Split and merge large files on Linux

Simple trick of how to split and merge back large files on Linux using split and cat commands. split and cat commands belong to the GNU core utilities which are expected to exist on every Linux operating system. Means, every Linux distro is already prepared for split/merge files and you only need to know how.

In my scenario, I wanted to copy virtual machine with 8GB disk image to the USB stick. USB stick has contained enough space but copying process stopped at 2GB with output message File too large. Here is report of file system disk space usage:

$ df -Th
Filesystem    Type    Size  Used Avail Use% Mounted on
/dev/sda1     ext2    7.9G  409M  7.1G   6% /
tmpfs        tmpfs    996M  552K  996M   1% /dev/shm
/dev/sdb5     ext4    204G   53G  141G  28% /home
/dev/sdb3     ext4    4.0G  140M  3.7G   4% /tmp
/dev/sda2     ext2     22G  5.8G   15G  29% /usr
/dev/sdb1     ext4     20G   13G  6.4G  66% /var
/dev/sdg1     vfat     16G  5.8G  9.5G  38% /media/CORSAIR

T” switch of df command prints file system type. As you can see, CORSAIR USB stick has VFAT (FAT32) file system. FAT32 has 4GB file-size limit but it’s signed (for +/- seeking within a file), so the limit is 1/2 the range, hence 2GB total. The only workaround was to split large file into pieces. With split command, 8GB file was sliced to four 2GB files (before start split process, be sure to have enough free space on disk):

# split [option] [input [prefix]]

$ split --bytes=2048m WinXP.img WinXP_img_

After several minutes, four files (2GB each) appeared in the same directory:


Now copying sliced parts to the USB stick had been without problems. After files were copied to the new Linux host, four pieces should be returned to the original form. cat command can concatenate files and here is how:

# cat [option] [file]...

$ cat WinXP_img_* > WinXP.img

Hope this simple scenario will help you to split/merge large files on Linux.

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