$ rustup update
info: syncing channel updates for 'stable-x86_64-unknown-linux-gnu'
error: could not download file from 'https://static.rust-lang.org/dist/channel-rust-stable.toml.sha256' to '/home/alex/.rustup/tmp/n6b91922kkyrvmlh_file'
info: syncing channel updates for 'nightly-x86_64-unknown-linux-gnu'
error: could not download file from 'https://static.rust-lang.org/dist/channel-rust-nightly.toml.sha256' to '/home/alex/.rustup/tmp/mb54blu9ah_jdzen_file'

   stable-x86_64-unknown-linux-gnu update failed - rustc 1.22.1 (05e2e1c41 2017-11-22)
  nightly-x86_64-unknown-linux-gnu update failed - rustc 1.24.0-nightly (687d3d15b 2018-01-02)