These are the objectives Understand and use essential tools Access a shell prompt and issue commands with correct syntax Use input-output redirection (>, >>, |, 2>, etc.) Use grep and regular expressions to analyze text Access remote systems using SSH…
Category: Linux administration
Apache custom logging of user agent
CustomLog logs/user_agents “%{user-agent}i”
Misaligned partitions (and filesystems) cause increased i/o.
See eg 3Par doc: http://h20195.www2.hp.com/V2/GetPDF.aspx%2F4AA4-4519ENW.pdf “All RAID devices, including HP 3PAR arrays, incur the overhead of calculating new parity after a write. A single write that spans two RAID sets will require two parity calculations. Aligning Linux disk partitions to…
server time off, due to hardware clock out of sync
On reboot the server time can be out of sync, because hard clock is out of sync. This can be checked by running”hwclock; date” and comparing the results. In Red Hat 6, the ntpdate start-up script is is separate from…
How to get CORRECT memory usage for Linux
One of the most common mistakes made by Linux users, is to run free (Mem: line) or sar to get memory utilization. The memory used fields include the space used by the OS to cache files and directory info cace,…
Sar Grapher Updated
Sar Grapher has been updated. It now graphs Linux NFS Server performance data.
Sargrapher Now Graphs Total CPU time
Sar grapher now displays graphs of total CPU time used. This makes it more obvious of combination of user, system, I/O wait.
Lunix Core Files
To enable core file generation.. Configure core files to use the PID as a extension. Set “kernel.core_uses_pid = 1” in /etc/sysctl.conf and run “/sbin/sysctl -p /etc/sysctl.conf: or to add it temporarily run “/sbin/sysctl -w kernel.core_uses_pid=1” to change the running kernel. …
How to Reduce/Shrink a ext[234] File System
In order to shrink a file system, the file system must be unmounted. For example with a LVM Logical volume called testfilesystem in volume group testVG mount on /opt/testfilesystem ( /dev/testVG-testfilesystem or /dev/mapper/testVG-testfilesystem) that we want to make 162 GB in sise. First…
Listing Full RPM Package Name
To get a full list RPM name, like the RPM file name use the Query Format option (–qf or –queryformat). This is useful in comparing 2 systems, seeing 32 bit and 64 bit packages and finding the RPMs. This lists…