How to Configure Putty to work in RDM

— ny_wk

When you embed multiple PuTTY sessions inside Remote Desktop Manager (RDM) and switch between tabs, PuTTY can collapse its terminal to a 20-column width and silently discard every character beyond it, leaving your output truncated and unreadable. The fix is to lock PuTTY's columns and rows, forbid resizing, zero out the window gap, and save those values into the Default Settings profile so every embedded session inherits them. This guide walks through the exact PuTTY in Remote Desktop Manager configuration, explains why the bug happens, and shows how to verify the fix.

The problem: PuTTY collapses to 20 columns inside RDM

Remote Desktop Manager is a popular connection manager for Windows that can host external tools like PuTTY inside its own tabbed interface using a feature called window embedding. RDM reparents the PuTTY window into an RDM panel so your SSH terminals live alongside RDP, VNC, and web sessions in one place.

The trouble starts when several PuTTY sessions are embedded at once. As you click between RDM tabs, RDM repeatedly hides, shows, and resizes the hosted PuTTY window. During those rapid resize events the embedded window can momentarily report a tiny client area, and PuTTY honors it by shrinking its terminal to roughly 20 columns.

Because a terminal is character-grid based, anything to the right of column 20 is not wrapped, it is clipped and lost. Command output, log lines, and even your own typed commands appear cut off. Redrawing or re-running the command does not help, because every new line is generated against the same broken 20-column geometry.

The root cause is the interaction between RDM's resize handling and PuTTY's default behavior of auto-adjusting its terminal to match the window. The cure is to stop PuTTY from resizing at all and to pin a fixed, readable geometry.

Before you start: requirements

This procedure was validated against Remote Desktop Manager 5.8.3, but the same settings apply to current RDM releases and to any setup where PuTTY is embedded in another host window. You will need the following:

• A working PuTTY install (the standard putty.exe from the official PuTTY distribution).
• Remote Desktop Manager with at least one PuTTY-based session, configured to embed the tool inside the RDM tab rather than launch it as a separate floating window.
• Permission to edit PuTTY saved sessions on the machine (PuTTY stores its settings per Windows user in the registry under HKEY_CURRENT_USER\Software\SimonTatham\PuTTY).

The key idea is that PuTTY's Default Settings profile is the template every new and embedded session inherits unless a specific saved session overrides it. By fixing Default Settings, you fix all the embedded terminals at once.

Step-by-step: configure PuTTY in Remote Desktop Manager

Follow these steps in order. You can open the PuTTY configuration dialog either by launching putty.exe directly, or from within RDM by clicking the "..." button next to the PuTTY tool path in the session's properties, which opens the same native PuTTY settings window.

1. Use Default Settings as the base for the RDM session. In the RDM session properties, make sure the PuTTY session loads the Default Settings profile rather than a custom saved session, so the changes you are about to make are picked up.
2. Open PuTTY's configuration dialog. Launch putty.exe, or in RDM open the session's tool properties and click the "..." button to bring up PuTTY's settings.
3. Set a fixed terminal size. Go to Window in the left-hand category tree. Under Set the size of the window, set Columns and Rows to values that fit your RDM panel well. A common, comfortable starting point is 120 columns by 40 rows; if your RDM tab is smaller, try 100 x 30.
4. Forbid resizing completely. Still in the Window category, under When window is resized, select Forbid resizing completely. This is the single most important setting, it stops PuTTY from ever collapsing to 20 columns when RDM fires resize events.
5. Remove the inner padding. Open Window > Appearance and set Gap between text and window edge to 0. This lets the fixed-size terminal use the entire embedded area with no wasted border, so text reaches the panel edges cleanly.
6. Save into Default Settings. Click Session at the top of the category tree. In the Saved Sessions list, select Default Settings, then click Save. This writes your fixed geometry into the template every embedded PuTTY session uses.
7. Close without launching. Click Cancel to close the configuration window. (Clicking Open would start a connection; you only needed to save the profile.)

From now on, every PuTTY terminal you embed in RDM opens at the fixed columns and rows you chose, and switching between embedded PuTTY tabs no longer truncates output.

Why these specific settings work

Each setting targets a distinct part of the failure. Together they make the embedded terminal geometry deterministic instead of reactive.

PuTTY offers three resize behaviors: change the number of rows and columns, change the size of the font, and forbid resizing completely. The first two keep PuTTY chasing the window dimensions, which is exactly what breaks inside RDM. Forbid resizing completely tells PuTTY to keep its character grid constant no matter what the host window reports, which is the behavior you want when another application owns the window frame.

Common pitfalls to avoid

Most failed attempts come down to saving the settings in the wrong place or leaving one piece of the chain un-fixed.

• Saving to a named session instead of Default Settings. If you save your geometry to a session called, for example, prod-server, but RDM launches PuTTY against Default Settings, your fix is ignored. Always confirm what profile RDM actually loads.
• Forgetting to forbid resizing. Setting fixed columns and rows alone is not enough, PuTTY will still try to resize on RDM tab switches. Forbid resizing completely is what locks it.
• Picking a width larger than the panel. If your columns value exceeds what the RDM tab can show, the right edge of the terminal is hidden behind the panel border. Match the columns and rows to the real, usable RDM panel size.
• Editing the wrong Windows user's profile. PuTTY settings are per Windows user. If RDM runs PuTTY under a different account or elevated context, configure PuTTY in that same context, or export and import the saved session.
• Leaving non-zero padding. A large gap value wastes space and can push a fixed-width terminal partly out of view; setting it to 0 avoids that.
• Assuming font scaling helps. Choosing "change the size of the font when resized" seems convenient but reintroduces resize-driven instability; stick with the fixed grid.

Verify the fix is working

After saving Default Settings and closing the dialog, confirm the embedded terminals behave correctly:

1. Open two or more embedded PuTTY sessions in RDM and connect each to a host.
2. Check the reported width. On any Linux or Unix host, run tput cols. It should report the columns value you set (for example 120), not 20.
3. Confirm the full geometry. Run stty size, which prints rows and columns together, and verify both match what you configured.
4. Stress-test tab switching. Click rapidly between the embedded PuTTY tabs several times, then run tput cols again. The value must stay constant, that is proof the resize bug is gone.
5. Run a wide command. Execute something with long output such as ls -l /etc or ps aux and confirm nothing is clipped on the right edge.

If tput cols still returns a small or shifting number, re-open PuTTY's configuration, confirm Forbid resizing completely is selected, and re-save to Default Settings specifically. Then restart the RDM sessions so they reload the profile.

A note on modern alternatives

PuTTY remains a reliable, lightweight SSH client and this embedding fix is fully valid today. That said, if you regularly host terminals inside Remote Desktop Manager, two modern options reduce friction: RDM ships with a built-in SSH/terminal handler that manages sizing internally, and Windows now includes OpenSSH plus Windows Terminal for native command-line SSH outside RDM. For teams standardizing on PuTTY across many embedded sessions, the fixed-geometry approach in this guide is still the simplest way to keep every terminal readable.

Key Takeaways

• The 20-column truncation is caused by PuTTY auto-resizing in response to RDM hiding, showing, and resizing the embedded window during tab switches.
• The decisive setting is Window > When window is resized > Forbid resizing completely, which keeps the terminal grid constant.
• Set fixed Columns and Rows that match your RDM panel, and set the Gap between text and window edge to 0.
• Always save the geometry into Default Settings, because that is the profile embedded sessions inherit.
• Verify with tput cols and stty size after rapid tab switching, the width should stay locked at your chosen value.

Frequently Asked Questions

Why does PuTTY shrink to 20 columns in Remote Desktop Manager?

When PuTTY is embedded, RDM reparents and resizes the PuTTY window each time you switch tabs. PuTTY's default behavior is to resize its terminal to match the window, so a momentary tiny client area collapses it to about 20 columns and clips everything beyond that width. Forbidding resizing in PuTTY stops this.

Where do I save the fixed columns and rows so all sessions use them?

Save them to PuTTY's Default Settings profile. Open the configuration dialog, set your geometry and the resize option, click Session, select Default Settings, then click Save. Embedded RDM sessions inherit from Default Settings, so every terminal picks up the fix.

How do I confirm the terminal width is actually fixed?

Connect to a Linux or Unix host and run tput cols or stty size. The reported width should equal the columns value you set, and it should not change when you switch rapidly between embedded RDM tabs. A wide command like ls -l should display without clipping on the right.

Does this still work on newer Remote Desktop Manager versions?

Yes. The fix was validated on RDM 5.8.3 and the same PuTTY settings, fixed columns and rows, forbid resizing completely, zero gap, and saving to Default Settings, apply to current RDM releases and to any host that embeds PuTTY as an external tool.

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