FreeBSD got a builtin (part of ‘world’) command watch, so if you’re looking for the equivalent of the Linux watch command try ‘cmdwatch .
cli
Change default shell for several users
chsh is great when you need to change default login shell for a lot of users.
Something like:
for f in $(grep home /etc/passwd | grep -v ftp | cut -d':' -f1) ; do chsh -s /bin/sh $f ; done
You would of course have to refine the grep line to sort out accounts you don’t want to change default login shell for .
Had an ulimit problem
I’m optimizing some scripts that split our apache logs each night. I gotta admit Apache’s ‘split-logfile’ script written in perl is a LOT faster than doing it via f.example bash . But splitting up a log file with more than 2000 vhosts resluted in the script crashing. I had to up my ‘open files’ limit with :
# ulimit -n 4096 #
http://www.debian.org/doc/manuals/securing-debian-howto/ch4.en.html
http://httpd.apache.org/docs/2.0/programs/other.html
Testing read/write speed of disks
Upon testing the performance of a raid 6 array with 13 disks i wanted to check read/write performance, an easy way to do this fast on Linux (Debian) is simply using ‘time’ and ‘dd’:
bakis:/var/raid6volume# time dd if=/dev/zero of=./testingtransfer bs=16k count=16k 16384+0 records in 16384+0 records out 268435456 bytes (268 MB) copied, 1.48474 s, 181 MB/s real 0m1.513s user 0m0.008s sys 0m1.456s bakis:/var/raid6volume# time dd if=./testingtransfer of=/dev/null bs=16k 16384+0 records in 16384+0 records out 268435456 bytes (268 MB) copied, 0.156663 s, 1.7 GB/s real 0m0.159s user 0m0.004s sys 0m0.160s bakis:/var/raid6volume#
The ‘read’ test above isn’t real since the file has been cached . But a rsync is working in the background so I couldn’t umount /var/raid6volume for this example.
Initially I was doing this to test performance over nfs for the same array, one has to umount / mount the share between each test to make sure nothings in the cache.
Working with nfs, tuning wsize and rsize on the client side also gives a lot better performance (at least in my case), see the link bellow for more info.
I got these hints from debianhelp.co.uk
How much ram in my graphics card ?
Nice command to find how much ram my graphics card has. Use ‘lspci’ to get the pci id and throw it back to lspci like this:
joar@juno:~$ lspci | grep VGA 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 09) joar@juno:~$ lspci -v -s 00:02.0 00:02.0 VGA compatible controller: Intel Corporation Mobile 4 Series Chipset Integrated Graphics Controller (rev 09) Subsystem: Lenovo Device 3a02 Flags: bus master, fast devsel, latency 0, IRQ 30 Memory at f4000000 (64-bit, non-prefetchable) [size=4M] Memory at d0000000 (64-bit, prefetchable) [size=256M] I/O ports at 1800 [size=8] Capabilities: <access denied> Kernel driver in use: i915 Kernel modules: i915 joar@juno:~$