JEXEC(8)

💅 JEXEC(8) 💅

hey bestie, welcome to JEXEC(8) from the System Manager's Manual — this one is literally about running a command inside a jail that's already up and running. no cap, it's giving "let me just pop into this jail real quick" energy 🫶

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✨ NAME ✨

jexec — execute a command inside an existing jail, periodt 💖

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🦋 SYNOPSIS 🦋

jexec [-l] [-d working-directory] [-u username | -U username] jail
      [command ...]

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🌸 DESCRIPTION 🌸

okay so the jexec utility executes command inside the jail identified by its jid or name. if command is not specified then the user's shell is used. iconic, honestly ✨

the following options are available:

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🎀 OPTIONS 🎀

• -d working-directory — the working directory for running commands inside the jail. the default is the jail root directory. very "set the vibe before you walk in" 💅
• -l — execute in a clean environment. the environment is discarded except for HOME, SHELL, TERM, USER, and anything from the login class capability database for the user. PATH is set to "/bin:/usr/bin". if a user is specified (via -u or -U), and absent the -d option, commands are run from that (possibly jailed) user's directory. clean slate, no baggage, we love to see it 🧚
• -u username — the user name from host environment as whom the command should run. this is the default. host-side user, classic behavior 👑
• -U username — the user name from jailed environment as whom the command should run. jailed-side user, for when you're being extra specific 🔥

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🌈 EXAMPLES 🌈

💜 Example 1: Open a shell in a jail

the following command specifies a jail by its name and utilizes the current user's shell:

# jexec name

it is also possible to specify a jail by its jid:

# jexec JID

🍓 Example 2: Run a single command without opening a shell

the following command runs uname -a in a jail called "name". since a command is specified explicitly, jexec does not spawn an interactive shell. instead, jexec executes the specified command directly. lowkey efficient fr fr ⭐

# jexec name uname -a

🦋 Example 3: Open a shell in a jail with a clean environment

the following command opens a sh(1) shell in a jail with a clean environment:

# jexec -l name sh

👑 Example 4: Open a shell in a jail with the login command

the following command utilizes login(1) to access the jail, submitting an audit record, and displaying the user's last login, system copyright, and motd(5) message:

# jexec -l name login -f root

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💖 SEE ALSO 💖

• jail_attach(2)
• jail(8)
• jls(8)

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⭐ HISTORY ⭐

the jexec utility was added in FreeBSD 5.1. vintage but still slaying 💅

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💀 BUGS 💀

if the jail is not identified by jid there is a possible race in between the lookup of the jail and executing the command inside the jail. giving a jid has a similar race as another process can stop the jail and start another one after the user looked up the jid.

heads up bestie — race conditions are not the cute kind of drama 😭 keep this in mind.

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mwah 💋 this page is brought to you by Debian, dated March 5, 2025, and lives in the System Manager's Manual — catch u later, bestie 🫶