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…
Tag: linux
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. …
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…
Increasing Linux Ring Buffer Size
This doesn’t work on all drivers, but on the bnx2x and other it does. In particular, if you are seeing packet drops this can help. Use ethtool –g <interface> to see the buffer settings. # ethtool -g eth0 Ring…
Working with files names that have spaces and special characters
Sometimes you need to work with multiple files that have spaces in their names. To do this you can backslash the special characters (\) or put quotes around their names..If you use filename completion, it should backslash the characters for…
Listing SSL cipher/protocols on remote host
To get a list of ciphers use nmap: nmap –script ssl-cert,ssl-enum-ciphers -p 443 www.example.com Starting Nmap 5.51 ( http://nmap.org ) at 2014-05-12 12:11 CDT Nmap scan report for www.example.com (10.10.10.10) Host is up (0.021s latency).%MCEPASTEBIN% PORT STATE SERVICE 443/tcp open…
Adding swap file to Linux
If there are no free partitions on a disk, you can create a swap file. Here is how you add a 12GB file. # Check what you have for swap. We have one 4GB swap partition. server# swapon -s Filename …