Disks and filesystems

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

Check a device for bad blocks

fdisk /dev/sdb # Deprecated

gdisk /dev/sdb

Manage disk (GPT) 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>

stat <file>

Show about all there is to know about <file>

getfacl <file>

Show the Access Control List (ACL) information for a file or directory

setfacl -m u:<username>:<perm> <file>

Add <perm> for <username> to <file>

setfacl -d -m u:<username>:<perm> <dir>

-d makes that all files in <dir> will get the <username>:<perm> added to the ACL

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

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

mount -a

Mount all filesystems in /etc/fstab with the auto option.

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

Enable mount by; mount <mountpoint>

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.

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

Same as above but do not mount 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 for more.

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