I do a lot of storage-related work, and often times need to grab WWPNs to zone hosts and to mask storage. To gather the WWPNs I would often times use the following script on my RHEL and CentOS servers:
#!/bin/sh
FC_PATH="/sys/class/fc_host"
for fc_adapter in `ls ${FC_PATH}`
do
echo "${FC_PATH}/${fc_adapter}:"
NAME=$(awk '{print $1}' ${FC_PATH}/${fc_adapter}/symbolic_name )
echo " $NAME `cat ${FC_PATH}/${fc_adapter}/port_name`"
done
This produced consolidated output similar to:
$ print_wwpns
/sys/class/fc_host/host5:
QLE2562 0x21000024ff45afc2
/sys/class/fc_host/host6:
QLE2562 0x21000024ff45afc3
While doing some research I came across sysfsutils, which contains the incredibly useful systool utility. This nifty little tool allows you to query sysfs values, and can be used to display all of the sysfs attributes for your FC adapters:
$ systool -c fc_host -v
Class = "fc_host"
Class Device = "host5"
Class Device path = "/sys/class/fc_host/host5"
fabric_name = "0x200a547fee9e5e01"
issue_lip =
node_name = "0x20000024ff45afc2"
port_id = "0x0a00c0"
port_name = "0x21000024ff45afc2"
port_state = "Online"
port_type = "NPort (fabric via point-to-point)"
speed = "8 Gbit"
supported_classes = "Class 3"
supported_speeds = "1 Gbit, 2 Gbit, 4 Gbit, 8 Gbit"
symbolic_name = "QLE2562 FW:v5.06.03 DVR:v8.03.07.09.05.08-k"
system_hostname = ""
tgtid_bind_type = "wwpn (World Wide Port Name)"
uevent =
Class Device = "host6"
Class Device path = "/sys/class/fc_host/host6"
fabric_name = "0x2014547feeba9381"
issue_lip =
node_name = "0x20000024ff45afc3"
port_id = "0x9700a0"
port_name = "0x21000024ff45afc3"
port_state = "Online"
port_type = "NPort (fabric via point-to-point)"
speed = "8 Gbit"
supported_classes = "Class 3"
supported_speeds = "1 Gbit, 2 Gbit, 4 Gbit, 8 Gbit"
symbolic_name = "QLE2562 FW:v5.06.03 DVR:v8.03.07.09.05.08-k"
system_hostname = ""
tgtid_bind_type = "wwpn (World Wide Port Name)"
uevent =
This output is extremely useful for storage administrators, and provides everything you need in a nice consolidated form. +1 for systool!
When you run ‘yum update’ on your Fedora system, the default yum configuration will keep the last 3 kernels. This allows you to fail back to a previous working kernel if you encounter an error or a bug. The number of kernels to keep is controlled by the installonly_limit option, which is thoroughly described in the yum.conf(8) manual page:
installonly_limit Number of packages listed in installonlypkgs to keep installed at the same time. Setting to 0 disables this feature. Default is ’0′. Note that this functionality used to be in the “installonlyn” plugin, where this option was altered via. tokeep. Note that as of version 3.2.24, yum will now look in the yumdb for a installonly attribute on installed packages. If that attribute is “keep”, then they will never be removed.
If you need to keep more than 3 kernels, you can increase the value of installonly_limit in /etc/yum.conf.
Most of the Linux distributions that utilize the yum package manager cache headers and packages by default. These files are cached in the directory identified by the cachedir option, which defaults to /var/cache/yum on all of the hosts I checked. On my Fedora 16 desktop this directory has grown to 167MB in size:
$ du -sh /var/cache/yum
167M /var/cache/yum
You can clean out the cached directory with the yum “clean” option:
$ yum clean all
If disk space is an issue on your systems, you can also set the “keepcache” option to 0. This will remove cached files after they are installed, as noted in yum.conf(8)the manual page:
keepcache Either `1' or `0'. Determines whether or not yum keeps
the cache of headers and packages after successful installation.
Default is '1' (keep files)
This is a useful option for hosts that have limited disk space. Nice!
I think humor plays a big role in life, especially the life of a SysAdmin. This weekend I was cleaning up some sudoers files and came across a reference to the “insult” option in the documentation. Here is what the manual says:
“insults If set, sudo will insult users when they enter an incorrect password. This flag is off by default.”
This of course peaked my curiosity, and the description in the online documentation got me wondering what kind of insults sudo would spit out. To test this feature out I compiled sudo with the complete set of insults:
$ ./configure –prefix=/usr/local –with-insults –with-all-insults
$ gmake
$ gmake install
To enable insults I added “Defaults insults” to my sudoers file. This resulted in me laughing myself silly:
$ sudo /bin/false
Password:
Take a stress pill and think things over.
Password:
This mission is too important for me to allow you to jeopardize it.
Password:
I feel much better now.
sudo: 3 incorrect password attempts
$ sudo /bin/false
Password:
Have you considered trying to match wits with a rutabaga?
Password:
You speak an infinite deal of nothing
Password:
You speak an infinite deal of nothing
sudo: 3 incorrect password attempts
Life without laughter is pretty much a useless life. You can quote me on that one! ;)
I previously described how to use strace to to summarize system call activity on Linux hosts. Solaris provides similar data with the truss “-c” option:
$ truss -c -p 26396
syscall seconds calls errors
read .000 3
write 7.671 25038
time .000 21
stat .000 15
lseek .460 24944
getpid .000 15
kill .162 7664
sigaction .004 237
writev .000 3
lwp_sigmask .897 49887
pollsys .476 7667
-------- ------ ----
sys totals: 9.674 115494 0
usr time: 2.250
elapsed: 180.940
The output contains the total elapsed time, a breakdown of user and system time, the number of errors that occurred, the number of times each system call was invoked and the total accrued time for each system call. This has numerous uses, and allows you to easily see how a process is intereacting with the kernel. Sweet!
Linux has a guadzillion debugging utilities available. One of my favorite tools for debugging problems is strace, which allows you to observe the system calls a process is making in realtime. Strace also has a “-c” option to summarize system call activity:
$ strace -c -p 28009
Process 28009 attached
Process 28009 detached
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
78.17 0.001278 2 643 select
14.80 0.000242 1 322 read
7.03 0.000115 0 322 write
------ ----------- ----------- --------- --------- ----------------
100.00 0.001635 1287 total
The output contains the percentage of time spent in each system call, the total time in seconds, the microseconds per call, the total number of calls, a count of the number of errors and the type of system call that was made. This output has numerous uses, and is a great way to observe how a process is interacting with the kernel. Good stuff!
