messages during boot failure. I have used the following command to "burn" the USB thumbdrive (after unmounting it from the Gnome applet):
sudo ./linux/syslinux --stupid --directory /syslinux --install /dev/sdc1
... and I've tried both with stupid and without (and both for the source-built version, and the one from the Ubuntu package repositories for Natty).
Grepping through the source, I realized there is something called rosh (Read-Only SHell) - however, that compiles as a rosh.c32 - and one is supposed to have it as a boot kernel option in syslinux.cfg - which, as noted, I cannot load. So rosh.c32 is unfortunately not much help for my problem.
However, given that rosh implements the ls command, I tried to copy relevant portions into the code of syslinux - and trigger a ls / listing of the root when syslinux scans for the configuration file. With those changes, recorded in syslinux-e40ba60-rosh-ls.patch; now I get the following when I boot:
SYSLINUX 4.06 CHS 5-ge40ba60* Copyright (C) 1993-2010 H. Peter Anvin et al
Listing: "/"
rosh_ls_arg_dir 0 files found
Listing: "/syslinux"
Listing: ""
CurrentDirName: "/syslinux/"
confignamebuf: /syslinux/extlinux.conf; realpath -1
confignamebuf: /syslinux/syslinux.cfg; realpath -1
confignamebuf: /boot/syslinux/extlinux.conf; realpath -1
confignamebuf: /boot/syslinux/syslinux.cfg; realpath -1
confignamebuf: /syslinux/extlinux.conf; realpath -1
confignamebuf: /syslinux/syslinux.cfg; realpath -1
confignamebuf: /extlinux.conf; realpath -1
confignamebuf: /syslinux.cfg; realpath -1
ERROR: No configuration file found
No DEFAULT or UI configuration directive found!
Interestingly; for the root /, the _ls function at least returns "0 files"; the others ("/syslinux", and the empty string "") already fail at the opendir call - and so the _ls function doesn't even get called!
I would have thought that my slapstick copying of the ls function would not work as intended; but running the thumbdrive in qemu on netbook, does in fact provide a full listing of files - and given that at least for /, the function gets called and returns on the desktop - I'd suspect that it does indeed work.
However, that still doesn't solve my problem - why does syslinux, after boot, see 0 files under the root /? What else could I do to debug this problem? I wouldn't mind patching some C code into syslinux - but I just don't know what I should be looking for, that would point me to correct preparation of the USB thumbdrive for booting on the desktop machine...
OK, I got it to boot...
First, I noted there are alternative mbr's in the built git source as per Mbr - Syslinux Wiki and HowTos - Syslinux Wiki, so I tried both mbr.bin and altmbr.bin - altmbr.bin like this:
$ printf '\1' | cat mbr/altmbr.bin - | sudo dd bs=440 count=1 conv=notrunc iflag=fullblock of=/dev/sdc
... but that didn't help much.
Finally, I noted that lsusb says "bInterfaceProtocol 80 Bulk (Zip)"; and I remembered reading something about ZIP drives somewhere, so tried to look it up - and finally found this:
syslinux/doc/usbkey.txt
The proper mode to boot a USB key drive in is "USB-HDD". That is the
ONLY mode in which the C/H/S geometry encoded on the disk itself
doesn't have to match what the BIOS thinks it is. Since geometry on
USB drives is completely arbitrary, and can vary from BIOS to BIOS,
this is the only mode which will work in general.
Some BIOSes have been reported (in particular, certain versions of the
Award BIOS) that cannot boot USB keys in "USB-HDD" mode. This is a
very serious BIOS bug, but it is unfortunately rather typical of the
kind of quality we're seeing out of major BIOS vendors these days. On
these BIOSes, you're generally stuck booting them in USB-ZIP mode.
THIS MEANS THE FILESYSTEM IMAGE ON THE DISK HAS TO HAVE A CORRECT
ZIPDRIVE-COMPATIBLE GEOMETRY.
....
The script "mkdiskimage" which is supplied with the syslinux
distribution can be used to initialize USB keys in a Zip-like fashion.
To do that, calculate the correct number of cylinders (31 in the
example above), and, if your USB key is /dev/sda (CHECK THE KERNEL
MESSAGES CAREFULLY - IF YOU ENTER THE WRONG DISK DRIVE IT CANNOT BE
RECOVERED), run:
mkdiskimage -4 /dev/sda 0 64 32
(The 0 means automatically determine the size of the device, and -4
means mimic a zipdisk by using partition 4.)
So, as recommended there, first I find the number of cylinders for my thumbdrive:
$ grep 512-byte /var/log/syslog | tail -n 1
Mar 25 22:33:34 mypc kernel: [50884.608687] sd 45:0:0:0: [sdc] 4118528 512-byte logical blocks: (2.10 GB/1.96 GiB)
# get number of cylinders:
$ wcalc '4118528/(64*32)'
= 2011
... then I continue with mkdiskimage. After that was done, I tried usb_inst.sh again - and realized that it will overwrite the partition 4 that mkdiskimage made, and make a partition 1 for itself instead. That means, one should copy those files fron usb_inst.sh in a backup elsewhere, then run mkdiskimage - then finally copy the backed up files back to thumbdrive again; here is a command line log:
# mkdiskimage is present in syslinux-git:
$ ./utils/mkdiskimage
Usage: ./utils/mkdiskimage [-doFMz4][-i id] file c h s (max: 1024 256 63)
....
# ... but also in Debian/Ubuntu packaging of syslinux
$ mkdiskimage -4 /dev/sdc 0 64 32
/usr/bin/mkdiskimage: /dev/sdc: don't know how to determine the size of this device
# use sudo - note this command takes a while to complete:
$ sudo mkdiskimage -4 /dev/sdc 0 64 32
Warning: more than 1024 cylinders (2011).
Not all BIOSes will be able to boot this device.
$ ls /dev/sdc*
/dev/sdc /dev/sdc4
$ sudo fdisk -l /dev/sdc
Disk /dev/sdc: 2108 MB, 2108686336 bytes
64 heads, 32 sectors/track, 2011 cylinders
Units = cylinders of 2048 * 512 = 1048576 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x866262cc
Device Boot Start End Blocks Id System
/dev/sdc4 * 1 2011 2059248 e W95 FAT16 (LBA)
# (make sure umounted / ejected)
# cd to usb_inst.sh directory; and
# run usb_inst.sh for /dev/sdc; note it will:
# write MBR and "Creating filesystem on /dev/sdc1..."
# and "installing boot loader on /dev/sdc1";
# regardless of the previous setup on partition 4:
sudo bash ./usb_inst.sh
# now no more partition 4:
$ ls /dev/sdc*
/dev/sdc /dev/sdc1
# ( mount /dev/sdc1 via disk applet )
$ rsync -a /media/SYSRESC /media/backup/
# ... duhh... - again now
# ( umount/eject via disk applet )
$ sudo mkdiskimage -4 /dev/sdc 0 64 32
Warning: more than 1024 cylinders (2011).
Not all BIOSes will be able to boot this device.
$ sudo ./linux/syslinux --install /dev/sdc4
# ( mount via disk applet )
$ rsync -a /media/backup/SYSRESC/ /media/31A8-40E9/
$ sudo qemu -hda /dev/sdc # works
# ( umount/eject via disk applet )
# boot on desktop - works! loads rescue64 and initram.igz...
The interesting thing is - even if there is the warning "Not all BIOSes will be able to boot this device."; somehow this problematic BIOS loads this thumbdrive without a problem (and the _ls function above lists fine). Also interesting - here I choose the USB-HDD boot option (not the USB-ZIP) and it still works ?!
So, as a partial answer - I guess the way to debug this, would be for syslinux to somehow write on the thumbdrive the CHS geometry it sees during the syslinux installation; and on boot, to query the BIOS (I guess) about which CHS geometry the BIOS sees - and then dump these two geometries to screen; if there is a mismatch, then it is likely one should run mkdiskimage (unfortunately, I wouldn't know how to code that into syslinux)
Going back to my original HDD problem - turns out also SystemRescueCD uses udev to probe for devices - and again the boot process cannot complete (even if I choose the boot option "all files to memory (docache)")... So I get messages like:
udevadm settle - timeout of 180 seconds reached, the event queue contains:
Activating dmraid (fake hardware raid) ...
Starting mdadm (linux software raid) ....
udevd[88] worker [91] unexpectedly returned with status 0x0100 ...
udevd[88] worker [91] failed while handling '/devices/pci0000:00/.../sdb/sdb1'
So, I either find a Live USB distro which does not probe for disks using udev - or I better take this HDD out, toss it into a HDD USB enclosure, and try fsck it on another computer (hopefully I'll be able to blacklist this drive from udev on a running system)
Edit Aug 24 2013: Back to this problem, I thought I'd jot down few extra notes:
Since I cannot yet afford the time to fix this PC and its faulty drive, I've used this USB thumbdrive to boot multiple operating systems: PartedMagic and SliTaz did also encounter errors on the hard disk - but apparently use different drivers to access it (so the DRDY ERR loop didn't start), and they could finish booting relatively fast. Then I tried building a custom Ubuntu 12.04 image (using ubuntu-builder) - and this one ended up in a DRDY ERR loop, which may take more than 5 minutes to complete, before the OS finishes booting. I have posted more about this in Bug #1216397 “
It should be possible to ignore (skip probing) a known bad disk partition at boot” : Bugs : “linux” package : Ubuntu.
There are a few interesting things in respect to syslinux, now that this USB thumbdrive is used to boot multiple operating systems. First of all, the thumbdrive is, still, first made bootable with syslinux --install while empty (which places a file ldlinux.sys in the partition's root) - which corresponds to the mkdiskimage step above; and only afterwards are files (like kernel images, and including /boot/syslinux/syslinux.cfg) copied to it.
Now, I'd first build the CD image ISO in ubuntu-builder, and test it using VirtualBox (as qemu on my machine is way too slow for that). Once the ISO image was shown to work as expected, then only the files under its casper directory are relevant for the USB thumbdrive thus prepared; and they can be referenced through a boot menu entry in syslinux.cfg. So, I'd edit the syslinux.cfg on the thumbdrive, and copy the casper image files (e.g. filesystem.squashfs) to the thumbdrive - and test it with qemu as above. Once this qemu step passed, I'd move the USB thumbdrive on the target PC with the broken drive - and interestingly, here I might get syslinux boot failures of multiple sorts (during different boot stages):
"No DEFAULT or UI configuration directive found!" (or sometimes a "Bad <something> ..." message), before the syslinux boot menu is shown - even if the debug, as above, would show that syslinux reads the filesystem on the thumbdrive correctly, and finds the /boot/syslinux/syslinux.cfg (which does have proper directives)!
"Invalid or corrupt kernel image", once the syslinux menu is shown, and the new kernel image (Ubuntu) chosen - even if the other images (found previously on the thumb) boot fine on the broken drive PC; and the new image boots fine from thumb in qemu on a different machine!
"/init: line 7: can't open /dev/sr0: no medium found", once the new (Ubuntu) image is chosen from syslinux menu, and it starts booting; this seems an Ubuntu specific message, appearing a few seconds after it starts booting. I still encounter it even if booting completes succesfully - when it's a problem, this message just loops repeatedly, not allowing the rest of the boot process to complete
It turns out, any of these can appear whenever I try to change and save the syslinux.cfg file on the thumbdrive; or when I make changes in the casper image files, and I rsync or copy them to the thumbdrive. Maybe the copying process (since it may change the sectors where the files are located on the thumb), "confuses" parts of the boot process - although, this shouldn't happen, since also the working procedure above starts from a blanked, syslinux'd thumbdrive, to which files are copied after; so I think this may point to failing sectors on the thumbdrive.
However, even in this state, the working procedure above seemed to be useful - because using it, I could recover the thumb back to a working state! In more detail, it goes like this:
Keep a copy of the thumbdrive files somewhere on a different disk (e.g. ~/thumbcopy) - but without the ldlinux.sys file.
Whenever you want to make a change (to syslinux.cfg or to bootable image files) - make sure this change is saved in ~/thumbcopy first
Now, say I've changed some files on the bootable thumbdrive directly, and I encounter one of the errors above. Then:
First, delete all files but the ldlinux.sys on the thumbdrive, e.g.: rm -rf $(ls -I"ldlinux.sys" /media/31A8-40E9/)
Then, rsync or copy (cp -arv ...) the files in ~/thumbcopy to the thumbdrive, e.g.: rsync -aP ~/thumbcopy/ /media/31A8-40E9/
Now, try boot the thumbdrive in the PC again - it usually boots fine!
I've encountered all three types of errors, because I'd often try to change/copy individual files directly in the thumbdrive: sometimes the change doesn't introduce a problem, so booting is fine - however, in many cases, it does introduce a problem. For some reason, using the above procedure I managed to recover the thumbdrive from either type of abovementioned problems - maybe it has to do with USB Flash delayed writes, maybe with USB Flash failing sectors, I cannot really tell... But in any case: deleting all files, and re-copying them in one go, does seem to be a worthwhile procedure to try in case of errors like that.
It's an ancient post, but in case others stumble upon this, I'll add an answer anyway.
If you're struggling to get syslinux to boot, ROSH (Read-only Shell) can be useful, as you mentioned. To start ROSH, you can simply type rosh at the boot: prompt (if you do have a working graphical menu, press escape to drop back to the boot: prompt.
Inside the shell, you have some basic commands to look around in your environment. For more documentation, see https://wiki.syslinux.org/wiki/index.php?title=Read-Only_SHell(rosh.c32)