01-01-2020
I agree also,
I did lose files after crashes but in the early 90s on HP-UX 8, or Linux 0.99... can't remember after with JFS...
As Neo mentions, its not the OS crash the vulnerability but more the Human intervention on those files been modified e.g I saw Sun servers after a reboot where no one could connect, because someone modified the passwd file NOT using vi... and many more similar cases, so for peace of mind I always make a copy I modify and once done add .ori to the original so whatever I can compare... My remarks apply mostly to any Unix configuration files except sudoers need editing with vi ( as depending on the state of the machine is the only editor working...)
It is true that modern editors as Neo described have funky functionalities that are more than simple cosmetics and would be a pity not to use, but also as he adds: with caution..
What I wanted to mention was more: In a panic mode you tend to forget a lot of things like when a system crashes, you may well have a mail ( but who looks at his mbox?) from the system saying you were editing a file and the system saved the state of the file under the name XXXXXXX, you open them with vi -rdepending the content and how bad the crash you may find the system managed to leave the original in his precedent state ( so before editing or last save ) and have in XXXXXX the last state of current modifications of the file, it may not be complete but at least you haven't lost all, and most important it avoided your system some unwanted file corruption... this may be the reason of with JFS no one can remember losing anything these last 25 years...
But it's not a reason for not being careful when doing sysadmin tasks
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crash(8v) crash(8v)
Name
crash - what happens when the system crashes
Description
This section explains what happens when the system crashes and shows how to analyze crash dumps.
When the system crashes voluntarily it prints a message on the console in the form:
panic: explanation
The system takes a dump on a mass storage peripheral device or the network, and then invokes an automatic reboot procedure as described in
Unless there is some unexpected inconsistency in the state of the file systems due to hardware or software failure, the system then resumes
multi-user operations. If auto-reboot is disabled, the system halts at this point.
The system has a large number of internal consistency checks; if one of these fails, it prints a short message indicating which one failed.
The most common cause of system failures is hardware failure. In all cases there is the possibility that hardware or software error pro-
duced the message in some unexpected way. These messages are the ones you are likely to encounter:
IO err in push
hard IO err in swap
The system encountered an error when trying to write to the paging device or an error in reading critical information from a disk
drive. Fix your disk if it is broken or unreliable.
timeout table overflow
Due to the current data structure, running out of entries causes a crash. If this happens, make the timeout table bigger.
Exception Condition
An unexpected system error has occurred. The exception types are as follows:
---------------------------------------------------------------
Mnemonic Description
---------------------------------------------------------------
INT External interrupt
MOD TLB modification exception
TLBL TLB miss exception (load or instruction fetch)
TLBS TLB miss exception (store)
AdEL Address error exception (load or instruction fetch)
AdES Address error exception (store)
IBE Bus error exception (for an instruction fetch)
DBE Bus error exception (for a data load or store)
Sys Sys call exception
Bp Breakpoint exception
CpU Coprocessor unusable exception
Ovf Arithmetic overflow exception
---------------------------------------------------------------
KSP not valid
This indicates either a problem in the system or failing hardware.
init died
The system initialization process has exited. The only solution is the automatic reboot procedure described in Until this is done,
new users cannot log in.
When the system crashes, it attempts to write an image of memory into the back end of the primary swap area. After the system is rebooted,
the program runs and preserves a copy of this core image and the current system in a specified directory for later access. See for
details.
To analyze a dump, you should begin by running with the flag on the core dump.
See Also
dbx(1), reboot(8), savecore(8)
RISC crash(8v)