Hot answers tagged

76

Obviously, memtest86+ cannot test the memory region which currently contains the memtest86+ executable code (but if there are memory errors in that region, it is very likely that the test itself will crash). However, memtest86+ is able to relocate its own code to a different address at runtime, and by using this trick it is able to test all memory which it ...


29

Isn't this a situation where you should engineer around the circular dependencies? Set power-on delays in the server BIOS. You have multiple DNS servers, so that's a plus. DNS caching? Would this be as simple as using IP addresses or host files for your NFS or storage network? You didn't mention the particular virtualization technology, but it's possible to ...


25

First the lecture: Rule Number Zero: If you do not understand what something does, DO NOT TOUCH IT Deleting files "to save space" with no concept of what you are doing will anger the operating system gods, resulting problems similar to what you are now experiencing (Things break. Fixing them is often non-trivial). Now the sympathetic assistance: ...


22

You're looking at a lost cause. Save the data you need, and reinstall the operating system.


22

These days, 100 Megabytes or 200 Megabytes is the norm. You do not need to have a /boot partition. However, it's good to have for flexibility reasons (LVM, encryption, BIOS limitations). Edit: The recommended size has been increased to 300MB-500MB. Also see: http://superuser.com/questions/66015/installing-ubuntu-do-i-really-need-a-boot-parition


21

I tend to create a 1GB /boot. I leave a livecd image which has various repair tools in my /boot. I mostly do this for systems that at the remote sites I support. With the right configuration, and enough memory, grub2 can boot the image without extracting the contents. A couple times I have talked remote staff into rebooting the system to the livecd image ...


20

What is the recommended size for a linux /boot partition? The /boot parition contains the GRUB configuration, the kernel with their System.map, ... I think ~ 100MB is enough. And is it safe to not have a /boot partition? Yes. But a separate /boot partition has some advantages: as a rescue partition rootfs is on a LVM, RAID, is encrypted, or ...


19

In short: ls /etc/rc*.d This shows you what starts at which runlevel, and within each level the order is determined by the number after the letter (K is Kill, S is start). You can configure what starts at each runlevel with sysv-rc-conf, which is installable with apt. e.g. on my system apache2 is symlinked in rc5.d as "S20apache2". A link in the same ...


17

As per the recommendation of MadHatter here. I will post my answer here as an addendum to the answers here so that it may be used in conjunction with the answers suggested here. Taken from the following website ## Install yum utils ## yum install yum-utils ## Package-cleanup set count as how many old kernels you want left ## package-cleanup --oldkernels -...


17

Out of the box, you are guaranteed that iptables will start before the interface is brought up by the order of the startup scripts. Look at the "chkconfig" line in each startup script and you will see the runlevels it is "on" when active, the start order, and the stop order. You are not guaranteed that the interface will not be brought up if the iptables ...


16

It is possible to boot your Windows installed on your computer in a VM running on a Linux installed on the same computer. The only thing to remember: do not mount a partition on both OS. I've used this setup in qemu, kvm and VirtualBox. EDIT: The ideea is to use the entire physical disk and be careful not to mount the same partition twice (like booting the ...


15

I have done this only recently - works really well. I have an 8GB usb key with several ISO images on it. When I boot from the key, I get to choose which ISO to boot from. Pretty damn cool. This is all courtesy of GRUB. Instructions here: http://themudcrab.com/acronis_grub4dos.php In the example it is showing how to boot a single Acronis recovery ISO, but ...


15

I'd suggest just using the user-data option to ec2-run-instances. It lets you give a script of some sort to the VM which will be run on first boot. If you're using ubuntu or debian, you can use cloud-init, which puts some nice polish on the process. If using cloud-init, you can use the [runcmd] section of the config file to specify arbitrary commands to run ...


15

There's no option here. Since the advent of the Nehalem and newer CPU's, the POST time on HP systems has grown tremendously. I see that you're using this as a workstation. Is there any option to leave the system running and take advantage of some of the BIOS power management options?


15

You say in your comments that you're evaluating a netboot / network root environment. The first thing you must realize is there is no such thing as "vanilla" - you're not going to run CentOS 5.10 right out of the box with zero changes (if you think you are you're deluding yourself: NFS Root is already at least Strawberry, verging on Pistachio). If you want ...


14

Following command will remove ALL kernel versions, except for the one that you're currently running: sudo yum remove `rpm -q kernel | grep -v 'uname -r'` and for going forward, per ⁠7.4. Configuring Yum and Yum Repositories: ⁠installonly_limit=value …where value is an integer representing the maximum number of versions that can be installed ...


13

Is it this problem? You need to look at /etc/default/rcS and change UTC=yes to UTC=no. This makes Ubuntu read and write to the hardware clock in the same way as Windows, using local time instead of UTC.


13

All IBM uEFI Machines take ages to boot, as after the eon-taking uEFI initialization and module startup the legacy BIOS emulation kicks in and the PCI-E option ROMs get executed etc. etc. This is "normal" on all IBM uEFI machines - no matter if blade or standard rack server. You could disable legacy BIOS boot, the option ROMs, optimize the boot order and ...


13

You want update-rc.d mysql disable. You don't want remove, As noted in the update-rc.d manpage: A common system administration error is to delete the links with the thought that this will "disable" the service, i.e., that this will pre‐ vent the service from being started. However, if all links have been deleted then the next time the ...


12

Have a look at the update-rc.d man page. The third paragraph of the section named Installing Init Script Links reads … A common system administration error is to delete the links with the thought that this will "disable" the service, i.e., that this will prevent the service from being started. However, if all links have been deleted then the next ...


12

Create a disk image. The following command will create a 10G sparse image: # dd if=/dev/zero of=mydisk.img bs=1 count=0 seek=10G 0+0 records in 0+0 records out 0 bytes (0 B) copied, 1.6554e-05 s, 0.0 kB/s # ls -lh mydisk.img -rw-r--r--. 1 root root 10G Jun 17 15:27 mydisk.img Partition the image with fdisk: # fdisk mydisk.img Make sure you create ...


11

My understanding is that it loads only the minimum drivers/settings needed for a very basic windows boot. There are other options though such as starting with networking support (adding more drivers and settings to the boot), or the command prompt as as shell instead of Explorer. Safe mode helps you troubleshoot a windows installation with bad driver and/...


11

Why not just connect a USB CD\DVD drive and install from there?


11

If you look at the "chkconfig" line of /etc/init.d/network you'll see that the network has a start priority of "10". /etc/init.d/yourscript: #!/bin/bash # # yourscript short description # # chkconfig: 2345 9 20 # description: long description case "$1" in start) Do your thing !!! chkconfig yourscript off ;; stop|status|restart|reload|force-...


11

Depending on your UPS status, this could be one of the few use-cases where an ACPI hibernate may be a good idea. Generally restore-from-hibernate beats out a boot-from-scratch, especially in the case of low-RAM SSD-based systems. If you have the ability, the 'shutdown' step for your UPS software can be set to hibernate the DNS server.


11

Taken from the following website ## Install yum utils ## yum install yum-utils ## Package-cleanup set count as how many old kernels you want left ## package-cleanup --oldkernels --count=2 This will remove all older kernels and keep only the two most recent kernels on centos 6.4 which is probably what you want since recent kernels contain bug fixes and ...


10

You can use a Group Policy (or the local policy) to assign a startup script; you can configure it in the section Computer Configuration -> Windows Settings -> Scripts (Startup/Shutdown). You can also use Scheduled Tasks to configure a task to run at computer startup.


10

If you're already rebooting, just boot into the Live CD, chroot into the server's root filesystem, and run passwd. Problem solved.


9

NFS is notoriously touchy when it comes to mounts being unavailable at mount time or mounts disappearing randomly. Particularly with older Linux releases, there were some very real and serious issues with both cases. Recent releases have gotten a lot better, but aren't yet perfect. For this, however, I would strongly recommend looking into AutoFS and the ...


9

The boot messages come in two parts: those that come from the kernel (loading drivers, detecting partitions, etc) and those that come from the services starting up ([ OK ] Starting Apache...). The kernel messages are stored in /var/log/kern.log and can also be accessed from the kernel's own log buffer with the dmesg program. The userspace messages are not ...



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