It’s great that Linux nowadays supports all the power management features available on computers. But it’s odd that beside the buttons to trigger standby/hibernate – which are only available in a graphical interface – there are no simple console commands to put the computer to sleep or into hibernation.
I recently attempted to install a fresh CentOS on a pair of recycled (previously used in a different linux sistem) hard disks.
Of course I got the classical message that the disks already had RAID metadata on them: “Disk contains BIOS metadata, but is not part of any recognized BIOS RAID sets. Ignoring disk sda”
Sometimes it may be necessary to block access to some/all services offered by a server without shutting it down or disconnecting it from the network, at the same time displaying a message for users accessing websites on it.
You might have often encountered the “Argument list is too long” message when trying to rm -rf large amount of files. This happens often on large servers when trying to clean up the tmp folder. This is because the rm command has a pretty low count of supported parameters (filenames) while the tmp folder can become host to a terribly high number of files (millions in a period of years).
One of the tricks I’ve frequently had to use was to discover all the recently modified files within a hosting account (very useful information in case the account was recently hacked and changed files need to be restored).
By default, grub only instals itself on the first hard drive, no matter how many members there are in the RAID1 array.
One can easily install the grub bootloader on additional members of the RAID using the setup (hdX)…
Setting your hostname, IP address, netmask, gateway, DNS server via files
It is sometimes helpful to know what is going on behind the scenes or if you want to modify the network configuration via changing files.
For example, assume you want to modify the network configuration by modifying files with the following…
There are times when you inadvertently overwrite your Master Boot Record. The end result being that you are unable to boot into Linux. This is especially true when you are dual booting between windows and Linux OSes. Once when I was working in Windows XP, I accidentally clicked the hibernate button instead of shutdown. And windows somehow overwrote my MBR which housed the GRUB boot loader. At such times, it pays to have this cool tip at hand…
If you ever need to count the occurences of a character in all (or some) files, this next series of commands would come in handy: for f in `ls`; do cat $f; done | awk ‘{ for ( i=1; i<=length; i++ ) arr[substr($0, i, 1)]++ }END{ for ( i in …
The dd utility can be successfully used to create a backup of a filesystem (in lack of more specialised backup utilites). dd if=/dev/sdaX | gzip > /backup/sdaX.gz where sdaX is the partition you want to backup, and the /backup folder is located on a different disk/partition than the one you’re …
This function comes in handy when you want to make a compressed sector-by-sector backup of your Linux filesystem and you don’t want to include/waste space with the unused sector (which still have information on them) Running nice cat /dev/zero > zero.fill;sync;sleep 1;sync;rm -f zero.fill before the actual backup will make …
I updated my server’s operating system from Fedora Core 6 (on which VMware Server ran perfectly) to Fedora 8. Fedora 6 was running an older 2.6.25 (which VMware liked just fine), but Fedora 8 brought me the 2.6.26.6-49.fc8 kernel, which caused a lot of trouble.
After spending 5 hours looking everywhere for a solution (I even thought the newer v1.08 would work on this kernel – but it didn’t), I considered writing down what I did to finally get my virtual machines up and running:
