Creating differential backups with 7-Zip

This is so great I'm shamelessly copying command lines for my own archive (aka this blog) - but also providing link to original.

7zip commands to create a backup of files

First step is to create full backup which is fairly easy:

7za a c:\archive.7z  c:\folder_to_archive

Next is to create differential backup with name diff1.7z

7za u c:\archive.7z  c:\folder_to_archive  -ms=off -mx=9 -t7z -u- -up0q3r2x2y2z0w2!c:\diff1.7z

• Where command switches stand for:
• -mx=9 - best compression
• -t7z - 7z archive type

Wtf "-up0q3r2x2y2z0w2!c:\diff1.7z" is ?

Actions mask to determinite 7z behavior

p - File exists in archive, but is not matched with wildcard.

q - File exists in archive, but doesn't exist on disk.

r - File doesn't exist in archive, but exists on disk.

x - File in archive is newer than the file on disk.

y - File in archive is older than the file on disk.

z - File in archive is same as the file on disk

w - Can not be detected what file is newer (times are the same, sizes are different)

Number means action:

0 Ignore file (don't create item in new archive for this file)

1 Copy file (copy from old archive to new)

2 Compress (compress file from disk to new archive)

3 Create Anti-item (item that will delete file or directory during extracting). This feature is supported only in 7z format