RSYNC is a versatile file copying tool used predominantly in Unix and Linux systems. It’s popular for its efficiency in transferring and syncing files across systems, only copying the portions that have changed which saves significantly on bandwidth and time. However, a common error you might encounter during usage is the “RSYNC error: not enough memory”.
This error typically manifests when there’s a shortage of RAM to carry out the task. RSYNC uses considerable memory when dealing with a large number of files. When the allocated memory is insufficient, the system initiates a process known as swapping, where it temporarily moves some of the least used pages of memory to the disk. However, swapping is a considerably slower process, and if there’s still not enough RAM, you’ll get the RSYNC error.
To resolve this error, there are a few methods:
1. Increase Swap Space: You can create a swap partition or increase your existing swap space. Using swap space as an extension of RAM, the system writes less-used memory pages onto your hard drive. But keep in mind that using swap space can be slower since reading and writing to a hard drive is slower than RAM.
1. Methods to reduce memory usage by RSYNC:
a. Using ‘–no-inc-recursive’: This flag prevents RSYNC from increasing recursion, thereby saving memory but incrementally slowing down the process. b. Using ‘–delete-during’ or ‘–delete-after’: RSYNC, by default, uses ‘–delete-before’, which keeps both the file list and the deletion list in the memory. Switching to ‘–delete-during’ or ‘–delete-after’ can help in reducing memory usage. c. Usage of ‘–filter’ instead of ‘–exclude’: ‘–exclude’ constructs a list of files to ignore, which uses more memory. Switching to ‘–filter’ can save on memory.1. Upgrade Your Memory: If memory usage is consistently high, you might need to consider upgrading your system’s RAM. RSYNC uses 100 bytes of memory for every file it processes, so handling a large number of files would consume a significant amount of memory.
Knowledge of how RSYNC runs and manages memory can be inferred from the man pages (`man rsync`) and the official RSYNC webpage [3]. The specifics of the error can be found in various Linux user forums, such as StackOverflow, Unix & Linux Stack Exchange, and more. These communities often provide credible and test-verified approaches to solve such common errors. For memory upgrade instructions and hardware-related queries, your system manufacturer’s official guides and manuals serve as the best reference.
All in all, you must remember that while the above solutions might come handy in resolving the memory error in RSYNC, each has its own trade-off, and must be approached based on your system’s specific requirements.
Sources:
1. https://linux.die.net/man/1/rsync
2. https://unix.stackexchange.com/questions/88644/how-to-understand-which-processes-consuming-more-memory
3. https://rsync.samba.org/faq.html
4. https://linuxize.com/post/how-to-add-swap-space-on-ubuntu-18-04/
5. https://askubuntu.com/questions/207663/rsync-complain-about-not-enough-memory
