Posted on in system_administration
This guide is based on practical notes taken while tuning DRBD (Distributed Replicated Block Device) on a Linux system. DRBD is a software-based, shared-nothing, replicated storage solution for mirroring the content of block devices (hard disks, partitions, logical volumes, etc.) between servers. Proper tuning of DRBD can significantly improve performance …
Posted on in system_administration
DRBD, which stands for Distributed Replicated Block Device, is a software-based, shared-nothing, replicated storage solution for mirroring the content of block devices (such as hard disks, partitions, logical volumes, etc.) between servers. It is often used to build high-availability (HA) clusters and is integrated into the Linux kernel, making it …
Posted on in system_administration
Note: Although this is a continuation of the TCP Performance Tuning article series, it's also valuable as a standalone reference.
This list includes a mix of both well-established and newer algorithms, reflecting the ongoing advancements in TCP congestion control research and deployment. Algorithms like CUBIC and BBR are particularly notable …
Posted on in System Administration
I use Pingdom's free service to monitor slaptijack.com. Apparently,
late Friday night, oom-killer decided that the server needed more memory and
took out the MySQL server. To make matters worse, I missed the alarm from Pingdom,
and slaptijack.com was down for pretty much all of Saturday. The fact …
Posted on in System Administration
If you have a directory that you want to keep clean, tmpreaper is a great way
to remove files based on how old they are. The other day, I had a directory that
looked like this:
x@x:~/dump$ ls -l
-rw-r--r-- 1 x x 212268169 Mar 15 01:02 …Posted on in System Administration
I stumbled across this problem when a daily cronjob on one of our Debian servers complained about this. A lot. If you run across this on one of your systems, there is a quick fix.
In our case, it turned out that /usr/bin/mandb could not read /etc/passwd …
Posted on in System Administration
Posted on in System Administration
In the past, I've written about the usefulness of
using iptables to limit incoming SSH connections.
Although it isn't a replacement for a good password policy, it at least limits
the ability of outsiders to perform a brute-force password attack on your system.
Now that I've started using Ubuntu more …
Posted on in System Administration
Posted on in System Administration
Although this process is well documented on the Ubuntu community site, I decided to take notes of the exact steps that I took so that I wouldn't have to fumble through that long document next time. I'm installing the tools in a clean install of Ubuntu 10.04.2 LTS …
Posted on in Software
Red Hat finally announced the release of Red Hat Enterprise Linux (RHEL) 6 yesterday. RHEL 5 was released in early 2007, making the wait for RHEL 6 the longest since Red Hat rebranded their Linux-based operating system with the RHEL moniker in 2003.
RHEL 6 boasts tons of new features …
Posted on in System Administration
If you're using a non-standard MySQL data directory on your Red Hat Enterprise Linux (RHEL) server, you may have seen an error like /usr/libexec/mysqld: Can't change dir to '/mysql_data/' (Errcode: 13). The key to fixing this problem is to ensure the new MySQL data directory has the proper …
Posted on in System Administration
As every system administrator is aware, keeping precise time on your servers can be critical. For example, if you use QueueMetrics for your Asterisk-based call center and the QM and MySQL servers are running with different times, users will notice confusing behavior as calls seem to arrive in the future …
Posted on in System Administration
Configuring your syslog server to accept logging output from your Cisco routers and switches requires a few basic steps. We'll assume that you are using a new server and haven't made any previous changes to the syslog configuration. I use <acronym title="Red Hat Enterprise Linux">RHEL</acronym> 5 most …
Posted on in System Administration
If you've ever seen this, you've felt my pain:
# mount -vv -t nfs4 slap:/export/a/b/c /mnt
mount: pinging: prog 100003 vers 4 prot tcp port 2049
mount.nfs4: slap:/export/a/b/c failed, reason given by server: No such file or directory
My original thought was …
