Five ~/.ssh/config patterns I keep reusing

Every new laptop gets the same handful of blocks in ~/.ssh/config. Here they are, so that I stop rewriting them from memory.

1. Short aliases

Host web
    HostName 203.0.113.10
    User deploy
    Port 2201

ssh web instead of remembering an address, a user and a port. scp and rsync understand the alias too.

2. Jump hosts

Host db
    HostName 10.0.0.12
    ProxyJump web

The database box has no public address; ssh db goes through web without an agent being forwarded anywhere.

3. One key per host, and only that key

Host git-work
    HostName git.example.com
    IdentityFile ~/.ssh/work_ed25519
    IdentitiesOnly yes

IdentitiesOnly yes is the line that stops "Too many authentication failures" when the agent holds a dozen keys and offers all of them first.

4. Keepalives behind NAT

Host *
    ServerAliveInterval 30
    ServerAliveCountMax 4

Home routers forget idle connections. Thirty seconds is enough to keep a session open through most of them, and four missed replies end a dead one in two minutes instead of hanging forever.

5. Connection sharing

Host *
    ControlMaster auto
    ControlPath ~/.ssh/cm-%r@%h:%p
    ControlPersist 10m

The second ssh to the same host opens instantly over the first connection. After changing anything about a host, close the master with ssh -O exit web, or the old settings stay in use for ten more minutes.

Order matters: ssh takes the first value it sees for each option, so the specific Host blocks go above Host *.