linux: Disable LEGACY_PTYS to avoid creating numerous unused tty devices
#657
Comments
> A pseudo terminal (PTY) is a software device consisting of two │ > halves: a master and a slave. The slave device behaves identical to │ > a physical terminal; the master device is used by a process to │ > read data from and write data to the slave, thereby emulating a │ > terminal. Typical programs for the master side are telnet servers │ > and xterms. │ > │ > Linux has traditionally used the BSD-like names /dev/ptyxx │ > for masters and /dev/ttyxx for slaves of pseudo │ > terminals. This scheme has a number of problems, including │ > security. This option enables these legacy devices; on most │ > systems, it is safe to say N. Fixes: #657
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It's worth a try, and see what eventually breaks. I guess the minties enable them on demand. |
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On 03/27/18 09:33, Thomas Kreitler wrote:
It's worth a try, and see what eventually breaks.
Other distros are less radical,
Slackware:
CONFIG_LEGACY_PTYS=y
CONFIG_LEGACY_PTY_COUNT=32
Mint:
CONFIG_LEGACY_PTYS=y
CONFIG_LEGACY_PTY_COUNT=0
I guess the minties anable them on demand.
Debian doesn’t set it, so I guess we are pretty safe. Also, it’s what
the Linux kernel developers recommend.
```
$ grep PTY /boot/config-4.9.0-6-amd64
CONFIG_UNIX98_PTYS=y
# CONFIG_LEGACY_PTYS is not set
```
Anyway, only way to find out, is to test it. So, please help.
```
$ sudo bee install -f linux-4.14.30 nvidia_linux-4.14.30-211-390.25-0
$ sudo mxgrub mariux-4.14.30-211
```
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Default is 'Y' so according to our policy we need a reason to disabled it. Kconfig help text says, "This scheme has a number of problems, including security. This option enables these legacy devices; on most systems, it is safe to say N." I'd say that's enough reason, so I agree, lets try to disable it and see who is missing it. |
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theinternet now without CONFIG_LEGACY_PTYS. Terminal Windows and screen are happy. |
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I hope you mean xterm :) |
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Yeah. "windows" not "Windows" :) |
If so, I wonder, why it is defaulted to Y. |
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On 03/27/18 13:27, Donald Buczek wrote:
> Also, it’s what the Linux kernel developers recommend.
If so, I wonder, why it is defaulted to Y.
I guess, nobody sent a patch.
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> A pseudo terminal (PTY) is a software device consisting of two │ > halves: a master and a slave. The slave device behaves identical to │ > a physical terminal; the master device is used by a process to │ > read data from and write data to the slave, thereby emulating a │ > terminal. Typical programs for the master side are telnet servers │ > and xterms. │ > │ > Linux has traditionally used the BSD-like names /dev/ptyxx │ > for masters and /dev/ttyxx for slaves of pseudo │ > terminals. This scheme has a number of problems, including │ > security. This option enables these legacy devices; on most │ > systems, it is safe to say N. Fixes: #657
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No idea, why this was re-open. Did I force push? Anyway, it’s fixed since Linux 4.14.30-211 (commit 7e5443d (linux-4.14.30-211: Unselect |
From https://github.com/scaleway/image-debian/issues/27:
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