Sudden application crash in servers Post: 303009785

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Operating Systems HP-UX Sudden application crash in servers Post 303009785 by vbe on Wednesday 20th of December 2017 03:44:40 AM

12-20-2017

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The scanner is not in the server but somewhere on your network, internal I hope, or it may be an attack as mentionned... so in internal it seems there is something looking like a such device at the IP I pointed out - Check!
Years ago I had many HP-UX crashes once a month till I decided to write at the direction saying those "non-intrusive" devices were all but that and crashing HP servers or some mainframe devices, mostly the ones trusted and having/using NFS, the reason is mainly it opens so many connections id doesnt care for itself (MS.. OS?) but on a UNIX server the timeouts are regularly over 5 minutes so a opened port cannot be used till it is cleaned and so in such cases quickly you run out and then no one can connect, not even root and you are doomed... Once I proved where it came from the HP servers were listed out the scanning process... and now they changed system, but I have no more HP either... If you have NFS mounted on that server and the scan manages to make it unreadable then your system depending what is running will try to read desperatly and it s load will go beyond control till the system crashes...

vbe

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LEARN ABOUT OSF1

mountdtab

mountdtab(4)						     Kernel Interfaces Manual						      mountdtab(4)

NAME

       mountdtab - Table of local file systems mounted by remote NFS clients

SYNOPSIS

       /etc/mountdtab

DESCRIPTION

       The mountdtab file resides in the /etc directory and contains a list of all remote hosts that have mounted local file systems using the NFS
       protocols.  Whenever a client performs a remote mount, the server machine's mount daemon makes an entry in the server  machine's  mountdtab
       file.   The  umount  command  instructs the server's mount daemon to remove the entry.  The umount -b command broadcasts to all servers and
       informs them that they should remove all entries from mountdtab created by the sender of the broadcast message.	By placing  an	umount	-b
       command	in  a system startup file, mountdtab tables on NFS servers can be purged of entries made by a crashed client, who, upon rebooting,
       did not remount the same file systems that it had before the system crashed.  Tru64 UNIX systems automatically call  umount  -b	at  system
       startup

       The  format  for  entries  in  the  mountdtab  file is as follows: hostname:directory Rather than rewrite the mountdtab file on each umount
       request, the mount daemon comments out unmounted entries by placing a number sign (#) in the first character position  of  the  appropriate
       line.   The  mount daemon rewrites the entire file, without commented out entries, no more frequently than every 30 minutes.  The frequency
       depends on the occurrence of umount requests.

       The mountdtab table is used only to preserve information between crashes and is read only by the mountd daemon  when  it  starts  up.   The
       mountd daemon keeps an in-core table, which it uses to handle requests from programs like showmount and shutdown.

RESTRICTIONS

       Although the mountdtab table is close to the truth, it may contain erroneous information if NFS client machines fail to execute a umount -a
       command when they reboot.

RELATED INFORMATION

       mount(8), umount(8), mountd(8), showmount(8), shutdown(8) delim off

																      mountdtab(4)