In normal git flow in case you have to checkout a file you would use:

git checkout -- your_file_name

In case you want to checkout multiple files you give other file names in front of checkout --. Sometimes there are bunch of modified files that you want to checkout all of them at once, so you need to go to the root of the project and:

git checkout -- .

It will checkout all files in your project.

You can also use:

git reset --hard

It will reset your working directory and replace all changes (including the index).

#git #checkout #reset #hard

Benchmark disk performance using hdparm & dd.

In order to get a meaningful result run the test a couple of times.


Direct read (without cache):

$ sudo hdparm -t /dev/sda2
 /dev/sda2:
  Timing buffered disk reads: 302 MB in  3.00 seconds = 100.58 MB/sec

And here's a cached read:

$ sudo hdparm -T /dev/sda2
 /dev/sda2:
  Timing cached reads:   4636 MB in  2.00 seconds = 2318.89 MB/sec

-t: Perform timings of device reads for benchmark and comparison
purposes. For meaningful results, this operation should be repeated
2-3 times on an otherwise inactive system (no other active processes)
with at least a couple of megabytes of free memory. This displays
the speed of reading through the buffer cache to the disk without
any prior caching of data. This measurement is an indication of how
fast the drive can sustain sequential data reads under Linux, without
any filesystem overhead. To ensure accurate measurements, the
buffer cache is flushed during the processing of -t using the
BLKFLSBUF ioctl.

-T: Perform timings of cache reads for benchmark and comparison purposes.
For meaningful results, this operation should be repeated 2-3
times on an otherwise inactive system (no other active processes)
with at least a couple of megabytes of free memory. This displays
the speed of reading directly from the Linux buffer cache without
disk access. This measurement is essentially an indication of the
throughput of the processor, cache, and memory of the system under
test.


You can use dd command to test your hard disk too:

$ time sh -c "dd if=/dev/zero of=ddfile bs=8k count=250000 && sync"; rm ddfile

rm ddfile removes the test file created by dd command of=ddfile. of param stands for output file.


These are some useful and simple disk benchmarking tools.

#linux #benchmark #hdd #dd #hard_disk #hdparm