I have bought new linode (1GB).   On this page :  Linode says:     Below are the suggested values for a 1GB Linode:   File:/etc/apache2/mods-available/mpm_prefork.conf  &lt;IfModule mpm_prefork_module&gt;         StartServers            2         MinSpareServers         6         MaxSpareServers         12         MaxRequestWorkers       39         MaxConnectionsPerChild  3000 &lt;/IfModule&gt;   But I'll plan to upgrade 2GB OR 4GB machine. What should be above values for 2GB or 4GB machine and WHY?  OS: Ubuntu 16.04 LTS
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This is a  about  Related:      I have a question regarding capacity planning. Can the Server Fault community please help with the following:   What kind of server do I need to handle some number of users? How many users can a server with some specifications handle? Will some server configuration be fast enough for my use case? I'm building a social networking site: what kind of hardware do I need? How much bandwidth do I need for some project? How much bandwidth will some number of users use in some application?
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I have a production server running with the following flag: -XX:+HeapDumpOnOutOfMemoryError  Last night it generated a java-38942.hprof file when our server encountered a heap error. It turns out that the developers of the system knew of the flag but no way to get any useful information from it.  Any ideas?
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I was reading through the hardware requirements of  and it says:     1 GB of RAM (1.5 GB if running on a virtual machine)   Why does running on a VM require more resources?
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I'm attempting to mount a partition from a NAS and the block size is 65536 bytes, this is above my distribution's precompiled kernel memory paging size of 4KiB, so I cannot mount it normally.  Which kernel compilation parameters would I need to change to get a memory paging size large enough?  Would it be possible under the x86-64 architecture?  EDIT: There doesn't seem to be an option for it in make xconfig unless I'm just missing it.  From page_types.h under arch\x86\include\asm  /* PAGE_SHIFT determines the page size */ #define PAGE_SHIFT  12 #define PAGE_SIZE   (_AC(1,UL) &lt;&lt; PAGE_SHIFT) #define PAGE_MASK   (~(PAGE_SIZE-1))`   It doesn't look to be configurable.  I could change this number directly to 16 and it would probably make pretty explosions and destroy Tokyo.  I shall probably try it later this evening.
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I created a file   touch /datastore/virtual/pseudoblock   created a loop device with it  sudo losetup /dev/loop0 /datastore/virtual/pseudoblock   (although I got a warning about its size)  and then initialized it with random data  dd if=/dev/urandom of=/dev/loop0 bs=1M count=100   My questions are  a) why is it not displayed yet in my block devices' list?  NAME                     MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT sdb                        8:16   0 489.1G  0 disk   ├─sdb2                     8:18   0   488M  0 part  /boot ├─sdb3                     8:19   0 488.1G  0 part   │ └─sdb3_crypt           253:0    0 488.1G  0 crypt  │   ├─ubuntu--vg-root    253:1    0 472.2G  0 lvm   / │   └─ubuntu--vg-swap_1  253:2    0  15.9G  0 lvm   [SWAP] └─sdb1                     8:17   0   512M  0 part  /boot/efi sda                        8:0    0 931.5G  0 disk   └─sda1                     8:1    0 931.5G  0 part     └─sda1_crypt           253:3    0 931.5G  0 crypt      └─store--vg-store1tb 253:4    0 931.5G  0 lvm   /datastore   b) how can I permanently mount it via /etc/fstab since I cannot get its UUID?  $ blkid /dev/mapper/sdb3_crypt: UUID="fSHjbj-51K2-QfhI-G0Wb-o3lN-4pE1-BB4wCP" TYPE="LVM2_member" /dev/mapper/ubuntu--vg-root: UUID="9e452886-4d8g-fj54-854c-80bc171826e8" TYPE="ext4"   working on   $ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description:    Ubuntu 16.04.5 LTS Release:    16.04 Codename:   xenial   with  $ uname -a Linux pkara-pc01 4.15.0-42-generic #45~16.04.1-Ubuntu SMP Mon Nov 19 13:02:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
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I was told I can add the -XX:+HeapDumpOnOutOfMemoryError parameter to my JVM start up options to my JBoss start up script to get a heap dump when we get an out of memory error in our application.  I was wondering where this data gets dumped?  Is it just to the console, or to some log file?  If it's just to the console, what if I'm not logged into the Unix server through the console?
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I am planning to rent a VPS service with following basic specification:   512mb of RAM 1 CPU 20gb HDD (4gb of it is swap) Ubuntu 10.10 server   I am able to choose between a 32 bit or 64 bit install of Ubuntu server as the operating system.   My question is would it be better to chose a 32 bit operating system since I will have only 512mb of RAM, rather than using a 64 bit operating system and dealing with the additional overheads?  edit:  I have installed Ubuntu server 10.10 32 bit and 64 bit on VirtualBox. After a minimalistic installation with only ssh server, the 32 bit installation consumes 63mb of RAM when first boot up and 64 bit consumes 85mb of RAM.  After installing and running  daemon, 32 bit consumes 99mb of RAM when first boot up and 64 bit consumes 128mb.
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I'm currently using a Joyent Accelerator to host my webapps, and it's working fine, however I need to reduce costs so I'm downgrading my current plan and that imposes some new memory limits (256M rss, 512M swap). I wasn't too far over them yesterday, but after restarting Apache several times today, I'm now 411M rss, 721M swap (prstat -Z -s cpu).  Searching in Server Fault only gives me lots of ways and specific tools to monitor the server, but no advice on how to reduce/optimize it's memory usage. I've also seen , but I don't think it's good for this particular (or may I say generic?) situation.  The server is running Solaris on a shared CPU, and I'm using a Apache + MySQL + PHP stack.  I'm interested in knowing the steps one can take to troubleshot this and solve the issues. However, I'm also running out of time to lower my memory foot print and downgrade the plan before the current ends, so anything that can make magic and save the day is welcome as well :)
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My root filesystem is running out of inodes.  If this were an issue of disk space, I'd use du -s to get a top-level overview of where the space is going, then head down the directory tree to find particular offenders.  Is there an equivalent option for inodes?   will point out individual directories with high usage, but in my case, that's no good: the Linux source directory, for example, gets scattered across 3000+ directories with low inode counts, rather than showing up as /usr/src/linux-4.0.5 52183.
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I'm looking for a near-zero-configuration linux distro that is designed specifically for serving static web sites and nothing else on a low-RAM machine (I'm planning on 128MB, but the option of less would be nice).  Any ideas of a linux distro specifically tuned for serving static sites in a small footprint?
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We're about to install a memory intensive application and will purchase a server for it.  The server will have at least 4 CPUs, with multiple cores. While the application is memory intensive, the consultants we're speaking with said that 32GB should be sufficient.  They also said that if I add more memory than that, the server will slow down because of the "extra wiring" to connect all of the memory.  I'm not planning on putting VMs on the hardware so I don't need extra memory to partition for virtual machines.  However I am concerned that 32GB may not be enough.  Does the consultant's assertion that more memory than I need will slow the machine down correct?
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Every time update manager prompts an update I get a message saying that there is not enough space available, however  the partition with Ubuntu installed  has over 10 GB of free space available.  I'm lost as to what needs to be done.  df -h returns:  Filesystem            Size  Used Avail Use%   Mounted on /dev/loop0            5.6G  5.1G  237M  96% / udev                  2.0G  4.0K  2.0G   1% /dev tmpfs                 786M  792K  786M   1% /run none                  5.0M     0  5.0M   0% /run/lock none                  2.0G  332K  2.0G   1% /run/shm /dev/sda6              20G  6.7G   13G  34% /host /dev/sda5             175G  120G   56G  69% /media/DATA   It would be great if someone could help me out on how to solve this problem. I'm a newbie to Ubuntu.
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I use PBKDF2-SHA512 with an iteration count of 128,000 to hash my passwords. I use a CSPRNG to generate a salt per password. However, I am unsure about the ideal size of the salt. I have read a lot of things about the salt size, but I have been unable to find a definitive answer. All of them agree that there is a minimum salt size, but I have found nothing about a maximum salt size.  So, here's my question: is there a point where the salt size doesn't matter anymore in terms of security and where it might even decrease it? If there is no maximum salt size, does it mean that the size we choose is actually a sweet spot among performance/space for salt storage/protection against precomputed tables?
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What I understand about 32-bit OS is, the address is expressed in 32 bits, so at most the OS could use 232 = 4G memory space -- I assume the unit is bytes, so 4GB.  Does this mean if any machine with a 32-bit OS (be it Windows or Unix) has more than 4GB total of RAM + page file on hard disk, for example 8GB RAM and 20GB page file, its memory will never be "used up"?  By "used up" I mean that increasing RAM or page file won't help the performance; of course, it's always possible an application will keep requesting memory from the OS but failing.  Similarly, if this 32-bit OS machine has 2GB RAM and 2GB page file, increasing the page file size won't help the performance. Is this true?
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Is there a (technical or practical) limit to how large you can configure the maximum number of open files in Linux?  Are there some adverse effects if you configure it to a very large number (say 1-100M)?  I'm thinking server usage here, not embedded systems.  Programs using huge amounts of open files can of course eat memory and be slow, but I'm interested in adverse effects if the limit is configured much larger than necessary (e.g. memory consumed by just the configuration).
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describes the RAM specifications for many of the MacBook laptops. In the section for my laptop (13" Pro Late 2011), it says:     Additional Notes: For best performance, fill both memory slots, installing an equal memory module in each slot.   This isn't the first time I've heard of this phenomenon, and it's definitely not specific to Apple.   Why is this the case? Other than the obvious decrease in available memory, why would it be worse to run with 6GB (1x4GB + 1x2GB) than with 8GB (2x4GB)?
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I read on  that Ubuntu will no longer use the familiar file size units we all know by now (kB, MB, GB, TB) and switch to a different IEC standard (KiB, MiB, GiB, TiB). If this is true, I would like to know what's the reasoning behind this change, and the impact (if any) this change has, especially with multiplatform applications or applications run with Wine.