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Unhide is a little handy forensic tool to find hidden processes and TCP/UDP ports by rootkits / LKMs or by another hidden technique. This tools works under both Linux / Unix, and MS-Windows operating systems. From the man page:

It detects hidden processes using three techniques:

  1. The proc technique consists of comparing /proc with the output of /bin/ps.
  2. The sys technique consists of comparing information gathered from /bin/ps with information gathered from system calls.
  3. The brute technique consists of bruteforcing the all process IDs. This technique is only available on Linux 2.6 kernels.

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Unix time (POSIX time) is a system for describing points in time, defined as the number of seconds elapsed since midnight Coordinated Universal Time (UTC) of January 1, 1970, not counting leap seconds.
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Linux Maximum Length Of A Host Name

While browsing Linux kernel source code I came across POSIX (Portable Operating System Interface) variable called _POSIX_HOST_NAME_MAX . It defines the maximum length of a host name (not including the terminating null) as returned from the gethostname function.

This variable sets the limit to the number of characters in a hostname under Linux.
$ grep '_POSIX_HOST_NAME_MAX' /usr/include/bits/posix1_lim.h

#define _POSIX_HOST_NAME_MAX    255

You can change limit and recompile the kernel to get bigger hostname.

See comment below for correct information.

Updated for accuracy.

Last time I wrote about how-to set or retrieve the CPU affinity of a running process given its PID or to launch a new COMMAND with a given CPU affinity.
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If you try to mount an ext3 Linux filesystem on a SAN from multiple nodes at the same time you will be in serious deep trouble.

SAN based storage allows multiple nodes to connect to same devices at the same time. Ext3/2 are not cluster aware file system. They can lead to a disaster such as kernel panic, server hang, corruption etc.

You need to use something which supports:

  1. Useful in clusters for moderate scale out and shared SAN volumes
  2. Symmetrical Parallel Cluster File System, Journaled
  3. POSIX access controls

Both GFS (RedHat Global File System) and Lustre (a scalable, secure, robust, highly available cluster file system) can be used with SAN based storage allows multiple nodes to connect to same devices at the same time.

Many newbie get confused as Linux offers a number of file systems. This paper (Linux File System Primer) discusses these file systems, why there are so many, and which ones are the best to use for which workloads and data.