systemd is like the service manager for your Centos and other modern Linux distributions (including Debian/Mint/Ubuntu) allows you to enable services, stop them, restart them, check their status and even reboot your system.
The key commands or arguments you will use with systemctl are the following:
list-units [PATTERN...] List loaded units
BootModuleConfig.sh echo host-ind nfcd ........
It's fairly simple to start or stop a check but I do wish mdadm's command had this built in. Sometimes it will do a check at the worst time causing the server to crawl to a halt.
Stop check on md126:
echo idle > /sys/block/md126/md/sync_action
Start check on md126:
echo check > /sys/block/md126/md/sync_action
This is especially helpful if you run your own servers. If you are presented with an error message or warning that the signature has changed or does not match the IP/domain you are connecting to you always want to verify manually.
So your e-mail/web client will show you an SHA-1 fingerprint like this:
"Could not verify this certificate because the issuer is unkown" or other reasons such as a mismatch in IP/domain.
It will also show you........
Solution To The Following:
yum -y install zlib-devel
yum -y install e2fsprogs*
*** Cannot find /usr/include/et/com_err.h. (yum install libcom_err-devel) ***
Installation didn't pass, halting install.
Once requirements are met, run the following to continue the install:
Common pre-install commands:
One of my test Centos 5 containers was on a partition that filled up and it threw all sorts of errors and stopped responding but now I can't boot it again anymore.
All the console shows is the Linux Penguin on the top left corner and the xm console says "usbcore: registered new driver hub" and has halted there.
Centos 5 Xen container stuck/frozen won't boot on "usbcore: registered new driver hub"
Another great way of troubleshooting is booting fro........
Many people aren't aware but recently Dual-Master Replication setups have become increasingly popular. That's because you get similar features and benefits of having a full-blown cluster (difficult to setup and maintain and requires I believe 3 servers just as controllers).
With a dual-master you just have a different off-set for the keys and you should be good, but of course there is the chance that at some point replication will halt because of an unexpected or unforseen error........
I've only used it on Centos, so I thought I'd make a quick Debian guide:
Install the DRBD Package
apt-get install drbd8-utils
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages were automatically installed and are no longer required:
Use 'apt-get autoremove' to remove them.
yum exits in the middle
The problem is this VPS seems to be an OpenVZ template from HyperVM. The only way to make it work was to disable i386 packages since this was an x64 kernel. That shouldn't be necessary but it was the only way to make yum stop quitting after the first package or two. I couldn't find any issue by checking the logs either.
echo y|yum install vim-minimal telnet expect jwhois net-tools slocate iptables elinks gawk
This happens on some systems due to a video issue with Intel Videocards, after you see the kernel load you may see almost immediately that you get a black screen.
The following kernel parameters usually solve it:
nomodeset i915.modeset=0 xforcevesa
some people just use "nomodeset" and others use "i915.modeset=0". I think nomodeset may also do the same for each video driver so it may imply i915.modeset=0 anyway but I am not sure.........
Different distributions such as Debian and Centos behave differently when trying to shutdown your system.
shutdown -H now on Debian does not do what you'd expect. The system won't power down, it will halt and do everything but power down.
shutdown -PH now will do the job though (actually power the system off). This is important to test especially if you are not near the system. If you just use -P it forcefully shuts off which is not........
md: Autodetecting RAID arrays.
md: autorun ...
md: considering sdb1 ...
md: adding sdb1 ...
md: adding sda1 ...
md: created md0
md: running: <sdb1><sda1>
md: kicking non-fresh sda1 from array!
raid1: raid set md0 active with 1 out of 2 mirrors
The md0 raid kicked sda1 ou........
This is obviously a bug in the r8169 kernel module and it seems to affect a lot of people. I upgraded to the latest kernel and hope this won't happen anymore, as it is a very serious error. This is especially serious for those who are running servers with this chipset, who can afford for the NIC to randomly go off-line for no apparent reason?
[655548.189113] type=1505 audit(1277067560.902:5): operation="profile_load" name="/usr/bin/freshclam&q........
I've never understood how to enable and disable services for different run levels in Debian based distros, it's just weird, annoying and doesn't make sense. I much prefer chkconfig from RHEL.
Just install the package called 'rcconf' and be done with it. rcconf makes things easy for you.
apt-get install rcconf
Reading package lists... Done
Building dependency tree
Reading state information... Done........
Out of memory: kill process 7559 (rsync) score 635 or a child
Killed process 7559 (rsync)
I was surprised to see this in my dmesg when my rsync backup suddenly stalled/stopped.
This system has 3 gigs of RAM and lots of free memory so I don't understand what is happening.
rsync invoked oom-killer: gfp_mask=0x200d2, order=0, oomkilladj=0
Pid: 7600, comm: rsync Not tainted 126.96.36.199 #83