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”
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).
As some of you may already know, vzdump is not included in the openvz repository for CentOS. If you need to use vzdump, you have to download its source and compile it yourself, unless you’re already using some VPS control panel that has it bundled.
Luckily, for all those who don’t use control panels and don’t want to compile vzdump themselves, there’s a quick workaround. SolusVM includes it in its repository, which apparently can be used even if you don’t have SolusVM installed on that particular server.
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).
This is my preferred list of modules for iptables on OpenVZ kernels (set in /etc/vz/vz.conf): ## IPv4 iptables kernel modules to be enabled in CTs by default IPTABLES=”ipt_REJECT ipt_tos ipt_TOS ipt_LOG ip_conntrack ipt_limit ipt_multiport iptable_filter iptable_mangle ipt_TCPMSS ipt_tcpmss ipt_ttl ipt_length ipt_state iptable_nat ip_nat_ftp ipt_owner ipt_REDIRECT” ## IPv4 iptables kernel modules …
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)…
Does the login to your newly installed CentOS 6 VPS using Virtualmin and ProFTPD fail?
Check your /var/log/secure for errors such as this :
proftpd: PAM unable to dlopen(/lib64/security/pam_stack.so): /lib64/security/pam_stack.so: cannot open shared object file: No such file or directory
proftpd: PAM adding faulty module: /lib64/security/pam_stack.so
If you are logging the above error your /etc/pam.d/proftpd was updated (incorrectly)…
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 …
