Backend.ai

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* NEW: Add support for user-specific dotfiles population in session containers (166)
* MAINTENANCE: Revamp the CI/CD pipelines (173)

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* FIX: Package version conflicts due to aiobotocore/botocore and python-dateutil, by removing no longer
used codes and aiobotocore dependency.

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* FIX: Support host-to-container PID mapping in older Linux kernels (lower than 4.1) which does not
provide NSPid field in /proc task status.
* FIX: Invalid ownership of several runtime-generated files in the container working directory such as
SSH keypair and basic dotfiles, which may prevent containers from working properly.
* MAINTENANCE: Update aiodocker to 0.17

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* IMPROVE: Skip containers and images with a unsupported (future) kernelspec version.
(lablup/backend.ai80)

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* NEW: Provide some minimal basic dotfiles in kernel containers by default (.bashrc and .vimrc) (160)
- Make the "ls" command always colorized using an alias.
* NEW: Add support for keypair-specific SSH private key setup (158)

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* ROLLBACK: SFTP throughput optimization. It has caused PyCharm's helper upload failures for its
remote interpreter and debugging support, while all other tested SFTP clients (Cyberduck, FileZilla)
have worked flawlessly.
- While we are investigating both the SSHJ library and dropbear part to find the root cause,
the optimization is hold back since working is better than fast.