mount /dev/sda3 /xxx -t ext4
dziala
mout -aproc /proc proc defaults 0 0
/dev/sda1 / ext4 relatime,errors=remount-ro 0 1
/dev/sda2 none swap sw 0 0
/dev/sda3 /xxx ext4 0 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec,utf8 0 0
mount: wrong fs type, bad option, bad superblock on /dev/sda3,
missing codepage or helper program, or other error
In some cases useful info is found in syslog - try
dmesg | tail or so
[76641.423402] EXT4-fs: mballoc: 1796211 blocks 5047 reqs (4147 success)
[76641.423405] EXT4-fs: mballoc: 951 extents scanned, 4881 goal hits, 166 2^N hits, 0 breaks, 0 lost
[76641.423408] EXT4-fs: mballoc: 113 generated and it took 351495
[76641.423409] EXT4-fs: mballoc: 1206043 preallocated, 26199 discarded
[76643.077743] EXT4-fs: Unrecognized mount option "0" or missing value