Disks and filesystems

badblocks -v- s /dev/sdb >badblocks.log

Check a device for bad blocks

fdisk /dev/sdb

Manage disk partitions

df -h

Show filesystem block usage in human friendly format

df -i

Show filesystem inode usage

df -P

Report file-system information in parseble format.

du -shx *

Report disk usage for all files and directories in the current directory. Do not count files on other filesystems (-x) and do not follow symbolic links (default)

ls -i <file>

Show inode of <file>

mount -t <fstype> -o <options> <devicefile> <mountpoint>

Mount a filesystem (fstype and options can be omitted often)

mount -o loop /path/to/my-iso-image.iso /mnt/iso

Mount an .iso file

fstab

Configuration file to store mounts. Example for NFS mounts:

<host>:<path> <mountpoint> nfs defaults 0 0

Now you can mount by; mount <mountpoint>

De line above means; mount the <path> exported by <host> on directory <mountpoint> using the NFS protocol with default setting (see below), do not automatically backup when dump is executed and do not fsck when mounted at boot time.

Defaults (specified by defaults) are for ext3 filesystems: rw,suid,dev,exec,auto,nouser,async (read/write, set userID, dev?, allow execution of executables, mount during boot and when mount -a is done, only root can mount this, do not wait for the host to have written to storage)

See the fstab wikipedia page.

Performance

The graphical utility Disks has a benchmark option.

dd if=/dev/zero of=./test.tmp bs=1G count=1 oflag=dsync;rm -f ./test.tmp

Check plain write speed

dd if=/dev/zero of=./test.tmp bs=512 count=1000 oflag=dsync;rm -f ./test.tmp

Latency test

On an empty disk you can do:

dd if=/dev/zero of=/dev/sdb bs=8k count=10k

Test disk write speed if no filesystem exists

Misc

/dev/null

The unix black hole. Write always succeeds with no effect at all.

/dev/zero

Provides an unlimited amount of null characters (ASCII 0). Can be used for cleaning disks or benchmarking (see #Performance)

Writing to /dev/zero is the same as writing to /dev/null