Suggested I/O scheduler for a Video on Demand (VOD) server using Red Hat Enterprise Linux
On a VOD server, using the cfg scheduler can increase disk I/O latency when many connections arrive, leading to uneven video playback.
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394 notes on Linux, tools and troubleshooting
Decrease the time for rebuilding the RAID 1 array
To reduce RAID 1 rebuild time, use: # mdadm -C /dev/md0 -l1 -n2 /dev/sda1 /dev/sda2 --bitmap=internal. --bitmap (Write-intent bitmap) reduces synchronization time…
Re-shape or Grow a Raid 5 array.
Growing Linux software RAID is straightforward. This example adds /dev/sdd1 to a three-disk RAID 5 array at /dev/md0, then grows the array and filesystem.
How to enable xdmcp
The XDMCP configuration file has moved from /etc/X11/gdm/gdm.conf to /etc/gdm/custom.conf. To enable XDMCP, edit the section under xdmcp.
Other Virtual network interfaces go down when bring down virtual network interfaces
With multiple virtual network interfaces, bringing one interface down may also bring down others. This example uses eth0:0, eth0:1, eth0:2, and eth0:3.
Show line numbers in vi/vim editor.
Sometimes you need to find a specific line in a file, such as one identified by an error log. vi/vim can easily display or hide line numbers.
Increase the maximum file descriptors for Squid
If Squid logs WARNING! Your cache is running out of filedescriptors in cache.log, it was compiled with a maximum of 1024 file descriptors.
Reduce a non-root LVM.
This example reduces a 10 GB LVM volume to 8 GB, assuming it is mounted at /data, by shrinking the filesystem before reducing the logical volume.
View the commented lines of text in a config file
Use grep to display configuration lines that begin with particular characters. This helps inspect comments and review configuration settings.