diff options
| -rw-r--r-- | man/systemd-nspawn.xml | 48 |
1 files changed, 25 insertions, 23 deletions
diff --git a/man/systemd-nspawn.xml b/man/systemd-nspawn.xml index db3f10c3a2..c0427aa42f 100644 --- a/man/systemd-nspawn.xml +++ b/man/systemd-nspawn.xml @@ -1296,30 +1296,32 @@ <varlistentry> <term><option>--console=</option><replaceable>MODE</replaceable></term> - <listitem><para>Configures how to set up standard input, output and error output for the container payload, as - well as the <filename>/dev/console</filename> device for the container. Takes one of - <option>interactive</option>, <option>read-only</option>, <option>passive</option> or <option>pipe</option>. If - <option>interactive</option> a pseudo-TTY is allocated and made available as <filename>/dev/console</filename> - in the container. It is then bi-directionally connected to the standard input and output passed to - <command>systemd-nspawn</command>. <option>read-only</option> is similar but only the output of the container - is propagated and no input from the caller is read. In <option>passive</option> mode a pseudo TTY is allocated, - but it is not connected anywhere. Finally, in <option>pipe</option> mode no pseudo TTY is allocated, but the - passed standard input, output and error output file descriptors are passed on — as they are — to the container - payload. In this mode <filename>/dev/console</filename> will not exist in the container. Note that in this mode - the container payload generally cannot be a full init system as init systems tend to require - <filename>/dev/console</filename> to be available. On the other hand, in this mode container invocations can be - used within shell pipelines. This is because intermediary pseudo TTYs do not permit independent bidirectional - propagation of the end-of-file (EOF) condition, which is necessary for shell pipelines to work - correctly.</para> - - <para>Note that the <option>pipe</option> mode should be used carefully, as passing arbitrary file descriptors - to less trusted container payloads might open up unwanted interfaces for access by the container payload. For - example, if a passed file descriptor refers to a TTY of some form, APIs such as <constant>TIOCSTI</constant> - may be used to synthesize input that might be used for escaping the container. Hence <option>pipe</option> mode - should only be used if the payload is sufficiently trusted or when the standard input/output/error output file - descriptors are known safe, for example pipes. Defaults to <option>interactive</option> if + <listitem><para>Configures how to set up standard input, output and error output for the container + payload, as well as the <filename>/dev/console</filename> device for the container. Takes one of + <option>interactive</option>, <option>read-only</option>, <option>passive</option>, or + <option>pipe</option>. If <option>interactive</option>, a pseudo-TTY is allocated and made available + as <filename>/dev/console</filename> in the container. It is then bi-directionally connected to the + standard input and output passed to <command>systemd-nspawn</command>. <option>read-only</option> is + similar but only the output of the container is propagated and no input from the caller is read. If + <option>passive</option>, a pseudo TTY is allocated, but it is not connected anywhere. Finally, in + <option>pipe</option> mode no pseudo TTY is allocated, but the standard input, output and error + output file descriptors passed to <command>systemd-nspawn</command> are passed on — as they are — to + the container payload, see the following paragraph. Defaults to <option>interactive</option> if <command>systemd-nspawn</command> is invoked from a terminal, and <option>read-only</option> - otherwise.</para></listitem> + otherwise.</para> + + <para>In <option>pipe</option> mode, <filename>/dev/console</filename> will not exist in the + container. This means that the container payload generally cannot be a full init system as init + systems tend to require <filename>/dev/console</filename> to be available. On the other hand, in this + mode container invocations can be used within shell pipelines. This is because intermediary pseudo + TTYs do not permit independent bidirectional propagation of the end-of-file (EOF) condition, which is + necessary for shell pipelines to work correctly. <emphasis>Note that the <option>pipe</option> mode + should be used carefully</emphasis>, as passing arbitrary file descriptors to less trusted container + payloads might open up unwanted interfaces for access by the container payload. For example, if a + passed file descriptor refers to a TTY of some form, APIs such as <constant>TIOCSTI</constant> may be + used to synthesize input that might be used for escaping the container. Hence <option>pipe</option> + mode should only be used if the payload is sufficiently trusted or when the standard + input/output/error output file descriptors are known safe, for example pipes.</para></listitem> </varlistentry> <varlistentry> |